No. 9, March 2005
Filamentary Hα emission in Cygnus, observed as part of the INT WFC Northern Galactic Plane
photometric Hα survey (IPHAS). The colour scheme is red for Hα, blue for the Sloan r ' band, and green
for Sloan i ' band. As this is a significantly reddened region, as well as nebulous, there are many stars
coming through strongly in the i ' band, appearing here as a background of green stars. Colour image
courtesy of Mike and Jonathan Irwin (IoA, Cambridge). For more information see the article by Janet
Drew et al. on page 3.
Message from the Director
Dear Reader,
In the previous issue of this Newsletter I
reported on the initiation of a project for the
development of a Rayleigh laser guide star
beacon, GLAS, for the WHT. Since then much
work has gone into this project, and an
important milestone was passed in January
with the successful completion of the
Preliminary Design Review. The positive
outcome of that review implies that the project
now moves towards the final design stage, and
real money can now be spent on hardware. For
example, the solid-state laser system will be
purchased shortly. GLAS is a complex and
demanding development, with exciting science
prospects that make this project worthwhile;
watch this space !
Another key event that will take place during
the summer of this year is an independent
international review of the ING, commissioned
by the ING Board. The high-profile committee
of four world-renowned astronomers will focus
specifically on the medium-term future of the
observatory. The views of the wider astronomical
community — your view s— will play an
important role, and to that effect a community
questionnaire has been released to provide an
easy input channel. Until May 31st input can
No. 9, March 2005
The Isaac Newton
Group of Telescopes
The Isaac Newton Group of
Telescopes (ING) consists of the
4.2 m William Herschel Telescope
(WHT), the 2.5 m Isaac Newton
Telescope (INT) and the 1.0 m
Jacobus Kapteyn Telescope (JKT),
and is located 2350 m above sea
level at the Roque de Los
Muchachos Observatory on the
island of La Palma, Canary Islands,
Spain. The WHT is the largest
telescope of its kind in Western
The construction of the ING telescopes
was the result of a collaboration
between the United Kingdom and
the Netherlands. The site is provided
by Spain, and in return Spanish
astronomers receive 20 per cent of
the observing time on the telescopes.
The operation of the site is overseen
by an International Scientific
Committee, or Comité Científico
Internacional (CCI).
A further 75 per cent of the
observing time is shared by the
United Kingdom, the Netherlands
and the Instituto de Astrofísica de
Canarias (IAC). The remaining 5
per cent is reserved for large
scientific projects to promote
international collaboration between
institutions of the CCI member
The ING operates the telescopes on
behalf of the Particle Physics and
(PPARC) of the United Kingdom,
the Nederlandse Organisatie voor
Wetenschappelijk Onderzoek (NWO)
of the Netherlands and the IAC in
Spain. The Roque de Los Muchachos
Observatory, which is the principal
European Northern hemisphere
observatory, is operated by the IAC.
(Continued from front cover)
be provided through:
control systems. Charles will be dearly
missed and not be forgotten by his
friends and colleagues. A commemorative
plaque will be located on the WHT.
In this issue of the Newsletter you will
find a fine cross section of science We were equally shocked to hear that
results obtained from the telescopes. Emilios Harlaftis died as the result of a
But let me point you also to the
contributions by S. Hameed that so
nicely captures the excitement of
conducting astronomical observations,
and the one by N. Douglas on a very
special public outreach activity.
I end this introduction with two sad
notes: Our friend and colleague, Charles
Benneker, passed away in October last
year. Charles had worked at the observatory
for over a decade, specialising on
electronics systems and instrument
The ING Board
The ING Board oversees the operation,
maintenance and development of the Isaac
Newton Group of Telescopes, and fosters
collaboration between the international
partners. It approves annual budgets and
determines the arrangements for the
allocation of observing time on the
telescopes. ING Board members are:
Prof J. Drew, Chairperson – ICL
Prof T. van der Hulst, Vice Chairperson –
University of Groningen
Dr G. Dalton – University of Oxford
Dr R. García López – IAC
Dr P. Crowther – University of Sheffield
Dr R. Stark – NWO
Dr C. Vincent – PPARC
Dr S. Berry, Secretary – PPARC
The ING Director’s
Advisory Group
tragic accident. Emilios had spent
several years working at the observatory
as support astronomer. After moving
back to the UK, and later to his home
country, Greece, he always kept close
scientific and personal ties with the
observatory on La Palma. He will be
remembered for his contribution to
science and his unconditional enthusiasm
for astronomy and the observatory.
René G. M. Rutten
The ING Newsletter
ISSN 1575 –8958 (printed version)
ISSN 1575 –9849 (electronic version)
Legal License: TF–1959/99
Published in Spain by THE ISAAC
Apartado 321; E-38700 Santa Cruz de
La Palma; Canary Islands; Spain.
Telephone: +34 922 425400
Fax: +34 922 425401
Editorial team: Javier Méndez, René
Rutten and Danny Lennon.
Consultant: Johan Knapen.
Designer: Javier Méndez.
Preprinting: Gráficas El Time.
Printing: Gráficas Sabater.
The Director’s Advisory Group (DAG)
assists the observatory in defining the
strategic direction for operation and
development of the telescopes. It also
provides an international perspective and
acts as an independent contact point for
the community to present its ideas. DAG
members are:
The ING Newsletter is primarily published
on-line at
newsletter/ in HTML and PDF format.
Notification of every new issue is given
by e-mail using the [INGNEWS] mailing
list. More information on [INGNEWS]
can be found on page 32. Requests for
one-off printed copies can be emailed to
Javier Méndez ( jma @
Dr M. McCaughrean, Chairperson –
Astrophysikalisches Institut Potsdam
Dr M. Balcells – IAC
Dr P. A. James – Liverpool John Moores Univ.
Dr N. Tanvir – Univ. of Hertfordshire
Dr E. Tolstoy – Univ. of Groningen
The ING Newsletter is published twice a
year in March and September. If you
wish to submit a contribution, please
contact Javier Méndez ( [email protected]).
Submission deadlines are 15 July and
15 January.
No. 9, March 2005
IPHAS: Surveying the Northern Galactic Plane in Hαα
J. E. Drew1, D. J. Lennon2, R. Greimel2, A. Zijlstra3, J. Irwin4, A. Aungwerowijt 5, M. J. Barlow5,
R. Corradi2, C. J. Evans 2, B. Gaensicke6, P. Groot7, A. Hales 5, E. Hopewell1, M. J. Irwin4,
M. Jaigirdar 2, C. Knigge8, P. Leisy 2, A. Mampaso 9, M. Matsuura3, L. Morales Rueda7, R. Morris 10,
Q. A. Parker11, S. Phillipps10, P. Rodríguez Gil9, G. Roelofs7, I. Skillen2, D. Steeghs12, Y. C. Unruh1,
K. Viironen 9, J. Vink1, N. A. Walton4, A. Witham 8, N. Wright5, A. Zurita13
1: Imperial College London; 2: Isaac Newton Group of Telescopes; 3: Manchester University; 4: CASU, Cambridge; 5: University
College London; 6: Warwick University; 7: Nijmegen University, The Netherlands; 8: Southampton University; 9: Instituto de
Astrofísica de Canarias; 10: Bristol University; 11: Macquarie University, Australia; 12: Harvard-Smithsonian Centre for Astrophysics,
USA; 13: Granada University, Spain.
α emission is ubiquitous in
our Galaxy. It traces ionised
gas of assorted nebulae such
as HII regions, planetary nebulae,
Wolf-Rayet nebulae, and supernova
remnants. It is a strong signature of
active stars, interacting binaries, very
massive stars (especially supergiants,
Luminous Blue Variables and WolfRayet stars), Be stars, post-AGB stars,
pre-main-sequence stars and so on.
These objects represent important
evolutionary phases which are
generally short lived, and are hence
few in number and difficult to find.
Their discovery is therefore well
worth the effort of a concerted
programme and in August 2003 a
major new survey project was started
using the Wide Field Camera (WFC)
on the Isaac Newton Telescope (INT)
to do just that. It is called the INT
Photometric Hα Survey of the Northern
Galactic Plane, or IPHAS for short.
IPHAS is a collaborative UK/NL/ES
venture led by Janet Drew in UK, Paul
Groot in The Netherlands, and Antonio
Mampaso in Spain. Its goal is to
conduct an Hα survey of the entire
northern Galactic Plane in the latitude
range – 5°< b< +5°, a sky area of 1800
sq. deg., covering the magnitude range
13 < r'< 20. That such a survey is
needed can be deduced from Figure 2,
and when complete it will represent an
enormous improvement over previous
work. For example it is expected that
in excess of 10,000 new emission line
Figure 1. The crescent nebula, NGC6888, which surrounds the Wolf-Rayet star PPM
84423, seen in Hα emission by IPHAS. Colour image courtesy of Jonathan Irwin.
stars alone will be discovered, an order
of magnitude increase on known
Survey Details
The 1800 square degrees will be tiled
with 7635 pointings of the WFC, each
of which is paired with a second
pointing at an offset of 5 arcmin W and
S. The purpose of the offset field is to
ensure that we cover stars in the gaps
between detectors, but also means that
the majority of sources are observed at
least twice. Each field is to be observed
with the Sloan r' and i' filters, plus a
narrow band Hα filter, with exposure
times of 30s, 10s and 120s respectively.
The use of a guide star is not necessary
for such short exposure times and is
dispensed with to save on overheads,
while for each Hα – r'– i' sequence at
a given pointing the CCD readout,
filter movements, and final telescope
movement, are overlapped for
additional savings. Finally, human
No. 9, March 2005
Figure 2. The left-hand panel illustrates the effect of a simple extrapolation of numbers of catalogued emission line stars from
previous Hα surveys of Kohoutek & Wehmeyer (1999) in the north, and Stephenson & Sanduleak (1971) in the south. Based on
a rough extrapolation of these earlier surveys it is estimated that of order ~10 4 emission line stars will be discovered. The central
and right-hand panels compare the quality of the current IPHAS colour-colour diagrams with those for the same sky area taken
from the UK Schmidt southern Hα photographic survey. Notice the superb delineation of the field population of normal stars and
M dwarfs in the IPHAS data (cf. Figure 3).
interaction is avoided as much as
possible by the use of automatic
observing scripts, which typically run
for about 3 hours, broken only to take
standard star observations.
All data are transferred using external
discs to the Cambridge Astronomical
Survey Unit (CASU) where they are
processed using the CASU pipeline:
calibration steps consist of bias
correction, flat-fielding, de-fringing,
astrometric solution, flux calibration
and object catalogue generation (see
the article by Irwin et al. on WFS in
this issue). Work is progressing on the
construction of a unified object
catalogue and flux calibration for the
complete survey, with an expected
first data release of final data products
expected in early 2006. It is hoped that
completion of the full survey will occur
during 2006, with the full data release
coming during 2007.
Some Expected Science
Strong Hα emission line stars are of
course reasonably easily selected from
the sample since they are well
separated from the bulk population in
the (r'– i', r'– Hα) diagram. Indeed an
initial blue selection of such objects has
already been made using the 2003 data
and some subsequent follow-up
spectroscopy has revealed the vast
majority of these to be Be-like stars,
with a sprinkling of CVs, compact
PN, potential luminous blue
supergiants and the odd QSO (Figure 3).
Figure 3. Sampling the Hα zoo as discovered by IPHAS. Clockwise from top left; a
typical Be star, a cataclysmic variable, a potential luminous blue supergiant in Cygnus
and a low redshift QSO (the QSO was detected as a peculiar outlier in the colourcolour plane).
Not all emission line objects are as
easily discovered however and it is
crucial that effort is put into
understanding the IPHAS colour-colour
plane so that future object selections
can be made with some confidence.
This problem has been attacked on
two fronts; through the construction of
synthetic photometry using a library of
observed flux-calibrated stellar spectra,
and by conducting spectroscopic
surveys of selected fields as a visual
check on predicted spectral types.
Figure 4 illustrates the result of this
process for a sample field in Cygnus.
Several thousand spectra in a number
of selected fields have now been
amassed using Hectospec on the MMT
and AF2 on the WHT. In general this
demonstrates that the synthetic
photometry is well matched to the
observations, although detailed studies
of this field, and additional test fields
indicate that some further investigation
of the calibration for very red objects
is required.
IPHAS is also producing new
discoveries of nebulae, one of the first
to be discovered has been named after
the wedding of Su Alteza Real El
Príncipe de Asturias Don Felipe de
Borbón with Doña Letizia Ortiz
Rocasolano which took place around
No. 9, March 2005
Figure 4. Left-hand panel shows the simulated positions of the unreddened main sequence (black), giant (red) and supergiant
(red) stars in the (r'– i', r'–Hα) plane according to spectral type. The right-hand panel shows the observed sources in a field in the
Cygnus region (black points), with some spectroscropically determined spectral types overplotted in colour; light blue points are
early-type stars, red points are mostly G and K stars, while dark blue points are M stars. The magenta points are strong Hα
absorbers, in fact they are white dwarfs, while the green points are emission line stars, in fact Be stars. Note that the trend from
early-type to late-type stars is well reproduced by the synthetic colours (there is a zero point offset due to extinction which drives
stars diagonally upward and to right this diagram). The central gap in the spectroscopic sample is simply a selection effect due to the
algorithm used to select targets for follow-up. All spectroscopy for this field was carried out using Hectospec on the MMT.
the time of the PN’s discovery. PNG
126.62+1.32 is a rare quadrupolar
nebula, and it was spectroscopically
confirmed as a PN in 2004 using the
WHT. A deeper image, compared to the
discovery image, is shown in Figure 5,
which illustrates the initially
undetected faint lobes of the nebula.
Besides looking for new nebulae,
IPHAS has proved to be exceptionally
useful for taking a new look at
previously known nebulae; ING users
may be familiar with the image of
the Wolf-Rayet NGC6888 which
adorned the ING Christmas card in
2004 (Figure 1). However Figure 6
shows the spectacular 5°×3.5° mosaic
of images covering the supernova
remnant S147. Bear in mind that this
image, which is binned for the purposes
of this article, has immense detail on
the arcsecond scale.
To date the survey is approaching its
half-way point in terms of completed
fields. However as we look forward to
the completion of the northern
hemisphere survey it’s clear that we
are already seeing new discoveries, and
generating additional exciting ideas
for follow-up science and data mining.
For example the colour-colour plane
morphologies across the Galactic Plane
will provide useful insights into the
structure of the northern Milky Way,
while linking IPHAS photometry with
JHK survey data from 2MASS and the
UKIDSS Galactic Plane Survey will add
further powerful diagnostic capabilities.
Survey area: ~1800 sq deg in 2×7600 overlapping
Region: – 5° < b < +5° , 25° < l < 225°
Depth: 13 < r' < 20
We thank the many observers who
have contributed to this programme.
Finally, for more complete details
interested parties should refer to the
first survey paper which is currently
in preparation (Drew et al., 2005, to
appear in MNRAS), and to the IPHAS
home page at
Research/Halpha/North/. ¤
Seeing: < 1.7 arcsec
WFC pixel size: 0.33" × 0.33"
WFC field size: ~0.25 sq deg in four 2k×4k CCDs
Filters: r' : λc=6420 Å, FWHM = 1347 Å, t exp =30 s
i' : λc= 7743Å, FWHM = 1519Å, t exp=10s
Hα: λc=6568 Å, FWHM= 95 Å, t exp =120 s
Janet Drew ([email protected])
Table 1. IPHAS essentials.
Figure 5. Left: The newly discovered Planetary Nebula
PN 126.62+1.32, the ‘Prince of Asturias’, is a rare
quadrupolar nebula (central region), with extended
fainter lobes extending over 16 arcminutes from the
central star. Top: Publicity version of the discovery image.
Figure 6 (next two pages). A 5° × 3.5° mosaic of the
supernova remnant S147 in Hα. North is to the top
and East to the left. Courtesy of Albert Ziljstra and
Jonathan Irwin.
No. 9, March 2005
Wide Field Survey: Final Data Products
M. Irwin, R. McMahon, N. Walton, E. González-Solares, S. Hodgkin, J. Irwin,
J. Lewis (IoA, Cambridge)
e present the final data
products from the Wide Field
Survey and the online
database access to them.
1. The INT Wide Field
Major survey programmes covering a
variety of wavelengths are the
mainstay of observational astronomy.
Recent highlights include the Two
Micron All Sky Survey (2MASS) project
which has covered the entire sky at a
resolution of 4 arcsec in the JHK bands
and the Sloan Digital Sky Survey (SDSS;
York et al., 2000;
which covers large areas of the
Northern Hemisphere, with the goal
of covering one quarter of the sky.
These wide area surveys are having a
significant impact, both as target
selectors for 8m class telescopes and for
inherent survey science programmes.
The INT WFS provides deeper data
than the SDSS covering significant
areas of the sky, with many fields being
observed by comparable facilities at
other wavelengths.
The INT WFS has been using the Wide
Field Camera (with a field of view of
the order of 0.3 deg 2) on the 2.5m Isaac
Newton Telescope (INT). The survey
proposal was approved by the Joint
Steering Committee in October 1997
with a subsequent ‘Announcement of
Opportunity’ closing in March 1998.
The WFS International Review Panel
approved three main programmes in
the first year with subsequent review
and continuation into the following
years. The project was initiated in
August 1998 with duration of up to
five years. The WFS is an umbrella
for competitively judged science
programmes which were assessed on
the usual criteria plus the wider worth
of the data set and the management
competence of the proposing teams.
Multicolour data have been obtained
over several square degrees to a typical
depth of ~ 25 mag (U through Z).
Importantly, the data have been
publicly accessible by the UK and
NL communities from day one, with
access to the rest of the world after
one year. The processing and
calibration (up to object catalogue
generation) is the responsibility of the
WFS project.
1.1 WFS Programmes
The main science programmes were
chosen to provide a wide area survey
programme, a more focused but deeper
smaller area programme, and a
programme to address time variability.
