ISSN 1783-3426
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IAU GA Beijing: JD2, SpS5 and WG business meeting
Massive open star clusters using the
VVV survey I. Presentation of the data and description of the
approach
Two compact HII regions at
the remote outskirts of the Magellanic Clouds
Using
MOST to reveal the secrets of the mischievous Wolf-Rayet binary CV
Ser
Limb-Darkened Radiation-Driven
Winds from Massive Stars
Binary
interaction dominates the evolution of massive stars
On
the formation of CIII 4647-50-51 and CIII 5696 in O star
atmospheres
On the Weak-Wind
Problem in Massive Stars: X-ray Spectra Reveal a Massive Hot Wind in
mu Columbae
Post-doctoral position in stellar
astrophysics
2X Post-Doctoral
Positions Available in Theoretical Astrophysics
Annual
Meeting of the Astronomische Gesellschaft: The Bright and the Dark
Sides of the Universe.
30 Doradus:
The Starburst Next Door
Betelgeuse
Workshop 2012
Outstanding Problems
in Massive Star Research -- the final stages
Dear colleagues,
this
is just a brief note on important dates during the GA which are of
particular interest for our massive star community (i.e., for those
of you who will attend the GA). For further details, have a look into
the programme which can be downloaded from the IAU website
(wwww.iau.org)
1. JD2 on Very Massive Stars in the Local
Universe: Room 302 A+B
Monday 20th, 10:30 - 18:00
Tuesday
21st, 10:30 - 12:30
Wednesday 22nd, 10:30 - 15:30
2. SpS5
on the IR-view of massive stars: Room 303 A+B
Thursday, 23rd,
10.30 - 18:00
Friday, 24th, 8:30(!!!) - 15:30
3. Working
group business meeting
Wednesday 22nd, 16:00 - 18:00, Room
405
Everbody who is interested is cordially invited to our
business meeting: We intend to discuss the 'new' IAU structure, the
implications for our WG, the question whether to re-apply for turning
the WG into a commission, and the upcoming election of new OC members
just after the GA ...
... and any other business you might be
interested in!
With best regards, Jo Puls (Chair of
OC)
Weblink:
Email:
uh101aw@usm.uni-muenchen.de
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A.-N. Chené (AA), J.
Borissova (AB), J. R. A. Clarke (AC), C. Bonatto (AD), D. J. Majaess
(AE), C. Moni Bidin (AF), S. E. Sale (AG), F. Mauro (AH), R. Kurtev
(AI), G. Baume (AJ), C. Feinstein (AK), V. D. Ivanov (AL), D. Geisler
(AM), M. Catelan (AN), D. Minniti (AO), P. Lucas (AP), R. de Grijs
(AQ)
AA: U. de Concepción, U. de Valparaíso; AB: U. de
Valparaíso, The Milky Way Millennium Nucleus; AC: U. de Valparaíso,
U. of Hertfordshire; AD: U. Federal do Rio Grande do Sul; AE: Saint
Mary's University; AF: U. de Concepción; AG: U. de Valparaíso, PUC
de Chile; AH: U. de Concepción; AI: U. de Valparaíso; AJ: IALP; AK:
IALP; AL: ESO; AM: U. de Concepción; AN: The Milky Way Millennium
Nucleus, PUC de Chile; AO: The Milky Way Millennium Nucleus, PUC de
Chile, Vatican Observatory, Princeton University; AP: U. of
Hertfordshire; AQ: Kavli Institute for Astronomy and
Astrophysics
Context: The ESO Public Survey "VISTA
Variables in the Vía Láctea" (VVV) provides deep multi-epoch
infrared observations for an unprecedented 562 sq. degrees of the
Galactic bulge, and adjacent regions of the disk. Aims: The VVV
observations will foster the construction of a sample of Galactic
star clusters with reliable and homogeneously derived physical
parameters (e.g., age, distance, and mass, etc.). In this first paper
in a series, the methodology employed to establish cluster parameters
for the envisioned database are elaborated upon by analyzing a
subsample of 4 known young open clusters: Danks 1, Danks 2, RCW 79,
and DBS 132. The analysis offers a first glimpse of the information
that can be gleaned for the final cluster database from the VVV
observations. Methods: Wide-field, deep JHKs VVV observations,
combined with new infrared spectroscopy, are employed to constrain
fundamental parameters for a subset of clusters. Results: Results
inferred from the deep near-infrared photometry which features
mitigated uncertainties (e.g. the accuracy of the photometry is
better than 0.1mag for Ks<18mag), the wide field-of-view of the
VVV survey, and numerous high quality low resolution spectra
(typically more than 10 per cluster), are used to establish
independent cluster parameters which enable existing determinations
to be assessed. An anomalous reddening law in the direction toward
the Danks' clusters is found, i.e. E(J-H)/E(H-Ks)=2.20+/-0.06, which
exceeds published values for the inner Galaxy. The G305 star forming
complex, which includes the Danks' clusters, lies beyond the
Sagittarius-Carina spiral arm and occupies the Centaurus arm.