In the second period of observations
two more programmes were selected.
The INT Wide Angle Survey (WAS;
R. McMahon, M. Irwin, N. Walton) is
the largest approved programme and
includes sub-projects ranging from
determination of cosmological
parameters (e.g. via SN Type Ia
studies) to searches for Solar System
objects. It is the umbrella programme
for the WFS project and leads
coordination with the other
programmes on, for instance, field and
filter selection to maximise the
scientific leverage of the project.
The WAS additionally incorporates two
distinct science programmes in the
summer semesters centred on Virgo
and the equatorial strip of the North
Galactic Cap:
— A multicolored large area survey of
the Virgo cluster (J.I. Davies) which
aims to obtain the luminosity
function (LF) of Virgo galaxies
(using the U, g', Z filters) as a
function of colour and position in
the cluster from L* to the luminosity
of local dwarf spheroidals.
— The Millennium Galaxy Catalogue
(MGC; S. Driver —see
was a 37.5 deg 2, medium deep, Bband survey, covering a 35 min wide
strip along the equator from 10 h
00 m to 14 h 45 m. The limiting
magnitude is B =26 mag/arcsec2.
Deep UBVRI Imaging Survey with
the WFC (G. Dalton) of four contiguous
regions of 10 deg2 to a limiting
magnitude of B =26 and I =24.5. It
enables the study of the evolution of
galaxy clustering as a function of colour
at faint magnitudes and provides a
catalogue of rich galaxy clusters at
intermediate red-shifts. Furthermore,
quasars can be detected at z >5. In
good seeing, observations of two 5 deg2
fields to U =26 were observed to
investigate clustering of Lyman-break
galaxies at z >3.
The Faint Sky Variability Survey
(FSVS; van Paradijs — see
searched an area of ~20deg2, studying
photometric and astrometric variability
on scales of one hour to a year to a
magnitude of V =25. Example areas
of investigation include: the evolution
of specific Galactic populations (e.g.
CVs, RR Lyraes, halo AGB stars,
brown and white dwarfs, Kuiper Belt
objects, sdB stars), the structure of
the Galactic halo, statistics of optical
transients related to gamma-ray
bursts, and deep proper motion studies.
The Local Group Census (N. Walton
— see
WFS/LGC/) was a deep narrow band
(Hα, [OIII], [SII], HeII) image survey of
all Local Group (LG) galaxies in the
Figure 1. Location of the WFS fields.
northern hemisphere MV brighter than
–14. Old and new emission line
populations (e.g. planetary nebulae
(PNe), HII regions, LBVs, symbiotic
stars) were the main targets of interest.
Complementary broad band data were
obtained to enable the study of linkages
between stellar populations (e.g. AGB
to PNe).
As far as PNe are concerned, the LGC
observations have been fully exploited,
providing a much more complete view
of the PN population of the LG than
previously known, especially for dwarf
galaxies. Details are presented by
Corradi et al. (2003) and in the five
refereed papers and many
contributions at international
conferences published so far (including
the invited review in the first workshop
entirely dedicated to extragalactic
PNe, held in Garching on May 2004).
The PNe discovered by the LGC
allowed discussion of the use of PNe
as luminosity indicators in external
galaxies and in the intergalactic space,
and form a valuable database for
(ongoing) follow-up spectroscopy to
determine their physical and chemical
properties. This allow us to discuss
stellar and galactic evolution over the
large range of metallicites covered by
the LG galaxies.
An Imaging Programme for the
XMM-Newton Serendipitous X-ray
Sky Survey (M.G. Watson— see
data_release/xid_data/) obtained
multi-colour optical imaging of ~ 200
fields drawn from the XMM-Newton
Serendipitous X-ray survey
programme. The INT data has provided
an optical catalogue for ~20,000 X-ray
sources over 25 deg 2.
1.2 Pipeline Processing
The WFS data was fully processed by
the Cambridge Astronomical Survey
Unit (CASU) at the IoA. A detailed
description of the pipeline processing
carried out is found in (Irwin & Lewis,
2001) and is briefly summarised here.
The data is first debiased, bad pixels
and columns are flagged and recorded
in confidence maps which are used
during catalogue generation. The CCDs
No. 9, March 2005
Figure 2. INT Wide
Field Survey main
page at CASU.
are found to have significant non
linearities so a correction using lookup-tables is applied to all data. Flatfield
images in each band are constructed
by combining multiple sky flats
obtained in bright sky conditions
during twilight. Master fringe frames
are created by combining all the science
exposures for each band and used to
correct the images (i' and Z bands
only). Finally an astrometric solution
is applied which results in an internal
astrometric precision better than 100
mas over the whole WFC array. Global
systematics are limited by the precision
of the APM and PMM astrometric
catalogue systems and are at the level of
250mas. The data are photometrically
calibrated using a series of Landolt
standard stars. Data from non
photometric nights are flagged by the
pipeline and each area is calibrated
using the overlap regions (~ 10 %)
between pointings.
Object detection is performed in each
band separately using a standard
APM-style object detection and
parametrisation algorithm. Standard
aperture fluxes are measured in a set
of apertures of radius r /2, r, √2r, 2r,
2√2r where r = 3.5 pixels (the median
seeing — 1 pixel equals 0.333 arcsec)
and an automatic aperture correction
based on the average curve-of-growth
for stellar images is applied to all
detected objects.
A number of key quality control
performance measures are extracted
on a nightly basis from the generated
object catalogues. These indicators
include instrumental information
such as sky brightness, image quality
(ellipticity, FWHM) and throughputs
from extraction of standard star fluxes
and comparison with known zero
point data. More details about the
data products and the format of the
catalogues can be found in the CASU
web page (Figure 2;
2. Final Data Products
All the processed INT WFS data are
available online through a PostgreSQL
database derived from an ingest of the
FITS header contents including the
derived data quality control
information. FITS header information,
including quality control parameters,
are ingested on a regular basis, and a
series of flat files point to the processed
object catalogues and image data. This
has allowed us to offer optional further
processing stages driven from a survey
Data Quality Control (DQC) database.
The main DQC interface is accessible
from the WFS web page at CASU and
provides a large number of search
options (RA, Dec, run number, object
name, observation date,...) and
constraints (airmass, exposure time,
filters, seeing,...). Figure 3 shows an
example query in which the RA and
Dec coordinates of a particular object
are inserted into the form.
The data query returns a table with all
the images that satisfy the constraints.
All those fields which contain the
search position are selected by default
(see Figure 4). A range of visualisation
options are available from here. It is
possible to display image cutouts
around the selected position (eg.
Figure 7) with optional overlay of
already predefined catalogues (the
WFS catalogue, FIRST, 2MASS and
IRAS catalogues are also available) and
user supplied catalogues. It is also
possible to display the whole CCD or
No. 9, March 2005
the mosaic of all CCDs as well as view
the catalogues in various formats (see
Figures 5 and 6) with the federation
between them being done on the fly.
A registration script is built into the
browser for those who wish to access
the facilities offered therein.
Finally the interface allows the
automatic retrieval and downloading
of catalogue and image products; the
ability to group and remotely process
images using CASU facilities including
the CASU VDFS (Vista Data Flow
System) image subtraction, image
stacking and image mosaicing
software utilities and retrieval of the
results etc. (Figure 8).
2.1 The INT WFS Legacy
The WFS archive contains 3.5 Tb of
reduced and calibrated imaging data
online corresponding to about
1200 deg 2. The use of such database
extends beyond the original proposal
programmes described in section 1 and
highly increases the value of the WFS
as a legacy survey. Several of the fields
observed are located in very well
known regions of the sky. For example
the 9 deg2 observed in each of the two
northern areas covered by the
European Large Area ISO Survey
(ELAIS) have been essential to
characterise the population of infrared
sources detected (Rowan-Robinson et
al., 2004). Furthermore, these two
regions have been observed in the midand far-IR by the Spitzer Wide-area
Infrared Extragalactic Survey (SWIRE;
Lonsdale et al., 2003). The WFS optical
data have been used to provide the
optical identifications of the infrared
sources detected and have been also
included in the first SWIRE data
Figure 3. Example query of images in a search box of 20 arcmin around a RA, Dec
position. All images observed in the U, g', r', i' and Z are requested if the seeing is better
than 2'' and they have been observed at an airmass lower than 1.5. No other constraints
have been imposed, but the run number, object name, observation date, exposure
time among others have been selected to be displayed into the ouput table.
Figure 4. Returned query listing the available images. Those fields with the search
pointing on the CCD are selected by default.
3. Summary
The INT WFS programme is now
completed. All the data is available
online from the CASU WFS web page
at IoA. Data cutouts, image catalogues
and science images are available from
this access point. The database also
supports on the fly multipassband
merging of catalogues and optional
Figure 5. Display options available. Note the ‘Overlay object catalogues’ box is updated
with one user supplied catalogue; sources in that catalogue can be displayed in the
image cutouts as well as be federated with the other catalogues.
No. 9, March 2005
Figure 6 (left). Example catalogue federation output for one source (display rearranged due to page size limits). Together with the
WFS optical magnitudes, also the magnitudes from 2MASS are displayed as the properties from our user supplied catalogue.
Figure 7 (right). Example cutouts in different wavebands returned from the DQC query around our selected source with object
catalogues overlaid.
federation with user supplied
catalogues as well as image mosaicking
and stacking. The INT WFS imaging
data has also been used by external
programmes. ¤
Corradi, R., et al., 2003, ING Newsl., 7, 14.
Irwin, M., Lewis, J., 2001, New Astronomy
Reviews, 45, 105.
Lonsdale, C. J., et al., 2003, PASP, 115, 897.
Rowan-Robinson, M., et al., 2004, MNRAS,
351, 1290.
York, D. G., et al., 2000, AJ, 120, 1579.
Mike Irwin ([email protected])
Figure 8. Data retrieval form. We have selected to retrieve the catalogues from all the
images as well as per band stacked images. Note that two of the images and catalogues
are not available to the user because they are propietary.
Direct Detection of Giant Exoplanets
J. A. Caballero (IAC), V. J. S. Béjar (Proyecto Gran Telescopio Canarias, IAC)
ince the discovery in 1995 of the
first extrasolar planet candidate
around a solar type star using
the radial velocity method (Mayor &
Queloz, 1995), to date (beginning of
2005), 135 candidate planets around
main sequence stars have been
discovered by the transit and the radial
velocity (RV) methods. Their minimum
masses are in the range 0.045 to
13 MJup. The proximity of these planets
to their host stars has prevented
direct imaging and spectroscopy,
making a precise characterisation of
their physical structure and chemical
composition difficult.
The least massive objects imaged and
spectroscopically confirmed outside the
Solar System are the so called isolated
planetary-mass objects (IPMOs)
discovered in the σ Orionis cluster
(age ~3 Myr, distance ~350 pc), with
masses in the range 3 – 13 M Jup
(Zapatero Osorio et al., 2000, 2002;
Béjar et al., 2001). Very recently,
Chauvin et al. (2004) have announced
the discovery of a ~ 5M Jup object at a
projected separation of 55 AU of a
brown dwarf of the TW Hydrae
association (age ~ 8 Myr, distance
~70 pc). This object awaits confirmation
by proper motion studies and high
signal to noise spectroscopy. Slightly
No. 9, March 2005
more massive is G196-3B, a substellar
companion of a young nearby M dwarf
(Rebolo et al., 1998). Its mass could
be significantly lower than 25 M Jup if
the age of the system is confirmed to
be much less than 100 Myr (McGovern
et al., 2004).
The JOVIAN Project
The aim of the JOVIAN project
(Jupiter-like Objects in the Visible
and in the Infrared: their Astrophysical
Nature; P. I.: R. Rebolo) is to achieve
the direct detection and characterisation
of objects down to the mass of Jupiter,
and help, through selected observations,
to shed light on the formation of
massive planets.
In the last six years we have followed
two major strategies for direct detection
of such objects: wide field imaging
searches for 1 to ~ 13 M Jup objects in
several very young open clusters; and
high spatial-resolution imaging, with
Adaptive Optics (AO) or the Hubble
Space Telescope (HST), of young
nearby late-type stars in the solar
neighbourhood (age 600 – 30 Myr,
distance < 50 pc). In both strategies,
youth is a key parameter given the
large overluminosity of ultra-low mass
objects during the contraction phase.
We summarise below some of the
results achieved in the ongoing
JOVIAN project.
IPMOs in the σ Orionis
The σ Orionis cluster has revealed as
a paradigmatic place for understanding
the formation of stellar and substellar
objects. Following our first discoveries
of massive brown dwarfs (50–30MJup)
in the120 Myr-old Pleiades cluster
(Rebolo et al., 1995, 1996), we decided
to investigate in a much younger
cluster the formation of less massive
objects down to the deuterium burning
limit. The region around the multiple
stellar system σ Orionis was selected
because of its proximity, youth and
low extinction. We have conducted RIZ
surveys with the IAC-80 telescope
(Observatorio del Teide) and the Wide
Field Camera at the Isaac Newton
Figure 1 (left). JHKs composite image of the G 196-3AB system. The images were
taken with the NAOMI+INGRID Adaptive Optics system at the William Herschel Telescope.
North is up and East is left. Size is 41 arcsec× 41 arcsec. G 196-3A, an extremely
young nearby M star, is in the centre of the field of view. G 196-3B, 13.5 arcsec to the
SWS, is a late L spectral type brown dwarf that shares common proper motion with
the A component. Estimated mass of G 196-3B is 25 MJup or less. These images are
sensitive to discover superjupiters at separations >
~ 50 AU to the central star.
Figure 2 (right). Same as previous figure, but for the V639 and V647 Herculis system.
The double object at 6.5 arcsec SSE of the brightest star is a blue background object
of unknown nature. It does not belong to the stellar system. The FWHM of the JHKs
images is better than 0.2 arcsec.
Telescope (Observatorio del Roque de
los Muchachos). From these surveys
we covered the whole brown dwarf
domain. Most of the one hundred
brown dwarf candidates discovered
were confirmed as bona fide cluster
members, by follow-up near-infrared
photometry and optical spectroscopy.
Many of them have been confirmed
using the ISIS spectrograph at the
William Herschel Telescope or LRIS
at Keck Observatory.
2000/3.5m Calar Alto). From the new
processed data we have identified
about 15 new cluster member
candidates with masses in the
planetary domain. Our faintest
candidate, S Ori 70, resulted from a
JH-band mini-survey performed with
INGRID at the WHT. Near-infrared
low-resolution spectroscopy obtained
at the Keck Observatory led us to
derive a T6 spectral type and a mass
in the range 2 to 8 MJup.
From these studies we have
characterised the complete spectral
sequence of the cluster in the brown
dwarf domain from spectral type M6
to L1.5 (roughly 75 MJup to 13 MJup).
We have found that the substellar
mass spectrum increases toward
lower masses and can be represented
by a power-law, dN/dM ~M– 0.8±0.4
(Béjar et al., 2001). Our results
indicate that brown dwarfs are very
common in the cluster and suggest
that a similar behaviour of the mass
spectrum is possible at lower masses.
Substellar Companions of
In order to detect fainter and less
massive objects, we have performed
and planned to conduct deeper surveys
in the optical ( I band, using the Wide
Field Camera) and in the near-infrared
(JHKs bands,with ISAAC/VLT,
In order to detect faint cool companions
of young nearby stars, we have used
the NICMOS instrument with the
coronograph at the HST and AO
systems attached at 4 m-class
telescopes: Alfa+Omega-Cass at the
3.5-m Calar Alto, [email protected]+NICS
at Telescopio Nazionale Galileo and,
especially, NAOMI+INGRID at the
WHT. The data taken by our group
allow to resolve faint objects down to
separations of ~ 1 arcsec of relatively
bright stars. This separation in a
stellar system at 10 pc corresponds to
~ 10 AU. The sensitivity to planetarymass companions improves when the
spatial resolution is higher (i.e. nearby
stars) and the contrast is lower (i.e.
No. 9, March 2005
primaries are low-mass stars and
planets are intrinsically brighter due
to youth).
We are studying more than fifty stellar
systems closer than 50pc, with spectral
types later than solar and with features
indicative of youth (high lithium
abundance, X-ray and/or UV emission,
membership to young proper motion
associations, etc.). The ages of the
stellar systems range between 30 and
600 Myr. Forty of them have been
completely analysed, comparing first
and second astrometric epochs and
performing photometry when possible.
Although the data would allow us to
discover objects with masses down to
3–10 M Jup in several of the systems,
we have not detected any previously
unknown substellar companion at
distances between ~30 and ~1000 AU
of the primaries. We have only detected
two, possibly three, stellar companions
in very close orbits and a previously
known L-type dwarf secondary. From
our study, the frequency of substellar
companions at intermediate and
large separations of the primary
stars is < 4 %.
This apparently disappointing result
is of great interest, since together with
work performed by other authors,
allows to conclude that only ~ 1 % of
the solar-like stars have massive
planetary companions and brown
dwarfs at intermediate and large
distances (e.g. McCarthy & Zuckerman,
2004). This figure must be compared
with the 7.3±1.5% of the solar-like
stars that have exoplanet candidates
discovered at small separations with
the RV method.
Figure 3. The σ Orionis region and the WFC surveys. The bright star to the up left
corner (North East) is Alnitak, one of the stars of the Orion Belt. Blue background: Iband image from Digitised Sky Survey. Coloured intermediate level: WFC survey in
VRI-bands (note the emission in R band (or Hα) of the nebula associated to Alnitak
and the Horsehead Nebula). Grey foreground: very deep I-band WFC survey (Ilim
about 24.5).
Future Prospects
The ultimate goal of the JOVIAN
project is to set observational
constraints on the scenarios of
formation of giant planets with masses
from 1 to ~13 MJup (jupiters and
superjupiters). These objects appear
to be quite abundant, as they exist at
close distances of relatively old solarlike stars, but also free floating in very
young open clusters. Is the lack of
massive giant planets at intermediate
and large distances related to the
Figure 4. Pictorical view of several isolated planetary-mass objects (IPMOs) in the σ
Orionis cluster (Zapatero Osorio et al., 2000).
No. 9, March 2005
existence of IPMOs? Is there any
scenario that could explain
qualitatively and quantitatively the
observational features? Are IPMOs the
result of direct collapse and
fragmentation of clouds? These
questions will also be addressed by the
JOVIAN project using the first light
instruments of the Gran Telescopio
Members of the JOVIAN project at
Instituto de Astrofísica de Canarias:
R. Rebolo, E. Martín, V. J. S. Béjar,
J. A. Caballero, G. Bihain and J.
Licandro (also at ING); LAEFF/INTA:
M. R. Zapatero Osorio and D. Barrado
y Navascués; Universidad Politécnica
de Cartagena: A. Díaz, A. Pérez and
I. Villo; Max-Planck-Institut für
Astronomie: C. Bailer-Jones and R.
Mundt; Thüringer Landessternwarte
Tautenburg: J. Eisloeffel.
More information on JOVIAN can be
found at
jovian/. ¤
Figure 5. Nearinfrared image of S
Ori 70 (marked with
two lines),
overimposed onto a
Digitised Sky Survey
image centred in the
multiple stellar system
σ Orionis, that gives
the name to the
cluster. The mass of
S Ori 70 is calculated
to be in the range 2
to 8 Jupiter masses.
Rebolo, R., et al., 1995, Nature, 377, 129.
Béjar, V., et al., 2001, ApJ, 556, 830.
Rebolo, R., et al., 1996, ApJ, 469, L53.
Chauvin, G., et al., 2004, A&A, 425, L29.
Rebolo, R., et al., 1998, Science, 282, 1309.
Mayor, M., Queloz, D., 1995, Nature,
378, 355.
Zapatero Osorio, M. R., et al., 2000, Science,
290, 103.
McCarthy, C., Zuckerman, B., 2004, AJ,
127, 2871.
Zapatero Osorio, M. R., et al., 2002, ApJ,
578, 536.
McGovern, M. R., et al., 2004, ApJ, 600,
José A. Caballero ([email protected])
LIRIS Observations of SN 2004ao
G. Gómez (IAC), R. López (Departament d’Astronomia i Meteorologia, Universitat de Barcelona),
J. Acosta-Pulido (IAC), A. Manchado (IAC)
he knowledge of the properties
of supernovae (SNe) at optical
wavelengths has experienced
enormous progress in the current
decade. In contrast, comparatively
little is known about the SN behaviour
in the near-infrared (NIR) window.
Such a knowledge would give us
relevant clues to key questions related
to the nature of SN progenitors and to
the interaction with SN environments.
Hence, programs for NIR
spectrophotometry of SNe of all
supernova types are clearly useful, and
the Long-Slit Intermediate Resolution
Infrared Spectrograph (LIRIS) could
be a good choice (see Acosta-Pulido et
al., 2002, 2003, for more details on
the instrument).
hydrogen-naked massive star.
However, it is still a matter of debate
whether these two SN types (Ib and
Ic) constitute two completely separate
classes of events, produced by different
classes of progenitors or, on the
contrary, both SN types correspond to
variations within a more or less
continuous sequence of core-collapse
SNe (Matheson et al., 2001; Hamuy
et al., 2002). It should be emphasised
that the main distinguishing difference
between the Type Ib and the Type Ic
SNe is based on the strength of their
optical HeI lines: these lines are clearly
present in the SNe Ib optical spectra,
whereas these lines appear weak, or
even are absent in Type Ic SN optical
Currently, the most widely accepted
scenario to explain the SN types Ib
and Ic involves the core-collapse of a
The He abundance in Type Ib/c SN
atmospheres is critical for deciding
between alternative progenitor models.
It should be noted that the He I
λ10830 line is strong even in the case
of weak He I lines at optical wavelengths
(Jeffery et al., 1991). Thus, this NIR
He I line is a more sensitive tracer of
small amounts of He (Wheeler et al.,
1993). In this sense, NIR spectra of
SN types Ib and Ic could be a very
useful tool to better establish the He
abundances in these objects.
SN 2004ao, in UGC 10862, was
discovered on March 7.54 (Singer &
Li, 2004). The supernova lies close to
the southern arm of its host galaxy.
From an optical spectrum obtained on
March 14.53 the supernova was
classified as a Type Ib approximately
one week after maximum (Matheson,
Challis & Kirshner, 2004). SN 2004ao
was fairly bright at the date of its
discovery (V~15; Singer & Li, 2004),
thus we decided that this target could
No. 9, March 2005
be appropriate to get useful results
with the scheduled LIRIS configuration
without a high cost in observing time.
Here we present the first NIR
observations of Type Ib SN 2004ao, that
we performed as a test of the LIRIS
capabilities for SN spectrophotometry
in the NIR window.
On June 8.1 UT, (~ three months after
discovery), we used LIRIS on the WHT
to obtain a 24-second exposure through
the J filter of the SN 2004ao field and
a ZJ spectrum (range 0.89 –1.53 µm,
ℜ ~700) of the supernova.
SN 2004ao is quite a bright supernova.
The object was clearly detected in the
J-band image (Figure 1) at the date
of the run, three months after its
discovery. A magnitude of J ~16.6 was
derived from differential photometry
using three field stars. A plot of the
SN 2004ao spectrum (1200s exposure)
is also displayed in Figure 1. The
spectrum shows a set of broad emission
bands superimposed on a quite flat
continuum, indicating that the SN was
close to reaching the nebular phase
at the date of our observation. Special
attention should be paid to the P-Cygni
feature, with the absorption at
~1.043 µm, as well as to the emission
bands at λλ ~0.924, 1.130 and 1.191µm
(all these wavelengths are referred to
the host-galaxy rest frame, which
corresponds to z = 0.0056).
Currently, few NIR spectra of corecollapse SNe are found in the
literature. In particular, this fact is
more evident for Type Ib SNe at phases
older than ~one month after maximum
(that would be useful for comparison
with our spectrum of SN 2004ao). Thus,
as a first step of our study, we have
compared the LIRIS SN 2004ao
spectrum with the available spectra
of core-collapse SNe acquired at nearly
similar SN ages. We found that the
features detected in our spectrum
were also found in the spectra of the
peculiar Type Ic SN 1998bw at phase
~ +50 days (Patat et al., 2001). In
addition, all these features were also
detected in the spectra of the Type IIn
SN 1998S at phases ~ +60 and ~ +110
Figure 1. J-band image (left) and NIR spectrum (right) of SN 2004ao, obtained on 8
June, 2004 ( t ~ +90 days) with LIRIS on the WHT. The nucleus of the host galaxy
UGC 10862 is visible to the northwest of the supernova. The slit position has been
marked with a box enclosing the supernova. North is to the top and East is to the left.
On the spectrum, the main features referred in the text have been marked with a
vertical line.
days (Fassia et al., 2001) as well as in
those of the Type II SN 1987A at phase
~ +110 days (Meikle et al., 1989). In
all of these NIR spectra, the He I
λ 1.083 µm is identified as the main
contributor to the P-Cygni feature,
whereas the three emission bands at
λ λ ~0.924, 1.130 and 1.191 µm are
attributed, respectively, to O I λ 0.926,
O I λ 1.129 + S I λ 1.131 + Na I λ 1.138
and Mg I λ 1.183 + Si II λ 1.205 µm.
From the absorption minimum of the
He I line, we derived an expansion
velocity of ~11,000 km s-1 for the ejecta
of SN 2004ao. Note that this value is
similar to the velocity values derived
in other “normal” Type Ib/c SNe (e.g.,
SN 1990W) from their NIR HeI lines
(Wheeler et al., 1994), significantly
lower than the velocity derived in
“peculiar” hyper-energetic core-collapse
SNe (eg., v ~13,000 –18,000 km s-1 in
SN 1998bw; Patat et al. 2001). From
the spectral data, we suggest that this
supernova probably was a “normal”
(i.e., non hyper-energetic) Type Ib SN,
despite it being a fairly bright object.
The SN 2004ao data recorded in
this observing test show the feasibility
to undertake programmes of
spectrophotometric follow-up of SNe in
the NIR window with LIRIS.
We thank all of the LIRIS Team for
the acquisition of SN 2004ao spectrum
and images during guaranteed time. ¤
Acosta-Pulido, J. A., Ballesteros, E., Barreto,
M., et al., 2002, ING Newsl, 6, 22.
Acosta-Pulido, J. A., Ballesteros, E., Barreto,
M., et al., 2003, ING Newsl, 7, 15.
Fassia, A., Meikle, W. P. S., Chugai, N., et
al., 2001, MNRAS, 325, 907.
Hamuy, M. , Maza, J., Pinto, P. A., et al.,
2002, AJ, 124, 417.
Jeffery, D., Branch, D., Filippenko, A.,
Nomoto, K., 1991, ApJL, 377, 89.
Matheson, T., Filippenko, A. V., Li, W.,
Leonard, D. C., Schields, J. C., 2001,
AJ, 121, 1648.
Matheson, T., Challis, P., Kirshner, R., 2004,
IAU Circ, 8304.
Meikle, W. P. S., Allen, D. A., Spyromilo,
J., Varani, G. F., 1989, MNRAS, 238, 193.
Patat, F., Cappellaro, E., Danziger, J. et al.,
2001, ApJ, 555, 900.
Singer, D., Li, W., 2004, IAU Circ, 8299.
Wheeler, J. C., Swartz, D. A., Harkness,
R. P., 1993, Phys Rep, 227, 113.
Wheeler, J. C., Harkness, R. P., Clocchiatti,
S., et al., 1994, ApJL, 436, 135.
Gabriel Gómez ([email protected])
No. 9, March 2005
LIRIS Discovers Supernovae in Starburst Galaxies
S. Mattila (Stockholm Observatory), R. Greimel (ING), P. Meikle (Imperial College, London)
n the nuclear regions of M82 and
other nearby starburst galaxies
one core-collapse supernova
(CCSN) is expected to explode every
5–10 years. Furthermore, in luminous
infrared galaxies (LIRGs) such as the
interacting system Arp299 (NGC3690
+ IC0694) at least one CCSN can be
expected every year. However, due to
the high dust extinction astronomers
have been unable to detect these SNe.
By observing in the near-IR Ks-band
the extinction is strongly reduced,
making searches for such dust obscured
SNe look feasible (Mattila & Meikle,
2001). In fact, recent near-IR searches
have been able to detect a couple of
SNe in starburst galaxies (Van Buren
et al., 1994; Maiolino et al., 2002).
These are however only extinguished
by a few of magnitudes in the visual
wavelengths (Mattila, Meikle &
Greimel, 2004). Now also the newly
commissioned near-IR imager LIRIS
on WHT has discovered two new
SNe within the nuclear regions of
Arp 299 and NGC 2146.
Already on the first run on 6 March
2004 LIRIS observed a SN, SN 2004am,
within the nuclear regions (~ 500 pc)
in one of our primary targets, M 82.
The discovery of this event, however,
had already been reported (Singer,
Pugh & Li, 2004) just one day before
our LIRIS observation. Our 0.89 –
1.53-micron LIRIS spectrum showed
broad (FWHM ~ 2800 km/s) hydrogen
lines demonstrating that this was a
type II event (Mattila et al., 2004). The
LIRIS JHKs images show a moderately
reddened source exactly coincident with
a bright starburst knot within the
nuclear regions of M 82. The opticalnear-IR colours also showed that the
extinction towards this SN was AV ~5.
In Figure 1, a JHKs image of M82
(+SN2004am) observed by LIRIS as a
part of our monitoring campaign on
2004 Nov 25 is shown together with a
subtracted Ks-band image clearly
showing the location of the SN. Note
that by this time the SN had already
dimmed considerably.
We have been carrying-out a near-IR
Ks-band search campaign for SNe
obscured by dust in the nuclear regions
of nearby starburst galaxies with the
William Herschel Telescope (WHT)
since August 2001. Initially, the search
started using the INGRID near-IR
imager (for details see Mattila et al.,
2002a). In March 2004 observations
with LIRIS commenced. By that time
the search had only produced the
detection of a possible SN (Mattila et
al., 2002b) in old images making any
follow-up observations and definite
confirmation of this SN impossible. We
estimated that the lack of SN
detections from the INGRID SN search
database indicates an average
extinction towards the nuclear SNe
exceeding AV =10 (see Mattila, Meikle
& Greimel, 2004). Such high
extinctions would certainly be expected
for most of the SNe within the nuclear
regions of starburst galaxies such as
M 82 (see Mattila & Meikle, 2001).
Our most recent LIRIS run on 2005
January 30 has, at last, produced
discoveries of subsequently confirmed
SN events in the interacting luminous
infrared galaxy Arp 299 (distance
~ 45 Mpc) and in the nearby starburst
galaxy NGC 2146 (distance ~ 13 Mpc).
Both Arp299 and NGC2146 have high
expected CCSN rates of ~1– 2 and
~ 0.2 SNe per year, respectively, as
indicated by their far-IR luminosities
(Mattila & Meikle, 2001). SN 2005U
(Mattila et al., 2005a), with m(Ks)=
16.2, was discovered at 3.7" west and
4.9" south of (or 1.3 kpc from) the Ksband nucleus A (Gehrz et al., 1983) of
Arp 299 (see Figure 2). A couple of days
later it was classified as a type II
within a few weeks past explosion
(Modjaz et al., 2005). The near-IR
colour of the SN estimated from our
LIRIS images, J –K = + 0.4 ± 0.5,
indicates an extinction of AV ~ 4
towards the SN. Another SN, SN
2005V (Mattila et al., 2005b), was also
discovered by LIRIS on the same night.
SN 2005V has a magnitude of m(Ks)=
Figure 1. Top: JHKs LIRIS image of M 82
(+ SN 2004am) observed on 2004 Nov
25. Bottom: The result of alignment,
image matching and subtraction (Alard,
2000) between LIRIS Ks band images
from March 2004 and November 2004.
Figure 2. JKs LIRIS image of Arp 299
(+SN 2005U) observed on 2005 Jan 30.
13.8, and is located at 1.8" east and
3.4" north of (or 330 pc from) the
Ks-band nucleus of NGC 2146
(Figure 3). On February 1, it was
spectroscopically classified as a type Ib/c
SN, about 1–2 weeks past maximum
light (Taubenberger & Pastorello, 2005).
The near-IR colours from LIRIS, J–H=
+0.13 ±0.33 and H–K = +0.18 ± 0.34,
indicate an extinction of AV ~ 3– 4
towards SN 2005V.
In Figure 4, a LIRIS Ks-band image
of the Antennae (NGC 4038/9) is
shown. This image obtained on 2005
January 30 shows also SN 2004gt
located within the circumnuclear
regions of the galaxy. The SN is clearly
No. 9, March 2005
visible in the subtracted image.
However, SN 2004gt had already been
discovered optically on 2004
December 12 (Monard, 2004), and
therefore is likely to have a modest
extinction. It has been spectroscopically
classified as a type Ib/c (Kinugasa et
al., 2004; Ganeshalingam et al., 2004).
Our combined INGRID and LIRIS SN
search database now includes repeat
images for 40 nearby starburst
galaxies, on average ~ 4.3 epochs per
target. However, the nuclear SN
detection efficiency falls rapidly as
the seeing quality declines. Therefore,
the depth of the search varies strongly
between the images with different
seeings. During the search there have
been four confirmed CCSN events
Figure 3. JHKs LIRIS image of NGC 2146 (+SN 2005V) observed on 2005 Jan 30.
Figure 4. Left: Ks band INGRID image of the Antennae (NGC 4038/9) observed on 2002 January 3 with ~ 0.8" seeing. Middle: Ks
band LIRIS image of Antennae (+SN 2004gt) observed on 2005 January 30 with ~1.6" seeing. Right: The result of alignment,
image matching and subtraction between INGRID and LIRIS images using the Optimal Image Subtraction method (Alard, 2000).
discovered in our starburst galaxy
sample, two of which were discovered
by us. In addition, we have a number
of unconfirmed possible SNe present
in our Ks-band data. All these were
detected in old images, and therefore
no optical/near-IR follow-up was
possible. Although, several CCSNe
have now been discovered in starburst
galaxies at near-IR wavelengths, they
are all extinguished by only a few
magnitudes in AV. The expected
population of highly extinguished
supernovae within the nuclear regions
of starburst galaxies therefore still
remains unrevealed. The final
conclusion from our study will require
extensive statistical analysis of the
near-IR SN search database. This is
now underway (Mattila et al., in prep.).
The WHT ‘Nuclear SN search’
nSN.html) team also includes Stuart
Ryder, Nic Walton, and Bob Joseph.
We thank Chris Gerardy, Per
Gröningsson, and Rubina Kotak for
taking part in some of the observing
runs. ¤
Mattila, S., Greimel, R., Meikle, W. P. S.,
et al., 2002a, ING Newsl, 6, 6.
Mattila, S., et al., 2002b, IAU Circ, 7865.
Mattila, S., et al., 2004, IAU Circ, 8299.
Mattila, S., Meikle, W. P. S., Greimel R.,
2004, New Astron Rev, 48, 595.
Mattila, S., Greimel, R., Gerardy, C., Meikle,
W. P. S., 2005a, IAU Circ, 8473.
Alard, C., 2000, A&AS, 144, 363.
Mattila, S., Greimel, R., Gerardy, C., Meikle,
W. P. S., 2005b, IAU Circ, 8474.
Ganeshalingam, M., Swift, B. J., Filippenko,
A. V., 2004, IAU Circ, 8456.
Modjaz, M., Kirshner, R., Challis, P., 2005,
IAU Circ, 8475.
Gehrz, R. D., Sramek, R. A., Weedman, D.
W., 1983, ApJ, 267, 551.
Monard, L. A. G., 2004, IAU Circ, 8454.