Finally, the first deep infrared color-magnitude diagram of RCW 79 is
presented which reveal a sizable pre-main sequence population. A list
of candidate variable stars in G305 region is reported.
Reference:
A&A, in press
Status: Manuscript has been
accepted
Weblink: http://arxiv.org/abs/1206.6104
Comments:
Email: andrenicolas.chene@gmail.com
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R. Selier, M.
Heydari-Malayeri
LERMA, Observatoire de Paris
The H
II regions LMC N191 and SMC N77 are among the outermost massive
star-forming regions in the Magellanic Clouds. So far, few works have
dealt with these objects despite their interesting characteristics.
We aim at studying various physical properties of these objects
regarding their morphology (in the optical and Spitzer IRAC
wavelengths), ionized gas emission, nebular chemical abundances,
exciting sources, stellar content, age, presence or absence of young
stellar objects, etc. This study is based mainly on optical ESO NTT
observations, both imaging and spectroscopy, coupled with other
archive data, notably Spitzer images (IRAC 3.6, 4.5, 5.8, and 8.0
microns) and 2MASS observations. We show the presence of two compact
H II regions, a low-excitation blob (LEB) named LMC N191A and a
high-excitation blob (HEB) named SMC N77A, and study their properties
and those of their exciting massive stars as far as spectral type and
mass are concerned. We also analyze the environmental stellar
populations and determine their evolutionary stages. Based on Spitzer
IRAC data, we characterize the YSO candidates detected in the
direction of these regions. Massive star formation is going on in
these young regions with protostars of mass about 10 and 20 M_sun in
the process of formation.
Reference: A&A
Status:
Manuscript has been accepted
Weblink:
http://arxiv.org/abs/1206.5939
Comments:
Email: romain.selier@obspm.fr
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Alexandre David-Uraz (1),
Anthony F. J. Moffat (1), André-Nicolas Chené (2,3), Jason F. Rowe
(4), Nicholas Lange (5), David B. Guenther (6), Rainer Kuschnig
(7,8), Jaymie M. Matthews (8), Slavek M. Rucinski (9), Dimitar
Sasselov (10), Werner W. Weiss (7)
1) Université de
Montréal
2) Universidad de Concepcion
3) Universidad de
Valparaiso
4) NASA Ames
5) University of Victoria
6)
Saint Mary's University
7) University of Vienna
8) University
of British Columbia
9) University of Toronto
10) Harvard
CfA
The WR binary CV Serpentis (= WR113, WC8d + O8-9IV) has
been a source of mystery since it was shown that its atmospheric
eclipses change with time over decades, in addition to its sporadic
dust production. The first high-precision time-dependent photometric
observations obtained with the MOST space telescope in 2009 show two
consecutive eclipses over the 29d orbit, with varying depths. A
subsequent MOST run in 2010 showed a seemingly asymmetric eclipse
profile. In order to help make sense of these observations, parallel
optical spectroscopy was obtained from the Mont Megantic Observatory
(2009, 2010) and from the Dominion Astrophysical Observatory (2009).