Kinugasa, K., Kawakita, H., Yamaoka, H.,
2004, IAU Circ, 8456.
Taubenberger, S., Pastorello, A., 2005,
IAU Circ, 8474.
Maiolino, R., Vanzi, L., Mannucci, F., et al.,
2002, A&A, 389, 84.
Mattila, S., Meikle, W. P. S., 2001, MNRAS,
324, 325.
Singer, D., Pugh, H., Li, W., 2004, IAU Circ, 8297.
Van Buren, D., Jarrett, T., Terebey S., et
al., 1994, IAU Circ, 5960.
Seppo Mattila ([email protected])
No. 9, March 2005
Addressing the Question Posed by the Of ?p Stars: HD191612
D. J. Lennon (ING), I. D. Howarth (UCL), A. Herrero (IAC), N. R. Walborn (STScI)
here are three known Of ?p
stars in our galaxy, they are the
well known peculiar stars
HD108, HD148937 and HD191612.
The question mark in their spectral
classification was introduced by
Walborn (1972) to indicate doubt that
these stars are normal Of supergiants.
They are characterised by their CIII λλ
4647, 4650, 4651 emission lines being
comparable in strength to their NIII
λλ 4634, 4640, 4642 emission lines,
unlike normal Of supergiants where
the CIII lines are always much weaker
(Figure 1). In addition the ultra-violet
spectra of Of?p stars also exhibit a
stellar wind morphology more akin to
O-type giants than to Of supergiants.
HD108 has been extensively studied
(Nazé et al., 2001) and is subject to
large and so far unexplained
spectroscopic variations, though with
a variability timescale of approximately
56 years systematic study is difficult.
HD148937 on the other hand, though
relatively little studied does exhibit an
impressive nitrogen rich ejection
nebula, NGC6164 and NGC6165
(Figure 2). Apparently HD148937
has undergone a previous catastrophic
mass loosing event, perhaps similar
to those of Luminous Blue Variables
such as P Cygni and Eta Carinae.
Therefore, despite their rarity, the
Of?p stars are well worth detailed
study as they may represent an
important phase in the short, and
spectacular, career of a massive star
approaching the end of its lifetime.
HD191612 came to our attention when
N. R. Walborn noticed that the
spectrum discussed by Herrero et al.
(1992) was different from the discovery
spectrum of Walborn (1973). This
realisation prompted a thorough check
of the historical publication record and
the ING archive at Cambridge, as well
as a drive to obtain new spectra
through ING’s service programme. As
a result the spectrum was found to be
highly variable, appearing to switch
between an O6 – 7 spectral type with
the Of?p characteristics and an O8
Figure 1. Montage of green region spectral data for HD191612. The June 1st 1993
spectrum of HD191612 was taken during its O6 like Of?p phase and illustrates a
typical characteristic of these peculiar stars, namely the CIII λλ 4647, 4650, 4651 lines
are comparable in strength to the NIII λλ 4634, 4640, 4642 lines. Note also the strong
emission present in HeII λ 4686. Compare with December 2002.
Figure 2. The ejection nebulae NGC 6164 and NGC 6165 surrounding the Of?p
star HD148937. This image is courtesy of Mischa Schirmer (ING) from Note the point-symmetric nature of the nebulae
around the central star.
No. 9, March 2005
spectral type in which the CIII emission
lines are absent (Figure1). While the
data precluded determining any
periodic behaviour of the spectrum,
Walborn et al. (2003, Paper I)
suggested that spectroscopic states
might persist for a decade, although
one transition occurred on a time scale
of only 13 months.
We continued to monitor HD191612
through 2003 and the first half of 2004
using the Isaac Newton and William
Herschel Telescopes, as well as several
other northern hemisphere telescopes;
WIYN, OMM, MMT, OHP, Skinakas,
and Loiano. While Paper I had left
HD191612 in its O8 state at the end
of 2002, May 2003 saw a return to the
O6 state, where it remained until a
possible transition in December of that
year. After a gap of five months the
star was recovered in its O8 state
implying that stable spectral states
last approximately 7– 9 months.
However an important breakthrough
came with the discovery of a periodic
behaviour of HD191612 in the
Hipparcos photometric survey (Nazé,
2004), with a period of approximately
540±13 days. Combining this with the
spectroscopic variability enabled us to
refine this period to 538±3 days which
is also consistent with Walborn’s initial
classification in 1973. Indeed all of the
data from Paper I, plus data from the
2003/04 campaign, perfectly match
this period, with the hotter O6 phase
occurring during maximum brightness,
accompanied by strong Hα emission
and reduced HeI line strengths. This
led us to predict that a transition
should occur in October 2004 (Walborn
et al., 2004, and Figure 3), a prediction
subsequently confirmed by our on-going
multi-site spectroscopic monitoring
campaign which by now had expanded
to include the NOT and TNG on La
Palma. The blue points in Figure 3
show the onset of transition occurring
as predicted with the very smooth
change in Hα as it switches from
absorption to emission, accompanied
by a weakening of the HeI lines.
Despite the wealth of observational
data now accumulated for HD191612,
this star, like the others in its class,
remains enigmatic. Its characteristics
cannot be explained by known
Figure.3 Illustration of spectral and photometric variability of HD191612. The upper
panel shows how the Hα line switches from absorption (positive equivalent width) to
emission (negative equivalent width). Note the good agreement between the data
points covering 22 years, or 16 cycles. The central panel highlights the change in
spectral type between the star’s O8 type (large He I equivalent width) to its O6 type
(small He I equivalent width). The bottom panel shows the light curve obtained from
the Hipparcos data.
mechanisms linked to rotation or
pulsation. Perhaps the most tempting
explanation lies in the regime of
binary evolution; a compact companion
in an eccentric orbit and small
periastron separation is one possible
model. Unfortunately, while we can
rule out radial velocity variations of
HD191612 greater than 10 – 20 km/s
this is not a strong constraint for this
scenario, improved observations around
a supposed periastron (Hα maximum)
are clearly desirable and ongoing.
The relatively short period of
HD191612 and wealth of spectroscopic
material make it an ideal candidate
for detailed study. In the coming year
we will continue to monitor HD191612
and look forward to complementing
the optical coverage with the
acquisition of X-ray data using XMMNewton (P. I. Nazé). The expectation
is that we will obtain X-ray spectra
at three phases representing typical
O6, O8 and transition states of this
star, along with contemporaneous
optical spectroscopy.
We would like to thank the many
observers and telescope groups who
took part in this campaign (see
Papers I and II), including Chris
benn, Roy Østensen and Gloria
Andreuzzi on La Palma. ¤
Herrero, A., Kudritzki, R. P., Vílchez, J.
M., Kunze, D., Butler, K., Haser, S.,
1992, A&A, 261, 209.
Nazé, Y., Vreux, J.-M., Rauw, G., 2001,
A&A, 417, 667.
Nazé, Y., 2004, PhD thesis, Univ. Liege.
Walborn, N. R., 1972, AJ, 77, 312.
Walborn, N. R., 1973, AJ, 78, 1067.
Walborn, N. R., Howarth, I. D., Herrero,
A., Lennon, D. J., 2003, ApJ, 588, 1025,
(Paper I).
Walborn, N. R., Howarth, I. D., Rauw, G.,
Lennon, D. J., Bond, H., Negueruela, I.,
Naze, Y., Corcoran, M., Herrero, A.,
Pellerin, A., 2004, ApJ, 617, L61,
(Paper II).
Danny Lennon ([email protected])
No. 9, March 2005
The Search for the Companion Star of Tycho Brahe’s
1572 Supernova
J. Méndez (University of Barcelona and ING)
n recent years, type Ia supernovae
(SNe Ia) have been used
successfully as cosmological probes
of the Universe (Riess et al., 1998;
Perlmutter et al., 1999). However, the
nature of their progenitors has
remained somewhat of a mystery. It
is widely accepted that they represent
the disruption of a degenerate object,
but there are also numerous progenitor
models (see for instance Ruiz-Lapuente,
Canal, Isern, 1997a, for a review), but
most of these have serious theoretical/
observational problems or do not
appear to produce sufficient numbers
to explain the observed frequency of
SNe Ia in our Galaxy (~ 3 ×10–3 yr –1;
Cappellaro & Turatto, 1997).
The Thermonuclear
Hoyle and Fowler (1960) described how
a white dwarf, a common end-point in
the evolution of low- and intermediatemass stars, could become a powerful
fusion bomb if its interior temperature
rose from about 2×108 to 5×108 K. They
anticipated that this type of explosion
could well correspond to the class of
objects identified by Minkowski (1941),
called supernovae of type I and much
later renamed type Ia. These
supernovae are characterised by their
spectral signatures and are the
brightest observable stellar explosions.
But, how can such high temperatures
(>108 K) be attained in the usually
cold degenerate cores of white dwarfs?
A natural way to heat white dwarfs up
is by the accretion of material from a
stellar companion. If the white dwarf
grows in mass by taking material from
a donor star, its central density and
temperature rise, and it can achieve
the critical condition near 1.4 solar
masses, the so-called Chandrasekhar
mass. The binary path is found to be
the easiest physical way to give rise
to bare white dwarfs exploding in large
enough numbers to account for those
supernovae. The single-star models
were both physically and statistically
unsuccessful. Recently, new momentum
has been given to the study of possible
evolutionary paths to explosion.
Observational efforts with specific
goals have been set up to clarify the
issue by contrasting the models with
empirical evidence.
Progenitor Models of
Type Ia SNe
The progenitor models can roughly be
divided into three classes: doubledegenerate (DD) models, subChandrasekhar models and singledegenerate (SD) Chandrasekhar
The DD alternative involves the
progressive approach of two white
dwarfs orbiting around the centre of
mass of the system while they emit
gravitational wave radiation (the
material accreted by the white dwarf
is neither H nor He but C+O from a
disrupted CO white-dwarf companion)
(Iben & Tutukov, 1984; Webbink,
1984). The less massive white dwarf
is disrupted in the process, forming a
torus of material around the most
massive one. The accretion of this mass
by the surviving white dwarf could
cause its explosion if the combined mass
is in excess of the Chandrasekhar mass
(∼ 1.4 solar masses). The lack of
detection of any surviving companion
could eventually confirm that it is
destroyed in the course of the binary
evolution, as expected in the merging
of CO white dwarfs. Some objections
have been raised, however: fine tuning
in the accretion process might be
required to avoid the burning of C into
Ne and Mg, which would lead to a
collapse event (i.e. undergoes
accretion-induced collapse; AIC) instead
of an thermonuclear explosion. There
may be a small parameter range where
AIC can be avoided, but it is unlikely
to account for more than a small
number of SNe Ia. This model
nevertheless has the advantage of
being in good agreement with the SN
rate in our Galaxy (Nelemans et al.,
A sub-Chandrasekhar-mass white
dwarf could produce a SN Ia if helium
is ignited violently in a shell
surrounding the CO core and
triggered a detonation wave that
propagates inward and ignites the CO
core (Woosley & Weaver, 1994; Livne
& Arnett, 1995). Although they might
not respond to the common type Ia
phenomenon, they could correspond
to very dim ones. A mixture of almost
standard Chandrasekhar explosions
with some very faint “peculiar” subChandrasekhar explosions could exist.
A few extremely faint type Ia
explosions have been identified, in
any case: The last supernova of type Ia
that exploded in the Andromeda
galaxy, in 1885, was of such a type.
On the other hand, the evolutionary
path toward explosion will not be
directly reflected in the spectrum of
the exploded white dwarf itself.
The arguably most favoured class of
models at the present time involves
single-degenerate scenarios, where the
white dwarf accretes from a nondegenerate companion star (Whelan
& Iben, 1973; Nomoto, 1982). In these
models, the companion star can be a
giant, a subgiant, a He star, or a
main-sequence star, ie. it may either
be a hydrogen-rich star or a helium
star. One of the major problems with
these models is that it is generally
difficult to increase the mass of a white
dwarf by accretion due to the
occurrence of nova explosions and/or
helium flashes (Nomoto, 1982) which
may eject most of the accreted mass.
There is a narrow parameter range
where a white dwarf can accrete
hydrogen-rich material and burn it in
a stable manner. Burning of the
accreted H into He and of the He into
C can lead to the growth in mass and
increase of the central temperature of
the star, which would finally explode.
Low accretion rates favours a much
less violent explosion: A nova, which
differs from a supernova in that the
white dwarf remains intact, and there
is opportunity for further recurrent
outbursts. Whereas a nova is a skindepth explosion, a type Ia supernova
affects the whole star. A number of
tests have been undertaken to reveal
whether such a picture involving a Hor He-donor companion is correct
(Ruiz-Lapuente, 1997b).
One promising channel that has been
identified in recent years relates them
to supersoft X-ray sources (Li & van
den Heuvel, 1997). In this channel, the
companion star is a somewhat evolved
main-sequence star or subgiant of
2 – 3 solar masses, transferring mass
on a thermal timescale to a white
dwarf. As an example, calculations
made by Podsiadlowski (2003) show
that an initial system consisting of a
2.1 solar masses somewhat evolved
main-sequence star and a 0.8 solar
masses white dwarf can make the
white dwarf grows very effectively.
When it reaches the Chandrasekhar
mass, it has parameters very similar
to U Scorpii, a supersoft binary and
recurrent nova where the white dwarf
is already close to the Chandrasekhar
mass and therefore one of the best
SN Ia progenitors currently known
(Thoroughgood et al., 2001).
While U Scorpii provides an excellent
candidate for a SN Ia, consistent with
theoretical expectations, it would be
even better to have a more direct
observational test for progenitor models
(Ruiz-Lapuente, 1997b), in particular
since it is quite possible, perhaps even
likely, that there is more than one
channel that leads to a SN Ia. Such
direct tests could involve the detection
of hydrogen or helium in the ejecta or
the supernova environment, which
could come from the outer layers of the
exploding object, circumstellar material
that was ejected from the progenitor
system (e.g. Cumming et al., 1996), or
matter that was stripped from the
No. 9, March 2005
Figure 1. Chandra image of Tycho SNR.
The colours in the Chandra X-Ray image
of the hot bubble show different X-ray
energies, with red, green, and blue
representing low, medium, and high
energies, respectively. (The image is cut
off at the bottom because the southernmost
region of the remnant fell outside the field
of view of the Chandra camera). The
bright star in the centre of the remnant is
the same bright star in the centre of
Figure 2 (star labelled ‘Tycho A’). Credit:
Chandra X-Ray Observatory/ DSS2.
secondary by the supernova interaction
and was mixed into the ejecta. A
particularly conclusive test would be
the detection of a companion star that
has survived the supernova explosion
in the supernova remnant. At present
the detection of a surviving companion
would only be feasible in our Galaxy.
The supernova of the millennium, the
Lupus supernova (also designated SN
1006 after the year of its appearance)
was a supernova of this type. The
supernova discovered by Tycho Brahe,
SN 1572, was also of this type. Both
are the only unambiguous type Ia
supernovae observed in our Galaxy
during the last thousand years.
Observable Consequences
on the Companion Star
The predictions of how the companion
star would look after the impact of the
supernova ejecta, if there is any
companion, were investigated by Canal,
Méndez and Ruiz-Lapuente (2001),
depending on the type of star it actually
is. Among other features, the surviving
companion star should have a peculiar
velocity with respect to the average
motion of the other stars at the same
location in the Galaxy — mainly due
to disruption of the binary— detectable
through proper-motion and radial
velocity measurements, and perhaps
also signs of the impact of the
supernova ejecta. The latter can be
twofold. First, mass should have been
stripped from the companion and
thermal energy injected into it, possibly
leading to the expansion of the stellar
envelope that would make the star
have a lower surface gravity. Second,
depending on the interaction with the
ejected material, the surface of the star
could be contaminated by the slowestmoving ejecta made of Fe and Ni
isotopes. If the companion’s stellar
envelope is radiative, such a
contamination could be detectable
through abundance measurements.
The Search for the
Companion Star of SN 1572
Tycho Brahe’s supernova (SN 1572) is
one of the only two supernovae
observed in our Galaxy that are
thought to have been of type Ia as
revealed by the light curve (RuizLapuente, 2004), radio emission
(Baldwin et al., 1957) and X-ray spectra
(Hughes et al., 1995).
The field that contained Tycho’s
supernova, relatively devoid of
background stars, is favourable for
searching for any surviving companion.
With a Galactic latitude b = +1.4°,
Tycho’s supernova lies 59–78 pc above
the Galactic plane. The stars in that
direction show a consistent pattern of
radial velocities with a mean value of
– 30 km s–1 at 3 kpc. The star most
likely to have been the mass donor of
SN 1572 has to show a multiple
coincidence: being at the distance of
SN 1572, showing an unusual motion
in comparison to the stars at the same
location, having stellar parameters
consistent with being struck by the
supernova explosion and lying near
the remnant centre.
The distance to SN 1572 inferred from
the expansion of the radio shell and by
other methods lies around 3 kpc. Such
a distance, and the light-curve shape
No. 9, March 2005
Figure 2 (left). B-band image of the centre of Tycho SNR from the Auxiliary Port camera at the William Herschel Telescope. The
emptiness of the field is remarkable. We carried out repeated photometric and spectroscopic observations of the included stars
in the surveyed area (see solid circle in Figure 3) at various epochs to check for variability and exclude binarity.
Figure 3 (right). Positions and proper motions of stars. Positions are compared with three centres: the Chandra (Ch) and ROSAT
(RO) geometrical centres of the X-ray emission, and that of the radio emission (Ra). Dashed lines indicate circles of 0.5 arcmin
around those centres and the solid line is a circle with a radius of 0.65 arcmin around the Chandra centre. The supernova position
reconstructed from Tycho Brahe’s measurements (Ty) is also shown, though merely for its historical interest. The proper motions
of the stars measured from HST WFPC2 images are represented by arrows, their lengths indicating the total displacements from
1572 to 2004. Error bars are shown by parallel segments. Red circles are the extrapolated positions of the stars back to 1572.
of SN 1572, are consistent with it being
a normal type Ia supernova in
luminosity, like those commonly found
in cosmological searches (RuizLapuente, 2004).
Given the age of Tycho SNR and the
lower limit to its distance (2.83 ±0.79
kpc), any possible companion, even if
it moved at a speed of 300 km s–1, could
not be farther than 0.15 arcmin from
its position at the time of the explosion.
However, the search radius
significantly expands owing to the
uncertainty in the derived centre of
the SNR. The radius of the remnant
is 4.325±0.025 arcmin (Ruiz-Lapuente,
2004) and the SNR is quite spherically
symmetric (see Figure 1). Nevertheless,
there is a 0.56 arcmin displacement
along the east-west axis between the
radio emission and the high-energy
continuum in the 4.5–5.8 keV band
observed by XMM-Newton in the
position of the western rim. Such
asymmetry amounts to a 14% offset
along the east–west axis. Evidence that
the ejecta encountered a dense H-cloud
at the eastern edge giving rise to
brighter emission and lower ejecta
velocity, while finding a lower-density
medium in the western rim, might
account for the asymmetry
(Decourchelle et al., 2001). In SNRs
from core-collapse supernovae (type
II), up to a 15% discrepancy between
the location of the compact object and
the geometric centre is found in the
most symmetric cases.
On the basis of the above considerations
we decided to cover 15% of the
innermost radius (0.65 arcmin) centred
on RA=00 25 19.9, Dec=64 08 18.2
(J2000), the Chandra Observatory
coordinates for the geometrical centre
of the X-ray emission of the SNR
(Figures 2 and 3). And as deep as V =22
so sampling main-sequence with
spectral types earlier than K6 (for
later types the total mass available
for transfer excludes them as viable
candidates to type Ia SN companions),
subgiant and red giant candidates at
the distance of the remnant (Canal,
Méndez, Ruiz-Lapuente, 2001). For a
description of our survey strategy see
Ruiz-Lapuente et al. (2003a).
We obtained spectra of most of the
stars in the surveyed area using Keck I,
NOT+ALFOSC, and photometric data
using the INT+PFC, WFC and
WHT+Aux Port Camera. All but one
of the observed stars are either mainsequence stars (luminosity class V)
with spectral types A4-K3 or giant
stars (luminosity class III) with spectral
types G0 – K3.
Red-giant stars are possible companions
of type Ia supernovae. Masses in the
range 0.9-1.5 solar masses are the
most favourable cases (Hachisu et al.,
1996). Red-giants have envelopes
loosely bound gravitationally, and upon
collision with the SN ejecta it should
be either completely stripped or just a
small fraction of it remains bound to the
core. In the former case, the remaining
No. 9, March 2005
He core would appear as a hot He
pre-white dwarf, not as a red giant. In
the latter case, the H-burning shell
would remain active and the residual
envelope would expand to red-giant
size. None of the detected red-giant
stars lie in one of these possibilities
and they are all at distances
incompatible with that of SN 1572.
Main-sequence stars are also viable
companions of type Ia supernovae.
Close binaries with 2 to 3.5 solar
masses main-sequence or subgiant
companions have indeed been
suggested as one class of systems able
to produce type Ia supernovae (Li et
al., 1997). Among systems containing
a main-sequence star, recurrent novae
have been pointed out as possible
progenitors (Livio & Truran, 1992).
Stripping of mass from the impact of
the ejecta on this type of companion
is also expected and as a consequence
the companion star increases its
volume and luminosity, to later return
to the equilibrium values of a star with
the new (decreased) mass (Canal et
al., 2001; Marietta et al., 2000;
Podsiadlowski, 2003). Main-sequence
companions should experience the
highest increase in peculiar velocity
(peculiar velocities up to 200 to 300
km s –1 after the explosion) as the
orbital separation of the binary system
is shorter than in other possible
progenitor models. However, the
detected main-sequence stars in the
sample have low peculiar velocities,
the surface abundances are compatible
with solar values and no odd
combinations of log g and Teff are found.
The Case of Tycho G
Tycho G is a subgiant G2IV star
located at 0.49 arcmin from the
Chandra centre of Tycho SNR. From
low resolution spectroscopy, and after
dereddening by E(B–V)=0.60±0.05 mag,
we derive a temperature of Teff =5750 K,
a surface gravity log g =4.0–3.0, and
solar metallicity from high-resolution
spectroscopy. For the spectral type
found and being a slightly evolved star
(surface gravity not much below the
main-sequence value), the mass should
be about solar and thus the radius, for
the range of surface gravities above,
Figure 4. Radial velocity in the Local Standard of Rest (LSR), versus distance for the
subsample of stars closer than 6.5 kpc. The dashed line shows the approximate
relationship for the stars in the direction of Tycho given by the expression vr =–vsolar
cos(l – lsolar)+A r sin(2l ), where l and lsolar are the respective Galactic longitudes of
Tycho SNR and the solar apex, vsolar is the Sun’s velocity in the LSR, A is the Oort’s
constant and r is the distance in kpc. We include two field stars (stars Tycho O and U)
that are slightly away from the search area but at distances in the range 2–4 kpc.
should be R ≈ 1– 3 solar radii, which
translates via our photometric data
(Tycho G’s apparent V magnitude is
18.71 ±0.04) into a distance d ≈2.5 –
4.0 kpc.
Tycho G could have been a mainsequence star or a subgiant before the
explosion. Main-sequence stars no
longer look like ordinary main-sequence
stars after the explosion of the
supernova, but subgiants with
envelopes expanded. Subgiants remain
subgiants of lower surface gravity
(Marietta et al., 2000; Podsiadlowski,
Stars at distances d ≈2.0– 4.0 kpc in
the direction of Tycho SNR move at
average radial velocity vr ≈ –20 to
–40 km s –1 (in the Local Standard of
Rest) with a ∼20 km s –1 velocity
dispersion (Binney & Merrifield, 1998;
Dehnen & Binney, 1998). Tycho G
moves at –108 ±6 km s –1 (heliocentric)
in the radial direction. In contrast, all
other stars with distances compatible
with that of SN 1572 have radial
velocitites within the velocity
dispersion as compared with the
average of all stars at the same location
in the Galaxy (see Figure 4).
From detailed proper motion
measurements on Hubble Space
Telescope WFPC2 images (RuizLapuente et al., 2003b) it is found that
Tycho G has tangential velocitites
µb = – 6.11 ±1.34 mas yr –1 and µ l=
– 2.60 ±1.34 mas yr –1 resulting in a
total tangential velocity of 94 ± 27
km s–1 (a 24 km s–1 systematic error
was added due to uncertainty in the
reference frame solution of the images).
This proper motion programme
continues in HST Cycle 13 where
measurements with smaller error bars
will be obtained using both WFPC2
and ACS. The other stars of our sample
do not show such coincidence in
distance and high tangential velocity.
Putting together radial and tangential
velocities, we derive a value of
136 km s–1 for the modulus of the
velocity vector of Tycho G, being a
factor of 3 larger than the mean
velocity value at 3 kpc.
This derived velocity lies in the range
of expected peculiar velocities of the
companion star from the disruption of
a white dwarf plus subgiant/ mainsequence system. The system would
have resembled the recurrent nova U
Scorpii, ie. a system made of a white
dwarf close to the Chandrasekhar mass
No. 9, March 2005
Figure 5. Model fits to observed spectra of the subgiant star Tycho G, the red giant star Tycho A and the main-sequence star Tycho
B. Identification of the most significant metal lines are given. We have not detected significant spectroscopic anomalies, either here
or in the whole sample, and most spectra are well reproduced assuming solar abundances. Thin lines correspond to the
observations and thicker lines to the synthetic spectra. Spectra were obtained at the WHT with UES and ISIS. Tycho A (bottom panel)
is the closest red giant in the sample. It is a K0 III star, and its mas should be 3 solar masses approximately. Tycho A is ruled out
as the companion star of SN 1572 on the basis of its short distance: 1.1± 0.3 kpc. All the other red giants are located well beyond
Tycho´s remnant, and therefore are also ruled out. The A8/A9 star Tycho B (second panel from bottom) has 1.5 solar masses,
which would fall within the appropriate range for main-sequence type Ia supernova companions, as it would have been massive
enough to transfer the required amount of mass to the white dwarf. The entirely normal atmospheric parameters, however,
strongly argue against any such event in the star’s recent past. The second and third spectra from the top show computed spectra
compared with observed spectra for Tycho G. The upper panel shows the observed spectrum near Hα. This line is blueshifted,
implying a peculiar radial velocity exceeding about 3 times the velocity dispersion for its stellar type.
(initial mass of the white dwarf 0.8
solar masses) plus a companion of
roughly a solar mass (initial mass of
the evolved companion 2.0 –2.5 solar
masses filling its Roche lobe) at the
moment of the explosion. The excess
velocity corresponds to a period of
about 2 –7 days (a period of 6 days
correspond to an orbital velocity of
90 km s–1 approximately). The effective
radius of the Roche lobe of the
companion just before the explosion
would have been 7 solar radii.Given the
effective temperature and luminosity
of Tycho G, the radius is less than 3
times the solar radius. This smaller
radius would be a consequence of mass
stripping and shock heating by the
supernova impact, plus subsequent
fast cooling of the outer layers up to
the present time.
the spectral fits [M/H ]>–0.5, however,
excludes this possibility (see Figures
5 and 6). Spectra taken at five different
epochs also exclude Tycho G is a singlelined spectroscopic binary.
Such a high velocity, however, could be
explained if Tycho G belongs to the
Galactic halo population. The lower
limit to the metallicity obtained from
Our search for the binary companion
of Tycho’s supernova has excluded
giant stars. It has also shown the
absence of blue or highly luminous
No. 9, March 2005
objects as post-explosion companion
stars. One of the stars, Tycho G of our
sample, show a high peculiar velocity
(both radial and tangential velocities),
lies within the distance range for the
explosion of SN 1572, and its type,
G2IV, fits the post-explosion profile of
a type Ia supernova companion whose
position in the Hertzsprung-Russell
diagram is untypical for a standard
If Tycho G is the companion star of
SN 1572, its overall characteristics
imply that the supernova explosion
affected the companion mainly through
the kinematics. Therefore, a star very
similar to the our Sun but of a slightly
more evolved type would have been the
mass donor that triggered the explosion
of type Ia SN 1572, connecting the
supernova explosion to the family of
cataclysmic variables.
The results of this research, led by
Pilar Ruiz-Lapuente of the University
of Barcelona, was published in the
October 28 issue of Nature. The coauthors are Fernando Comeron (ESO),
Javier Méndez (University of Barcelona
and ING), Ramón Canal (University
of Barcelona), Stephen Smartt (IoA,
Cambridge), Alex Filippenko
(University of California, Berkeley),
Robert Kurucz (Harvard-Smithsonian
Centre for Astrophysics), Ryan
Chornock and Ryan Foley (University
of California, Berkeley), Vallery
Stanishev (Stockholm University), and
Rodrigo Ibata (Observatory of
Strasbourg). ¤
Baldwin, J. E. et al., 1957, Observatory,
77, 139.
Figure 6. Left: A low-resolution spectrum over a wide wavelength range was obtained
with LRIS at the Keck Observatory (second from top) and it is compared with template
model spectra of the same spectral class and various metallicities. Right: Several fits
to Fe and Ni lines in Tycho G for solar abundances (bold line), [Fe/H]= –0.5 (dashed
line) and [Fe/H]= –1 (dotted line). The high content of nickel and iron in the gas of
Tycho G clearly identifies it as a star born in the Galactic Plane. The data was
obtained with ISIS at the WHT.
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54, 335.
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“Search for the Companions of Galactic
SNe Ia”, From Twilight to Highlight: The
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Riess, A., et al., 1998, AJ, 116, 1009.
Ruiz-Lapuente, P., Canal, R., Isern, J.,
1997a, “Thermonuclear Supernovae”,
NATO ASI Series C: Mathematical and
Ruiz-Lapuente, P., 2003b, “Probing the
nature of Type Ia SNe through HST
astrometry”, HST proposal 9729.
Ruiz-Lapuente, P., 2004, ApJ, 612, 357.
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423, 371.
Javier Méndez ([email protected])
No. 9, March 2005
PlanetPol: A High Sensitivity Polarimetre for the Direct
Detection and Characterisation of Scattered Light from
Extra-solar Planets
J. Hough1, P. Lucas1, J. Bailey2, E. Hirst1, M. Tamura3, D. Harrison1
1: University of Hertfordshire; 2: Macquarie University, Australia; 3: NAO, Japan.
fter commissioning on the
University of Hawaii 88-inch
telescope, PlanetPol has been
used successfully on the WHT in April
and October 2004. The instrument,
funded by PPARC, was designed and
built at the University of Hertfordshire.
PlanetPol is a stellar polarimetre
designed to measure fractional
polarisations of 10– 6 or less. With this
sensitivity PlanetPol should be capable
of detecting the polarisation signature
of so-called hot-Jupiters. These are
extra-solar planets (EXP) whose
size is approximately that of Jupiter
but with orbits that are 0.1AU or less
(orbital periods of a few days). The
linear polarisation should vary with
phase angle from zero at full phase to
a maximum whose amplitude and
position depends on the nature of the
scattering particles in the planetary
atmosphere. Measuring the
polarisation signature not only gives
a direct detection of the EXP, in
contrast to the more usual indirect
detections by which most EXPs are
discovered, but can provide information
about the planet’s albedo and radius,
and on the nature of the scatterers.
Further, from the position angle of
polarisation the inclination of the
planet’s orbit (i ) can be determined
thereby enabling the planet’s mass to
be determined. In contrast, techniques
such as the RV method only measure
M sin i .
Polarimetry is a technique that is
capable of very high sensitivity as it is
a differential technique that in
principle is not affected by the Earth’s
atmosphere, and hence is limited only
by photon noise. However, fractional
polarisations of a few parts in a million
are lower than most astronomical
polarimetres can achieve, although
comparable sensitivities have been
obtained before, albeit under somewhat
idealised conditions. Kemp et al. (1987,
Nature, 326, 270) measured the
integrated light from the sun and gave
an upper limit for the fractional
linear polarisation of 2×10 – 7. However,
Kemp et al. used a polarimetre that
directly viewed the sun, rather than
using an intermediate telescope, and
hence avoided the potential problem
of telescope polarisation.
PlanetPol has a classical design and
takes advantage of some of the
techniques pioneered by Kemp. It was
designed for use on a range of
telescopes, mounted at the unfolded
Cassegrain so as to minimise telescope
All high sensitivity polarisation
measurements to date have made use
of photoelastic modulators (PEM) in
which a slab of non-birefringent
material is stressed using a piezo at
the resonant frequency of the slab, f 0,
thereby reducing the power needed to
sustain a standing wave in the PEM.
Such devices are ideal as polarisation
modulators as they operate at
frequencies of tens of kHz, well above
seeing or scintillation fluctuations
produced by turbulence in the Earth’s
atmosphere and they do not involve any
rotating parts and so do not produce
any periodic motion of the image on
the detector, nor any periodic light
Figure 1. Top: Picture shows PlanetPol
on the WHT, with left to right: Edwin
Hirst, Phil Lucas, Jim Hough, Dave
Harrison and Jeremy Bailey. Bottom:
PlanetPol instrument.
modulation produced by dust on the
modulator. The PEMs in PlanetPol are
type I/FS20 made from fused silica,
with a PEM90 Controller, all
manufactured by Hinds Instruments.
A 3-wedge Wollaston is used as the
analyser, giving better image quality
than the more usual 2-wedge device.
Following the analyser are wheels with
colour filters and neutral density filters.
Two-element Fabry lenses image the
primary mirror onto single element
detectors, sufficient for a stellar
polarimetre, and these also eliminate
any problems with flat-fielding. The
very high modulation rates of the PEMs
(20kHz for PlanetPol) are, in any case,
incompatible with the readout rates for
CCDs, although the solar ZIMPOL
Polarimetre, see
noao/staff/keller/ uses the charge
shifting and storage capabilities of
CCDs to act as a synchronous
demodulator, thus largely overcoming
the readout limitations.
PlanetPol uses Avalanche Photodiodes
(APD), which have higher quantum
efficiency than photocathodes and
less noise than the external amplifier
of a photodiode, providing the best
signal to noise for the photon rates
achieved with PlanetPol. The APDs
were specially designed by Hamamatsu
(type C4777-SPL-S2383-70K),
operating with a gain of 100, a spectral
response covering 400 – 1000 nm, a
frequency response of 0–70 kHz (3dB)
and employ a 2-stage thermoelectric
cooler (TEC), giving a detector
temperature of – 20°C. They have a
nominal size of 1 mm with an
active area of 0.70 mm. Their NEP
is < 2f WHz –½.
PlanetPol has 2 channels, the star
channel, on the telescope axis, and a
sky channel, offset by 95mm. As only
one PEM is used in each channel, the
instrument has to be rotated through
45 degrees to measure the second
Stokes parameter for linear
polarisation. The analyser, together
with the filters, and detector
assemblies, can be rotated through
90 degrees so as to change the phase
of the modulated signal by 180 degrees,
and hence eliminate any offsets in
the signal detection train.
Each of 4 signal channels uses a
Stanford Research SR830DSP lock-in
amplifier to extract the linear
polarisation signal modulated at 40 kHz
(twice the modulation frequency of the
PEM). The DC signal from the
detectors is fed to a 16-bit ADC. An
ARCOM Industrial PC, running
Agilent Vee Pro 6 is used to control all
the mechanical functions of the
instrument, the settings of the lock-in
amplifiers and ADCs, and also acquires
and displays the data. Communication
with the ARCOM computer is via an
Adderlink KVM Extender, using a
dedicated ethernet line to a remote
monitor and keyboard in the
observatory’s control room. Data
reduction is carried out using a laptop
running IDL, which shares files with
the ARCOM over the LAN.
No. 9, March 2005
Figure 2. Schematic
of PlanetPol.
Figure 3. U and Q
polarisations for
nearby stars at
different parallactic
angles. U and Q
are not shown in
the equatorial
coordinate system.
polarisations are
in units of 10 –6.
In order to measure fractional
polarisations of 10– 6 or less, it is
essential to determine the telescope
polarisation (TP) so that the absolute
error in TP is much lower than 10– 6.
This was achieved by observing nearby
stars (typically within ~20pc) with the
telescope de-rotator on, causing the TP
to rotate while any other contributions
to the polarisation are fixed. Measuring
the polarisation of these nearby stars
as a function of parallactic angle should
produce, in the absence of any intrinsic
stellar polarisation, interstellar
polarisation, and instrument
polarisation, a sinusoidal curve in U
and in Q with an amplitude equal to
the telescope polarisation, and phase
shifted by 45°. Figure 3 shows the
measured U and Q polarisations as a
function of parallactic angle. In
practice, even for very nearby stars,
there will be some interstellar
polarisation and a curve was fitted to
the data set taking this into account.
The best fit curves give a fractional
polarisation for the TP of
(16.45 ± 0.20)×10 –6. This very low TP
makes the WHT an ideal telescope for
making very high sensitivity
polarisation measurements.
In the two observing runs to date
observations were made of τ Boo and
υ And, although poor weather has
meant that we have only limited data.
Nonetheless, the very good performance
of PlanetPol gives us confidence that
we can determine the polarisation
signature of the hot-Jupiter EXPs.
There are also several other
observational programmes that will
be possible with PlanetPol, with its
very high sensitivity. Of course, very
high sensitivities require large
numbers of photons with a fractional
polarisation of 1×10 – 6, requiring
2×1012 detected photons.
Some possible programmes are:
– the distribution of dust in the local
– oblateness of rapidly rotating stars,
– star spots on active stars,
– debris discs around young main
sequence stars. ¤
James Hough ([email protected])
No. 9, March 2005
An Updated View of the Light Pollution at the Roque de
Los Muchachos Observatory
M. Pedani (Fundación Galileo Galilei)
The Sources of Light
Pollution at La Palma
The Observatorio del Roque de Los
Muchachos (ORM), located at La Palma
in the Canary Islands is actually the
largest European Observatory in the
northern hemisphere. The site benefits
from good sky transparency, high
fractions of clear (~ 70 %) and
photometric nights (~60%) and a mean
seeing of 0.76" (Muñoz-Tuñón et al.,
1997). An inversion layer in the
1300–1700 m height range, guarantees
(though with many exceptions in winter)
stable observing conditions during 3/4
of the year. About 85,000 people live
in La Palma, mainly concentrated in
8 small towns within 15 k m of the
ORM. Given the altitude of the ORM,
the line-of-sight over the sea has a
radius of ~180km, enough to intercept
the lighting of the major Canary island
Tenerife (800,000 people and 120 km
distant) whose coast is visible to the
naked eye on very clear nights.
Nevertheless, its contribution to the
sky brightness, as well as that of two
small islands, (El Hierro and La
Gomera, 29,000 people and 40 km
distant) is negligible. In many cases,
the presence of the so called “sea of
clouds” below the thermal inversion
layer, greatly reduces outdoor lighting,
especially during the coldest months.
The Canary Sky Law, introduced in
1992 (McNally, 1994) put strict limits
on the type of lamps which can be used
for outdoor lighting, on their power,
and on orientation with respect to the
ground and implied that, after local
midnight, most of the high-pressure
sodium (HPS) and mercury lamps
must be extinguished, as well as all the
discharge-tube illumination. In general,
low-pressure sodium (LPS) lamps
should be used except in the urban
areas where HPS lamps are admitted
and a non-negligible fraction of mercury
and incandescent lamps still exist.
LPS lamps are the best choice for
astronomy because their emission is
almost exclusively concentrated in the
NaD λλ 5890–6 doublet, which simply
adds to the natural sky glow at these
wavelength. No continuum emission
arises from these lamps. Other
emission lines are Na I λλ 5683–8 and
Na I λλ 6154 – 61, the latter about 4
times weaker than the former.
Detecting the above lines in the sky
spectra permits the contributions to the
NaD 5890 – 6 emission from light
pollution and the natural sky glow to
be disentangled. Up to now, the only
way to measure the natural NaD
skyglow at ORM was during an
artificial 1 hour blackout on the night
24–25 June 1995 to celebrate the 10th
anniversary of the inauguration of the
ORM (see Benn & Ellison, 1998 for
The HPS lamps are the second
contributor in terms of light output on
La Palma. Their emission is
characterised by a smooth continuum
in the ~ 5500 to 7000 Å range. The
NaD λλ 5890 – 6 line, is now replaced
by a deep void. Other narrow emission
lines are: NaI λλ 4665 – 9, NaI
λλ 4979 – 83, NaI λλ 5149 – 53, NaI
λλ 5683– 8 and NaI λλ 6154 – 61.
Mercury lamps, though they contribute
with a mere 9 % to the total luminous
flux of the island are another important
source of light-polluting lines, especially
in the violet/blue region of the
spectrum. There is also a weak
continuum emission in the 3200–7800 Å
range. The most important lines
observed in our spectra are: HgI λ 4046,
HgI λ 4358, HgI λ 5461, HgI λ 5769 and
HgI λ 5790.
Incandescent lamps are a significant
source of light pollution before
midnight, though their solely
continuum emission is not considered
in the present work. Nevertheless,
BE98 estimated their contribution to
zenith sky brightness at V-band to be
0.01 mag.
At La Palma, light pollution originates
from 17,166 street lamps (end of year
2000, 23 % more than reported in
BE98) emitting a total of 1.56 ×105
klumens before midnight, reduced to
1.0×105 klumens after that hour. If we
consider that about 50 % of the light
is emitted by the fixtures and the
ground reflectivity is assumed 10 %,
we calculate that the amount of power
emitted upward by the outdoor lighting
is ~ 16 W/km2 before midnight and
~11W/km2 after. It is noteworthy that
the typical sky background of
V = 21.9 mag/arcsec 2 corresponds to
~ 9.2 W/km2.
Observational Data
Our sky spectra were obtained from
archival science frames taken in the
period August-December 2003 with
the 3.58 m Telescopio Nazionale
Galileo at La Palma using DoLoRes
(Device Optimised for Low Resolution),
equipped with a 2048 ×2048 pixel
thinned back-illuminated CCD with
15 µm pixels. Only spectra taken with
the LR-B Grism were considered, with
a final wavelength coverage of ~3800–
8000 Å. The slit widths used were 1.0"
and 1.3", yielding a resolution of
2.8 Å/pix and 3.6 Å/pix respectively.
Wavelength comparison lines were
obtained with a Helium lamp at the
beginning of each night. For the
present study, only deep exposures
taken with airmass < 1.3 during
photometric, moonless nights with low
extinction were selected. After a
careful visual inspection, those spectra
showing very similar content of light
pollution lines were aligned and coadded to build six template spectra
(hereinafter groups). These groups
span a wide range in azimuth, epoch
of the year and observing conditions,
crucial to disentangle environmental
and seasonal effects. As reported by
BE98, we also found noticeable nightto-night variations in the intensity of
the light pollution lines; this could be
due to the presence of clouds below
the ORM, blocking most of the outdoor
lighting. To reduce the errors on the
final line fluxes, we decided to include
in the same group only those spectra
whose NaD λ 5892 line fluxes differed
by no more than 30 %. In particular,
the spectra with the highest Na line
fluxes (less cloud cover) were
NaI Lines – Natural and
Artificial Contributions
Given the population of lamps at La
Palma, the Na I lines are by far the
most important sources of light
pollution at ORM. BE98 reported a
median equivalent width of NaD
λ 5892 of ~ 100 Å (~ 100 R, 1 R ≡ 1010/
/(4π) photons s–1 m–2 ster–1) during
summer, of which ~ 70 R due to outdoor
lighting and ~30 R due to the natural
skyglow. The natural NaD skyglow is
known to have a strong seasonal
variation, going from ~30 R in summer
to ~ 200 R in winter (Schubert &
Walterscheid, 2000). A noticeable effect
we found in our spectra is the
decrease of the Na and Hg lines in
the spectra taken after local midnight,
when most of the HPS and mercury
lamps are switched off, according to
the Canary Sky Law.
To disentangle the natural and
artificial contributions to the NaD
λλ 5892 – 6 emission we used our Group
5 and 6 spectra taken respectively
before and after midnight. Note that
no seasonal effect is present since both
of them were taken at the end of
September 2003. We assumed that all
the Na λλ 5683 – 8 flux of Group 6 is
due to LPS lamps while that of Group
5 is the sum of LPS and HPS
contributions. Thus the fractional
contribution of LPS to NaI λλ 5683–8
No. 9, March 2005
Group 2 Group 3 Group 4 Group 5 Group 6
Hg I λ 4046
Hg I λ 4358
N I λ 5199
Hg I λ 5461
O I λ 5577
Na I λ 5683 – 8
Hg I λ 5769
Hg I λ 5790
NaD λλ 5890– 6 189(156) 148(89) 658(431) 284(134) 251(162) 270(161)
Na I λλ 6154– 61
Table 1. Fluxes of the most important emission lines as measured in our spectra.
Values are in R (rayleigh, see BE98 for some useful conversion formulas). When not
detected, a line is labeled with “n.d.”; if the line was too noisy/faint or either blended
with another line, it is labeled with “n.a.”. Contribution to NaD λλ 5890– 6 from light
pollution is shown in parentheses.
emission of Group 5 is 3.6 /11.4 = 0.32
and that of HPS is 0.68. From the
Philips catalogue of lamps we derived
the ratio NaD λλ 5892– 6 /NaI
λλ5683–8=44.6 for the SOX LPS 35W
lamps mostly used at La Palma. For
Group 6 we calculate that light
pollution from LPS lamps contributes
~ 3.6 × 44.6 =161 R to the NaD
λλ 5890 – 6 flux; Group 5 has an
identical value since LPS lamps are
never switched off during the night. We
deduce that at the end of September
2003 the natural NaD λλ 5892 – 6
skyglow at ORM was ~ 90 –100 R .
We also tried another approach to
verify our assumptions about the
fluxes of Na I λλ5683 – 8 for Groups 5
and 6. The ratio of the illumination
contribution of HPS vs. LPS lighting
in La Palma is ~ 0.48. From the Philips
catalogue of lamps, as most of the HPS
lamps at La Palma are SON-T 70 W,
we calculate that the flux of NaI
λλ5683 – 8 emitted by a LPS lamp is
0.38 times that emitted by a HPS lamp.
Thus, for Na I λλ 5683 – 8 of Group 5
we obtain that 3.4 R are from LPS
lamps and 8.0 R are from HPS lamps.
These values are in very good
agreement with those obtained above
by simply assuming that all the flux
of NaI λλ5683 – 8 in Group 6 (3.6 R )
comes from LPS lamps.
Group 1 (see Figure 1) is our longest
exposure spectrum and well represents
the average observing conditions at
ORM after midnight when looking at
± 5 hrs from the meridian. The first
important difference from BE98 is that
we now clearly detect NaI λλ5683 – 8
emission, while Na I λλ6154 – 61 is still
undetected. Moreover, the Group 1
spectrum shows that the average
contribution of light pollution to the
NaD λλ 5892– 8 flux in the southern
regions of sky after midnight is
~ 150 R , about twice the value
measured in 1998.
Group 2 (see Figure 1) is interesting
because it was taken towards the NW,
a zone with relatively low light
pollution as confirmed by the lowest
contribution of artificial NaD λλ 5892– 8
detected in our spectra (89 R ). With
respect to Group 1, the higher flux of
NaI λλ5683– 8 is due to the fact that
Group 2 was taken before local
Group 3 has light pollution lines with
abnormally high fluxes (see Figure 1).
It was taken looking in the direction of
the most polluting towns of the island,
before midnight and with thin clouds
above the ORM (no data are available
for the atmospheric extinction). A direct
estimate with the above explained
procedure of the artificial contribution
to the NaD λλ 5892– 8 gives 431 R ,
which would result in a natural NaD
background of 227 R , somewhat higher
than expected at the end of October.
In this case, the presence of high clouds
could have played a role in reflecting
back light pollution to the observatory.
Group 4 is a typical spectrum taken
looking toward a moderately polluted
No. 9, March 2005
Figure 1. The night-sky spectra. The Group 1 (4 hrs total exposure) is the average of 8 spectra and best represents the average
observing conditions at ORM. The Group 2 spectrum was taken towards the NW, the least light-polluted zone at ORM. The
Group 3 spectrum was taken towards the most light-polluted region of sky at ORM, before midnight. The presence of thin clouds
could explain the abnormally high fluxes of the light polluting lines.
region of sky, ~ 2 hrs before meridian.
Here, the effects of the two urban
areas of Breña Alta/Breña Baja and
partly of Santa Cruz de La Palma are
evident. The higher-than-average
levels of the Na lines (note the NaI
λλ 5683 – 8 flux of 9.5 R ) are also due
to the fact that it was taken before
midnight. We estimate the contribution
of light pollution to the NaD λλ 5892– 8
to be 134 R .
The above discussed Group 5 and
Group 6 are typical spectra taken at
the meridian where the line of sight
intercepts the town of El Paso. The
decrease of the Na lines fluxes is
evident in Group 6, taken after
midnight. The contribution of light
pollution to the NaD λλ 5892– 8 is
~ 160 R, similar to that of Group 4 and
Group 1. In all our spectra, the fluxes
of the NaD λλ 5892 – 6 line are always
1.5 – 2.5 times higher than those of
BE98. In principle this indicates that
light pollution due to LPS and HPS
lamps considerably increased in the
last 5 years at La Palma, despite the
efforts made to control it.
Canary Sky Law; observations made
in the less polluted region of sky before
midnight imply higher fluxes of Hg
lines than those made toward a more
polluted region but after midnight.
HgI Lines
The most striking feature in our
spectra is the line detected in Group 3
(see Figure 1) at 5355.5 Å which we
identified as Sc I (tabulated λ is
5356.09 Å, see Table 6 of Slanger et
al., 2003). Sc is used as an additive to
high-pressure metal halide lamps.
Since on La Palma these are used only
in the soccer stadiums (to be
extinguished after 23:00), our detection
could have coincided with some
nocturnal sporting activity. The line at
5351.1 Å detected in Group 4 (see
Figure 2) can also be identified as ScI
emission (tabulated λ at 5349.71 Å).
The Group 3 shows other two lines
never detected before at ORM: HgI
λ 5769 and HgI λ 5790, only observed
If we consider Group 1, the emission
of the lines HgI λ 4358 and HgI λ 5461
is about half that reported in BE98
but our spectrum also shows the line
HgI λ 4046 detected for the first time
at ORM and with intensity comparable
to HgI λ 5461.
Although the Group2 spectrum was
taken in a less polluted region of sky,
it has ~ 40 % more Hg emission than
Group 1 and half the Hg emission of
Groups 4 and 5 taken toward two
towns before midnight. This
demonstrates the benefits of the
No. 9, March 2005
Figure 2. The night-sky spectra. The Group 4 spectrum was taken toward a moderately polluted region before midnight. The Group
5 spectrum was taken toward the meridian before midnight. The Group 6 spectrum was taken toward the meridian after midnight.
at Mount Hamilton (Slanger et al.,
2003) and Kitt Peak (Massey et al.,
1990). Though very faint, these lines
also appear in our Groups 5 and 6, with
a clear dimming after midnight evident
in the latter spectrum.
To conclude, the average fluxes of the
Hg lines detected in our spectra are
~ 50% fainter than those reported in
BE98. When observing toward a town,
the Hg lines have about the same
intensities as in 1998. Our directional
spectra show for the first time the
effect of the application of the Sky
Law after midnight but it is evident
that Hg lamps are never completely
extinguished after that hour, since
Hg lines are present in all our spectra.
For a typical town like El Paso (see
Groups 5 and 6), we infer that only half
of the mercury lamps are extinguished
after midnight. At La Palma, the
average intensity of the NaD λλ 5892– 8
line emitted by LPS lamps increased
by a factor of 1.5 – 2 over the last 5
years and its contribution to the sky
background is 0.05– 0.10 mag at V-band
and 0.07– 0.12 mag at R-band,
depending on the region of sky and the
time when observations are made. The
IAU’s recommendation that NaD
λλ 5892– 8 emission should not exceed
in intensity the natural background, is
definitely no longer met. Na lines such
as NaI λλ 5683– 8 and NaI λλ 6154– 61
were also detected in our spectra for
the first time. Light pollution from Hg
lamps is ~ 50 % lower than in 1998,
except when observations are made
looking toward the towns, before
midnight; in this case we found very
similar levels. Though in non-optimal
atmospheric conditions, we detected
in Group 3 one strong line which was
identified as ScI. This element is used
as an additive in high-pressure metal
halide lamps which, to our knowledge,
are only used in the soccer stadiums
on La Palma. The presence of this
type of lamp on La Palma is confirmed
by another line at 5351.1 Å detected
in the Group 4 spectrum which can
also be identified as Sc I emission. ¤
Benn, C. R., Ellison, S. L., 1998, La Palma
Technical Note, 115. (BE98)
Massey, P., Gronwall, C., Pilachowsky, C.
A., 1990, PASP, 102, 1046.
McNally, D. (ed.), 1994, “The Vanishing
Universe – Adverse Environmental
Impacts on Astronomy”, Cambridge
University Press.
Muñoz-Tuñón, C., Vernin, J., Varela, A. M.,
1997, A&AS, 125, 183.
Schubert, G., Waltersheid, R. L., 2000, in
Allen’s Astrophysical Quantities, ed. A.
N. Cox (New York: AIP Press; Springer),
4th edition.
Slanger, T. G., Cosby, P. C., Osterbrock,
D. E. et al., 2003, PASP, 115, 869.
Marco Pedani ([email protected])
No. 9, March 2005
Joint ING and NOT Conference: Second Meeting on Hot Subdwarf
Stars and Related Objects
ogether with the Nordic Optical Telescope,
the ING is organising a meeting with the
title “Hot Subdwarf Stars and Related Objects”,
to be held on La Palma from the 6 to 10 of June
this summer. The conference venue is the Real
Club Náutico of Santa Cruz de La Palma, and it
will be the first major astronomy conference to be
held in the home town of the ING’s sea-level
Financial support has been given by the
organisers, the Excmo. Cabildo Insular de La
Palma (local government) and the Patronato de
Turismo de La Palma (tourist board).
Additionally the Real Club Náutico has been
extremely helpful by making their facilities
available to us at no cost.
This conference is the second meeting on hot
subdwarf stars, a new biennial series that was
started at Keele University in 2003. It is an
offspring of the long running White Dwarf
meetings, which counted their 14th meeting last
year. The intention is that the Subdwarf
meetings will also run every second year, in the
odd years between the WD meetings. The aim of
the workshop series is to disseminate recent
results on the properties, formation, and
evolution of the hot subdwarf stars and related
objects, and to assess the impact of these results
on other areas of astrophysics.
Hot subdwarf stars are extreme horizontal
branch (EHB) stars and pre-white dwarf stars.
The EHB stars are core helium-burning stars
with extremely thin hydrogen envelopes, and
form the majority of bright stars in surveys for
extremely blue objects, where they are classified
as subdwarf-B (sdB) stars. They also appear in
the colour-magnitude diagrams of some globular
clusters as an extension of the blue tail formed by
classical horizontal branch stars, though it is not
clear why some clusters show this feature and
others do not. The pre-white dwarf stars are
related to the sdBs, but have exhausted their
capacity to burn helium in the core. Many of the
brightest hot subdwarfs in the field are of this
class, and they are classified as sdO stars.
Topics for the meeting includes: Evolutionary
models and the UV-upturn phenomenon; hot
subdwarfs and hot HB stars in the field, clusters
and galaxies; hot subdwarfs in binary systems;
atmospheric properties of hot subdwarf stars;
asteroseismology of sdB stars, and progenitors
and progeny of sdB stars.
The capacity of the conferences is limited by the
size of the available facilities to about 90 people.
More information can be found on the ING webpages, at
subdwarf/. The registration is open until April 1. ¤
Roy H. Østensen on behalf of the Local Organising
Committe ([email protected])
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No. 9, March 2005
The Travelogue of an Astronomer*
S. Hameed (Astronomy Department, University of Massachusetts)
*: Article published in the Pakistan newspaper ‘Dawn’ on 17 October 2004.
oughly 3 million years back, a series of volcanic eruptions raised a huge mass of land to a height of over 3000 meters. The primary volcano lost its fight to
gravity and eventually collapsed 500,000 years ago to form a huge caldera. Today this is the most dominant feature on the island of La Palma in the
Spanish Canary Islands, located in the Atlantic Ocean off the coast of Morocco. The rim of the caldera is now populated with instruments designed to answer
some of humanity’s most profound questions about our place in the universe. Three million years of landscaping has provided astronomers an ideal place to
gaze at the heavens.
I was awarded 4 nights to use the 2.5 meter Isaac Newton Telescope, one of the ten telescopes located at La Palma. The size denotes the diameter of the main
mirror of the telescope; the bigger the mirror the more powerful is the telescope. The 10 meter Keck telescope is the largest in the world and is located in Hawaii.
My journey started from Amherst, Massachusetts. I packed my observing notebook in the backpack along with other travel essentials, and just like my passport
and my toothbrush, I was not going to let it separate from me at any cost. In order to get to La Palma, I had to fly first from Boston to Madrid, then from
Madrid to the island of Tenerife, and finally on a small propeller plane to La Palma. Observatories are usually located in such remote and exotic locations
because astronomers seek places that have little or no light pollution, are high-up on the mountain and are close to the ocean. The tall peaks of the mountains
provide the necessary dry conditions and the ocean smooths the air that, as a result, improves the quality of the pictures taken through the telescope. Thus,
volcanic islands, like La Palma and Hawaii, are some of the world’s best locations for astronomy and provide astronomers an excuse to visit these visually
stunning places.
Before getting to La Palma, I spent a night in Tenerife. I was expecting Tenerife to be a small sleepy island geared solely for entertaining tourists from western
Europe. While tourism is indeed one of its main industries, Tenerife turned out to be a busy port with a population of over half a million. I stayed in a small
university town, La Laguna, located roughly 6 km from the capital city of Santa Cruz. It was in Santa Cruz I learnt that, despite its remote location, Tenerife
has played its role in history. The legendary British naval officer, Lord Nelson (1758-1805) or better known as Horatio Nelson, lost his arm in the battle for
Tenerife in 1797. The guilty cannon has been preserved and is now one of the tourist attractions on the island. Horatio Nelson survived the cannon shot, but
died at the hands of a French sniper in the battle of Trafalgar in 1805. I don’t know what happened to the rifle of the sniper, but the Trafalgar Square in London
can be seen as a memorial to the war achievements of Lord Nelson.
Tenerife also has a footnote in relatively recent Spanish history. General Franco, who was in exile on the island, flew from Tenerife to take control of Spanish
troops in Morocco, an event that started the bloody Spanish civil war in 1936, leading ultimately to the Fascist victory in 1939.
After staying overnight in Tenerife, I flew to La Palma on a small plane that braved the winds of the Atlantic ocean. Even though the flight lasted only 20
minutes, the turbulence made it seemed much longer. Perhaps this is the only occasion when I not only paid attention to the instructions given by the airhostess regarding life-jackets, but also read additional material on plane safety and escape routes. At La Palma airport I was relieved to see a smiling taxi
driver holding a sign of the telescope with my name on it.
La Palma is a small island with a population of roughly 80,000. This volcanic island is the youngest amongst the Canary Islands and is still geologically active.
I don’t think I felt completely reassured to know that the last major volcanic eruption on the island occurred in 1971. The landscape of the island is dominated
by the Caldera of Taburiente, formed by the collapse of the primary volcano. The rim of the caldera, roughly 10,000 feet above sea level, was my destination.
The road up the mountain had endless twists and turns and the landscape changed dramatically in the hour long drive from the airport to the observatory.
The sight and sound of waves crashing on the beach gave way to our passage through a forest of dense pine trees leading up to an almost barren top. Reflection
of sunlight from one of the telescope domes provided the first greeting from the observatory and the secrets of the night sky seemed safely hidden in the
stunningly beautiful dark-blue sky.
The taxi dropped me at the residential area for astronomers which is like a small hostel with a cafeteria. My telescope was located a few kilometres away but
I could see its dome from the window of my room. I was given keys to a car and my first afternoon was spent checking instruments at the telescope. Everything
was ready now. All I had to do was wait for the Sun to go down.
Meal times at observatories are dictated by the Sun. Dinner is usually served 2 hours before the sunset. Fish was on the menu for the first night. I got my plate
and looked for a table with English conversation; this is usually the table of astronomers. It is exciting to meet astronomers from all over the world and to learn
about their research. The astronomer sitting next to me had flown from England and was working on galaxies that formed when our universe was “only” a
billion years old. A Dutch astronomer was searching for exploding stars in nearby galaxies, while giant eruptions from stars was the interest of another. The
conversation at dinner ranged from the latest science results to politics and local culture. Now we were all ready to go to our respective telescopes.
After dinner I waited outside for the sky to get dark. My mind wandered off thinking about the indigenous people that lived here several centuries ago and
how they would have looked up and interpreted the sky. La Palma (and the other Canary Islands) were first settled by native Canarians, called Guanches,
whose origin is still controversial. Guanches are now extinct, but are thought to be an offshoot of the race of Berbers from northern Africa. The Spanish conquest
of the Canary Islands began in 1402 and went on until 1496. Despite having enormous technological advantage, the Spanish Conquistadors faced stiff
resistance from the natives, in particular from legendary Tanausú, who ruled the Kingdom of Aceró on the island of La Palma. Tanausú fought from the base
of the Caldera and was finally defeated with treachery in 1493. The sight of a majestic sunset brought me back to the present. Earth’s rotation was taking the
rays of the Sun away from the Earth. A layer of clouds could be seen covering the ocean below us. Like the eyes of a giant but curious beast, I could see the
slits of the neighbouring telescope domes open up.
I pointed my telescope first at a galaxy named NGC 210, the two hundred and tenth object in the New General Catalogue of galaxies. Apart from a few nearby
galaxies, most galaxies have numerical numbers assigned to them. Still, that does not take away the majesty of an individual galaxy containing roughly a
hundred billion stars. I am searching for new born stars in some of these galaxies. My journey to the Canary Islands took only two days from Massachusetts,
but the light photons hitting the mirror of the telescope, in the case of NGC 210, started their journey 60 million years ago. The light has taken so long to get
to us that some of the stars are probably already dead but we are just getting the news of their birth. After taking several images of NGC 210, I turned my
attention to NGC 660 followed by other galaxies.
The first night goes smoothly, and my work is interrupted only by the increasing brightness of the sky due to dawn. I close off the telescope dome and walk
outside to look at the caldera. Inside the caldera stands the monolith Idafe, an altar for the original indigenous people to worship their god Abora. I could not
help but wonder if, in our quest to understand our origins, the telescopes are the new altars for humanity. ¤
No. 9, March 2005
News from the Roque
t the time of writing, the 10-m GTC telescope, the flagship project at the Roque de Los Muchachos Observatory,
continues to make very good progress. As can be seen from the web cameras on the GTC’s web page
( the main telescope structure is essentially complete and many of the
mirror segments have already been received. The year 2005 will be an important one for the GTC project, as the telescope
will be prepared to receive the first photons.
The GTC project will also have a base at sea level in a brand new building, the Centro Astronómico de La Palma (CALP),
which is nearing completion at the time of writing. The GTC offices are located in Breña Baja, only a few kilometres from
the main town of Santa Cruz. We hope that the short distance between the Mayantigo building and CALP will help foster
close collaboration between the various observatory groups.
Left: Progress on GTC Telescope, picture grabbed from internal webcam on 25 February. Right: Picture of CALP base.
The Liverpool telescope has had its first robotic observations last year.
Following an upgrade to the hydraulic system for the enclosure, the telescope
will be fully ready for regular operation.
A long-standing item on the wish-list of the observatory has been the
construction of a visitor’s centre where the public can receive information about
the functioning of the observatory, amongst other things. The growth in tourism
and the resulting increase in numbers of visitors to the observatory has made
this even more important in recent years. Latest progress is that land a little
down-hill from the observatory has been made available for the construction of
a visitor’s centre. This important step may well mean that such a centre will
become reality not too long from now.
The fact that the Canary Islands are not always blessed with sunny skies is
indicated by the adjacent pictures, taken during one of the severe snowy periods
that this winter has produced. We’re contemplating adding skis to the standard
observatory outfit. ¤
René Rutten ([email protected])
Views of the snown observatory. From top to bottom: An ING´s car almost covered by snow (credit Juan Carlos Pérez); View of
Fuente Nueva site from JKT´s internal live camera; Panoramic view from nitrogen plant (credit Jürg Rey).
No. 9, March 2005
WINT: Observing Time Awarded to High School Students
from The Netherlands
N. Douglas (Kapteyn Institute, University of Groningen)
s well as extending the borders of our knowledge of the universe, one of the
tasks of Astronomy is to communicate these efforts to the public and to
encourage the emergence of the next generation of astronomers. The Dutch graduate
school “NOVA” recently organised “WINT”, a competition amongst high school
students throughout the Netherlands. At stake for the forty or so contestants, from
which four winners had to be selected, was a trip to La Palma and share in two
nights of observing time with the Wide Field Camera at the 2.5m INT (the name of
the project means “winning” in Dutch, as well as being the acronym for “observing
time at the INT”).
The proposals were diverse, ranging from popular targets such as planetary nebulae
to challenging observations such as the smaller moons of Saturn and minor planets.
The main selection criteria were that the proposals should be well researched and
that the observing parameters had been checked, as well as that data would be
obtained which could be used for exercises in the classroom later.
The winners were Caroline Straatman who was interested in the stellar colours
arising from galaxy collisions, Max Verhagen who wanted to obtain images and
colours of the stars and nebulosity in the Pleiades, Evelien Dam who wanted to
recover the smaller moons of Saturn, and Suyan Zhang who wrote the best case for
Students at the INT control room during WINT
the Owl Nebula, a popular target. We also allocated secondary programs for each of
the school students, to be done if time allowed and, in the case of Evelien’s project,
to allow for the evident difficulty of her prime target. The winners were all (near) school leavers of age 16 –18. Accompanying them were
two students of Astronomy from the University of Groningen, Else Starkenburg and Jakob van Bethlehem, myself, and a science
reporter. Prof Peter Barthel and Jacques Visser provided organisation and logistical support in the Netherlands.
The prize included a guided tour of the island, visits to some of the observatory facilities, and observing on February 24 and 25. By
chance, the first night coincided with an occultation of a star by a minor planet, the narrow footprint of which passed through the Canary
Islands ! A webcam was set up to allow the “folks back home” to follow the action and to contribute suggestions via an interactive forum.
The weather on arrival at La Palma was poor, and this hindered the sightseeing trip somewhat, the the extent of the problem only
becoming apparent when we were denied access to the mountain for the first night of observing (immediately ruling out the occultation).
This type of decision is not taken lightly, as was confirmed the next day when we drove up to the observatory in a convoy of (unusually
slow) taxis. We were confronted with scenes of chin-high snow dunes, heavy clearance machines, bitingly cold winds, and a generally
pessimistic feeling about the prospects of observing on this, our second and last night. ING, sensing this also, had started to open the
door to partial use of a third night.
In the end, and to everyone’s relief, we did in fact observe throughout the entire second night, despite the imminent danger of the wind
forcing the dome to close. Data was obtained for all projects and we were even able to put some preliminary results on the website, which
was designed by another student in Groningen, Christiaan Boersma. A victim of our own success, the webcam could not handle the
number of hits and failed at the moment supreme, but we continued to receive messages of support and excitement from home base.
The data is bound to keep a large number of Dutch school children busy in the coming weeks.
After a few hours sleep in the Residencia we learned that the weather had again taken a turn for the worse and were further impressed
when we spotted what appeared to be a royal decree referring to the danger of high winds. Due to fly back to the Netherlands early the
next day, we decided that risk of becoming stuck on the mountain was too much to ignore, despite the enticement of further observing.
Thus, we returned to sea level by way of a two-and-a-half hour taxi ride in poor conditions, only to hear rumours that many flights from
La Palma had been cancelled. I will spare the account of chaos at the overstretched airport at La Palma, but in the end we arrived back
in Amsterdam nearly two days later than planned. The first newspaper articles had begun appearing, and the WINT project, we learned,
would feature the coming weekend in a national newspaper, as well as in a radio program to be compiled from audio material gathered
by the reporter who had accompanied us on the trip.
Despite the weather-related setbacks and delays, our little group continued throughout to bask in the satisfaction of having visited the
observatory and having used the powerful Isaac Newton Telescope for a whole night, under circumstances which came very close to us
not even being able to leave sea level during the entire trip. We enjoyed each other’s company, and I was moved by the first new message
to appear on the website following our return, written by Max, one of the participants: “I miss La Palma already...” Truly, we did our
share to guarantee the emergence of the next generation of astronomers ! ¤
Nigel Douglas ([email protected])
No. 9, March 2005
Visits to ING
A total of 860 visitors split in 42 tours were shown round the WHT and occasionally the INT
from September 2004 to January 2005. In total 203 official tours were organised and 5656
visitors shown around in 2004, including Open Days. Visitors included the general secretary
of the Swedish Royal Academy of Sciences and Ireland’s embassador in Spain. The television
programme ‘Redes’ of Spanish TVE and the series ‘Schrödingers Katt’ of the Norwegian NRK
TV were filmed, and the programme series ‘Un Programa Estelar’ comprising six chapters
filmed in 2003 was shown on the Spanish TVE2 channel twice. From 8 to 14 November the
Spanish Education and Science Ministry and the IAC celebrated the European Science Week
on La Palma. As part of the activities, an excursion to the observatory was organised in
collaboration with the Public Outreach group of OPTICON (accompanying photos). ¤
Javier Méndez ([email protected])
Amateur Awards
n 2004 two people working or collaborating with ING were awarded with
important amateur distinctions. Mischa Schirmer, ING support astronomer, was
awarded a special mention (telescope category) for his photographs of NGC 2246,
M33 and NGC 7023 at the first national astrophotography competition
“Fotocósmica 2004”organised by the IAC. All the awarded photographs were taken
at sea level a bit south of Santa Cruz de La Palma. The telescope was a 20 cm f /3.8
(760 mm focal length) Flat Field Camera (“FFC”) from Lichtenknecker Optics. More
information on the individual photographs can be found at
Nik Szymanek, an amateur astronomer in the United Kingdom who collaborates
with ING in public outreach activities (see, for instance, ING Newsl., 6, 29), was the
2004 recipient of the Astronomical Society of the Pacific’s Amateur Achievement
Award. Given annually since 1979, the Amateur Achievement Award is designed to
recognise significant contributions to astronomy or amateur astronomy by those not
employed in the field of astronomy in a professional capacity. The Society’s Board
of Directors noted Szymanek’s leadership in state-of-the-art imaging and image
processing — especially his true-colour, deep-sky images produced from the data
obtained by observers at ING— and his ongoing contributions to education and
public outreach. ¤
Seminars Given at ING
Visiting observers are politely invited to give a
seminar at ING. Talks usually take place in the
sea level office in the afternoon and last for about
30 minutes plus time for questions afterwards.
Astronomers from ING and other institutions on
site are invited to assist. Please contact Danny
Lennon at [email protected] and visit this URL:
seminars.html, for more details. These were
the seminars to 1st of March:
Feb 18. Hugo Schwarz (CTIO/NOAO/AURA),
“The SOAR telescope is nigh ! ”.
Dec 1. Santi Cassisi (Osservatorio Astronomico di
Collurania in Teramo), “Hot Stellar
Populations in Galactic Globular Clusters: The
population(s) puzzle goes deeper”.
Nov 22. Sonia Fornasier (Astronomy Dep. of
Padova University), “Physical Studies of Minor
Aug 10. Angelo Antonelli (INAF-Osservatorio
Astronomico di Roma, Italy), “Gamma Ray
Bursts in the SWIFT Era”.
Javier Méndez ([email protected])
Left: Awarded photograph of NGC 2246, the Rosette Nebula by Mischa Schirmer. The image was obtained through an Hα filter
on a 2×2 mosaic of 21 images totalising an exposure time of 3 hours and 30 minutes. Right: Picture of the WHT taken by Nik
Szymanek with a digital camera.
Danny Lennon (Head of Astronomy, ING)
We have also commissioned the new
ISIS TV slit viewing camera, discussed
in the article by Simon Tulloch in
ING Newsletter, 8, 20. This camera is
based on a Peltier cooled frame transfer
CCD, and can be controlled in much
the same way as any other CCD at the
ING. Besides offering better image
quality and improved ease of
acquisition for ISIS it offers the
additional advantage that one can now
take an acquisition image of the slit
during a science exposure. Finally
during the coming year we expect to
see the image slicer commissioned on
ISIS, this will have a 2 arcsec entrance
aperture and a 0.5 arcsec sliced output
image, nicely matched to the optimum
resolution of the ISIS CCDs.
The digital media storage landscape
continues to change very rapidly, which
is just as well given the increasing rate
Applying for Time
ver the years the instrument
suite at the WHT has changed
many times. One constant in
all these changes is that our
intermediate dispersion spectrograph
ISIS continues to win the largest share
of the observing time across all our
three TACs. It’s therefore good to see
some improvements coming to this
venerable instrument. The past 6
months have seen the commissioning
of a new dichroic beam splitter, and
initial tests indicate that the infamous
ripples which plagued the old dichroic
set are substantially reduced.
Throughput in both blue and red arms
is improved, while the response of the
new blue fold mirror is also
substantially better than before (details
may be found on the ISIS web pages).
This is the only dichroic which will be
offered in service mode, and will be
the default dichroic offered to visiting
observers unless an alternative is
specified. It is expected that the older
dichroics will be phased out of use
pending feedback from users.
No. 9, March 2005
of data acquisition in astronomy. A
number of survey programmes using
the WFC on the INT have highlighted
this issue recently due to their
extremely high data rates (and short
exposure times), and the ING now has
a provision to allow users to copy their
data to external firewire discs. If users
can demonstrate a clear need for this
facility on the INT and wish to
avail themselves of the service they
should contact Robert Greimel
([email protected]).
Despite some minor teething problems
during 2004B, LIRIS continues to
perform very well at Cassegrain. We
will therefore continue with our policy
of only offering LIRIS for use at this
focal station for IR imaging (and
spectroscopy), INGRID will continue
to be used with NAOMI, our natural
guide star AO system. OASIS is
performing as expected, however it
should be noted that with OASIS there
is the choice of using the instrument
with or without AO correction.
Furthermore, during 2005A, we expect
to finish commissioning a mode of
operation in which only tip-tilt
correction is applied, somewhat relaxing
the constraint on the magnitude of
the guide star while still providing
attractive performance in the I-band.
The Director’s Message has already
referred to the questionnaire which has
been released by ING in order to gauge
the views of the astronomical
community on the future of the
observatory. While individual responses
are confidential, the overall results will
be fed into the ING review process later
this year and will have an influence
on the future development of ING and
its instrumentation suite. For example,
the default situation on the future for
the WHT is essentially the continuation
of the existing suite of instruments,
which now comprises optical and IR
imaging and spectroscopic capability,
15 March, 15 September
15 March, 15 September
(31 March for 2005B)
1 April, 1 October
A: 1 February – 31 July
B: 1 August – 31 January
multi-object spectroscopy, and adaptive
optics (AO) at optical and IR
wavelengths. Our ongoing development
currently focuses on extending the use
of the AO suite through the use of a
Rayleigh laser beacon which will
dramatically increase the sky coverage
and hence the scientific potential of
the existing AO system. The INT is
currently a single instrument telescope,
utilising the Wide Field Camera, and
no change in this status is as yet
decided upon. It is very important
therefore that our users complete and
submit the questionnaire if they wish
to have their say on the future of ING.
Danny Lennon ([email protected])
No. 9, March 2005
Telescope Time Awards Semester 2005A
The principal investigator, institution or university, title of
the programme, and programme reference for every telescope
and allocation are listed below. Service programmes are not
included. For observing schedules please visit this web page:
– Tadhunter (Sheffield). Ultraluminous infrared galaxies:
quasars and radio galaxies in the making? W/2005A/1.
– Tanvir (Hertfordshire). The physics of short bursts and
relativistic blast waves. W/2004B/51 LT.
– Wilkinson (IoA, Cambridge). Dark matter at the edge of the
Sextans dwarf spheroidal. W/2005A/35.
ITP Programmes on the ING Telescopes
– Gänsicke (Warwick). Towards a global understanding of
close binary evolution. ITP7.
William Herschel Telescope
– Ahmad (Armagh Observatory). Parameters of hot
subdwarfs of the double-lined spectroscopic binary — PG
1544+488. W/2005A/46.
– Bailey (Anglo–Australian Observatory). A high precision
polarization survey of bright stars. W/2005A/10.
– Blundell (Oxford). A complete spatial and dynamical study
of the microquasar SS433. W/2005A/52.
– Bower (Durham). The Lyman-α haloes of SCUBA galaxies:
exploring super-winds and feedback at z=3. W/2005A/21.
– Christian (Queen’s University, Belfast). ISIS characterisation
of variable stars from the SuperWASP survey. W/2005A/36.
– Dobbie (Leicester). A rigorous examination of the
evolutionary status of SDSS hot DB white dwarfs within
the DO/DB gap. W/2005A/5.
– Gänsicke (Warwick). SW, Sextantis stars — totally normal?
– Hewett (IoA, Cambridge). Imaging of spectroscopically
selected gravitational lenses from the SDSS. W/2005A/19.
– Hough (Hertfordshire). Circular spectropolarimetry of
DIBs. W/2005A/7.
– Jarvis (Oxford). Spectroscopic redshifts for the first radio
galaxy sample selected at 74 MHz. W/2005A/8.
– Keenan (Queen’s University, Belfast). The space density of
B-type stars in the Galactic halo. W/2005A/6.
– Knigge (Southampton). Spectroscopic reconnaissance of
candidate emission line stars discovered by IPHAS.
– Kosroshah (Birmingham). A membership study of the
nearest fossil group. W/2005A/17.
– Kurosawa (Exeter). The clumpy nature of O supergiant
stellar winds. W/2005A/42.
– Levan (Leicester). Probing the high redshift universe with
GRBs. W/2005A/53.
– Lucas (Hertfordshire). PLANETPOL polarimetry of Tau
Boo Ab. W/2005A/20.
– Magrini (Firenze, Italy). The chemical content of nearby
galaxies: GR 8. W/2005A/29.
– Merrifield (School of Physics and Astronomy, Nottingham).
Determining the dynamics of round elliptical galaxies using
the Planetary Nebula Spectrograph. W/2005A/37.
– Pettini (IoA, Cambridge). The nature of DLA galaxies
traced through spin temperatures: the optical survey.
– Pozzo (ICL). Late-time study of the very nearby Type IIP
SN 2004dj. W/2005A/13.
– Cappellari (Leiden Observatory). Dark matter in early-type
galaxies: stellar line-of-sight velocity-distribution at 5Re
using SAURON. w05an005.
– Douglas (Kapteyn Institute). Determining the dynamics of
round elliptical galaxies using the Planetary Nebula
Spectrograph (PN.S). w05an014.
– Franx (Leiden Observatory). Infrared spectroscopy of
restframe optically red galaxies at high redshift.
– Groot (Nijmegen). High-resolution eclipse mapping of
accretion disks in cataclysmic variables. w05an004.
– Helmi (Kapteyn Institute). Building up the Milky Way halo
via accretion of small satellites. w05an017.
– McDermid (Leiden Observatory). The central black hole in
NGC 4486A: measuring the mass and environment with
OASIS+NAOMI. w05an023.
– Roelofs (Nijmegen). Measuring directly the anticipated
tidal deformation of the accretion disk of AM CVn.
– Wijers (Astronomical Institute, Amsterdam). The physics of
short bursts and relativistics blast waves. w05an013.
– Wijers (Astronomical Institute, Amsterdam). Probing the
high redshift universe with GRBs. w05an020.
– Beckman (IAC). Basic properties of the nuclear bars in
galaxies with double bar. W39/2005A.
– Cairós (IAC). Near infrared mapping of blue compact dwarf
galaxies: disentangling the starburst and the old stars.
– Casares (IAC). Determining system parameters of a Soft Xray transient in outburst. W1/2005A.
– Eiroa (Autónoma de Madrid). IMF to the subestellar limit
in extremely young pre-main sequence clusters: Serpens.
– González (IAA). Finding an evolutionary link between radio
galaxies and very luminous infrared galaxies. W8/2005A.
– Gorgas (Complutense de Madrid). The star formation
history of elliptical galaxies in different environments.
– Licandro (IAC/ING). The Deep Impact experiment.
– López (IAC). Studying the dynamics and origin of nuclear
bars. W38/2005A.
– López-Martín (IAC). Identifying and characterising the
counterparts to ULXs. W30/2005A.
– López-Sánchez (IAC). Star formation zones in starburst
galaxies with tidal streams. W51/2005A.
– Mediavilla (IAC). Photometric and spectroscopic variability
of gravitational lenses. WL2/2005A.
– Mollá (CIEMAT, Madrid). Stellar populations in cooling
flow cluster galaxies. W22/2005A.
– Pérez (Autónoma de Madrid). Propagation of star formation
in apparently compact blue galaxies. W29/2005A.
– Rodríguez (Vigo). Physical parameters and chemical
abundances in hot type O subdwarfs. W26/2005A.
– Shahbaz (IAC). The origin of the optical variability in the
black hole X-ray transient V404 Cyg. W50/2005A.
– Zapatero (LAEFF-INTA). Brown dwarfs around poor
metallicity stars. W21/2005A.
– Zeilinger (Institute for Astronomy, Viena). Ram-pressure
stripping in Virgo cluster galaxies and their extraplanar
ionised gas. W56/2005A.
Spanish Additional Time
– Balcells (IAC). GOYA deep infrared survey. W41/2005A.
– Hammersley (IAC). Visible spectroscopy of the GTC
standards. W31/2005A.
– Herrero (IAC). Detecting the population of blue massive
stars to 5 Mpc for OSIRIS. W40/2005A.
– Martín (IAC). A search for brown dwarf candidates in three
young open clusters for GTC follow-up. W3/2005A.
WHT-TNG Time Share
– Jeffers (Observatoire Midi-Pyrenees, France). Starspot
tracking on the W Ursae Majoris system 44 Boo.
W/2005A/24 [on the TNG].
– Quirrenbach (Leiden Observatory). Line bisector variations
for K giant stars with possible planetary companions.
w05an001 [on the TNG].
– Trevese (Roma). Investigating the nature of Low Luminosity
Active Galactic Nuclei (LLAGN). T15 [on the WHT].
Instrument Builders' Guaranteed Time
– Bacon (CRAL-Observatoire, Lyon). GT Type A.
– Bacon (CRAL-Observatoire, Lyon). GT Type B.
– Manchado (IAC). LIRIS GT.
Isaac Newton Telescope
– Burleigh (Leicester). Faint planetary nebulae around hot
white dwarfs. I/2005A/8.
– Coates (Mullard Space Science Laboratory). Wide-field
imaging of Comet 9P/Tempel during the Deep Impact
collision. I/2005A/11.
– Drew (ICL). IPHAS — the INT/WFC photometric Hα survey
of the northern galactic plane. I/2005A/7.
– James (Liverpool John Moores). Star formation history of
dwarf galaxies in the Virgo cluster. I/2005A/6.
– Jarvis (Oxford). A wide-field search for Lyman-α haloes: A
pre-requisite for massive galaxy formation? I/2005A/2.
– Mackey (IoA, Cambridge). A survey for dwarf galaxy
remnants around outer halo globular clusters. I/2005A/1.
– Ramsay (Mullard Space Science Laboratory). RApid Time
Survey - Exploring a new temporal parameter space.
No. 9, March 2005
– Zeilinger (Institute for Astronomy, Viena). Ages and
metallicities of dwarf ellipticals in clusters at z= 0.04.
– Aragon (Kapteyn Institute). Measuring galaxy spin
alignments along a void-intersection filament near AWM3.
– Franx (Leiden Observatory). Practical astronomy for 2nd
year students. i05an005.
– Groot (Nijmegen). IPHAS — the INT/WFC photometric Hα
survey of the northern galactic plane. i05an001.
– Kovac (Kapteyn Institute). The optical counterparts of the
smallest gas-rich galaxies. i05an006.
– Röttgering (Sterrewacht Leiden). Lyα emission line halos
and the properties of z >2 proto-clusters. i05an002.
– Beckman (IAC). The links between bars and star formation:
An advanced survey. I9/2005A.
– Castro-Tirado (IAA-CSIC). Physical characterisation of
Gamma-ray bursts (GRBs) in the SWIFT era. W25/2005A
– Deeg (IAC). Sample definition for exoplanet detection by
the COROT spacecraft. I11/2005A.
– Hatziminaoglou (IAC). Deep imaging in SWIRE ELAIS N1
and N2 fields. I1/2005A.
– Iglesias (Laboratoire d'Astrophysique de Marseille). The
impact of starbursts in the halos of dwarf galaxies.
– Leisy (IAC/ING). IPHAS — the INT/WFC photometric Hα
survey of the northern galactic plane. I3/2005A.
– López (IAC). The luminosity function of galaxies in
Hercules supercluster. I10/2005A.
– Martínez (Valencia). Dwarf galaxy population around
isolated galaxies and in small groups. I4/2005A.
– Martínez-Delgado (Max-Planck-Institut fur Astronomie,
Heidelberg). Two new ultra-faint Milky Way companions.
– Zurita (Granada). Global morphology of star formation:
Local calibration. I7/2005A.
Spanish Additional Time Allocations
– Rebolo (IAC/CSIC). Subestellar populations in young
clusters and stellar associations: I. Orion Belt and
Praesepe. I8/2005A.
– Vílchez (IAA). Deep Hα imaging of clusters of galaxies in
the WINGS Survey. I12/2005A.
Comité para la Asignación de Tiempo
International Time Programme
Long term
Netherlands Foundation for Research in Astronomy
The Netherlands
Panel for the Allocation of Telescope Time
Programme Committee
Time Allocation Committee
Telescopio Nazionale Galileo
The United Kingdom
Table of Contents
Message from the Director . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
The Isaac Newton Group of Telescopes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
The ING Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
The ING Director’s Advisory Group . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
The ING Newsletter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
“IPHAS: Surveying the North Galactic Plane in Hα”, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Final Data Products” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
J. A. CABALLERO, V. J. S. BÉJAR, “Direct Detection of Giant Exoplanets” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
G. GÓMEZ, R. LÓPEZ, J. ACOSTA-PULIDO, A. MANCHADO, “LIRIS Observations of SN 2004ao” . . . . . . . . . . . . . . . . . . . . . . . . . 14
S. MATTILA, R. GREIMEL, P. MEIKLE, “LIRIS Discovers Supernovae in Starburst Galaxies” . . . . . . . . . . . . . . . . . . . . . . . . . . 16
D. J. LENNON, I. D. HOWARTH, A. HERRERO, N. R. WALBORN, “Addressing the Question Posed by the
Of?p Stars: HD191612” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
J. MÉNDEZ, “The Search for the Companion Star of Tycho Brahe’s 1572 Supernova” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
J. HOUGH, P. LUCAS, J. BAILEY, E. HIRST, M. TAMURA, D. HARRISON, “PlanetPol: A High Sensitivity Polarimetre for the Direct
Detection and Characterisation of Scattered Light from Extra-solar Planets” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
M. PEDANI, “An Updated View of the Light Pollution at the Roque de los Muchachos Observatory” . . . . . . . . . . . . . . . . . . . 28
R. ØSTENSEN, “Joint ING and NOT Conference: Second Meeting on Hot Subdwarf Stars and Related Objects” . . . . . . . . . .
“Other ING Publications and Information Services” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
S. HAMEED, “The Travelogue of an Astronomer” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
R. RUTTEN, “News from the Roque” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
N. DOUGLAS, “WINT: Observing Time Awarded to High School Students from The Netherlands” . . . . . . . . . . . . . . . . . . . . .
J. MÉNDEZ, “Visits to ING” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
J. MÉNDEZ, “Amateur Awards” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
“Seminars Given at ING” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
D. LENNON, “Applying for Time” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
“Important” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
“Telescope Time Awards Semester 2005A” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Contacts at ING
ING Reception
Head of Administration
Head of Astronomy
Head of Engineering
Operations Manager
Telescope Scheduling
Service Programme
WHT Manager
INT Manager
Instrumentation Technical Contact
Health and Safety
Public Relations
René Rutten
Les Edwins
Danny Lennon
Gordon Talbot
Kevin Dee
Ian Skillen
Pierre Leisy
Chris Benn
Romano Corradi
Tom Gregory
Juan Martínez
Jürg Rey
Javier Méndez
Tel. (+34 922)
E - mail
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
Roque de Los Muchachos Observatory, La Palma
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