Assuming these depth variations are entirely due to electron
scattering in a beta-law wind, an unprecedented 62% increase in
mass-loss rate is observed over one orbital period. Alternatively, no
change in mass-loss rate would be required if a relatively small
fraction of the carbon ions in the wind globally recombined and
coaggulated to form carbon dust grains. However, it remains a mystery
as to how this could occur. There also seems to be evidence for the
presence of corotating interaction regions (CIR) in the WR wind: a
CIR-like signature is found in the light curves, implying a potential
rotation period for the WR star of 1.6 d. Finally, a new circular
orbit is derived, along with constraints for the wind
collision.
Reference: MNRAS
Status: Manuscript has
been accepted
Weblink:
http://arxiv.org/abs/1207.6032
Comments:
11 pages, 11 figures, 5 tables
Email:
alexandre@astro.umontreal.ca
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Michel Curé(1), Lydia
Cidale(2) & Diego F. Rial(3)
(1) Universidad de
Valparaıso, Chile
(2) Universidad Nacional de La Plata &
Instituto de Astrofısica La Plata, CONICET-UNLP, Argentina
(3)
Universidad de Buenos Aires, Argentina
We calculated the
influence of the limb-darkened finite disk correction factor in the
theory of radiation-driven winds from massive stars. We solved the
1-D m-CAK hydrodynamical equation of rotating radiation-driven winds
for all three known solutions, i.e., fast, Omega-slow and delta-slow.
We found that for the fast solution, the mass loss rate is increased
by a factor ∼ 10%, while the terminal velocity is reduced about
10%, when compared with the solution using a finite disk correction
factor from a uniformly bright star. For the other two slow solutions
the changes are almost negligible.
Although, we found that
the limb darkening has no effects on the wind momentum luminosity
relationship, it would affect the calculation of synthetic line
profiles and the derivation of accurate wind parameters.
Reference:
ApJ
Status: Manuscript has been accepted
Weblink:
http://xxx.lanl.gov/abs/1207.6009
Comments:
19 pages, 6 figures
Email: michel.cure@uv.cl
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H. Sana (1,*), S.E. de Mink
(2,3†), A. de Koter (1,4), N. Langer (5), C.J. Evans (6), M. Gieles
(7), E. Gosset (8), R.G. Izzard (5), J.-B. Le Bouquin (9), F.R.N.
Schneider (5)
1. Astronomical Institute 'Anton Pannekoek',
Amsterdam University, Science Park 904, 1098 XH, Amsterdam, The
Netherlands
2. Space Telescope Science Institute, 3700 San Martin
Drive, Baltimore, MD 21218 USA
3. Department of Physics and
Astronomy, Johns Hopkins University, Baltimore, MD 21218, USA
4.
Astronomical Institute, Utrecht University, Princetonplein 5, 3584
CC, Utrecht, The Netherlands
5. Argelander-Institut für
Astronomie, Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany
6. UK Astronomy Technology Centre, Royal Observatory Edinburgh,
Blackford Hill, Edinburgh, EH9 3HJ, UK
7. Institute of Astronomy,
University of Cambridge, Madingley Road, Cambridge CB3 0HA, United
Kingdom
8. F.R.S.-FNRS, Institut d'Astrophysique, Liège
University, Allée du 6 Août 17, B-4000 Liège, Belgium
9.
UJF-Grenoble 1 / CNRS-INSU, Institut de Planétologie et
d'Astrophysique de Grenoble (IPAG) UMR 5274, Grenoble, France
*Correspondence to: H.Sana@uva.nl
†Hubble Fellow
The
presence of a nearby companion alters the evolution of massive stars
in binary systems, leading to phenomena such as stellar mergers,
X-ray binaries and gamma-ray bursts. Unambiguous constraints on the
fraction of massive stars affected by binary interaction were
lacking. We simultaneously measured all relevant binary
characteristics in a sample of Galactic massive O stars and
quantified the frequency and nature of binary interactions. Over
seventy per cent of all massive stars will exchange mass with a
companion, leading to a binary merger in one third of the cases.
These numbers greatly exceed previous estimates and imply that binary
interaction dominates the evolution of massive stars, with
implications for populations of massive stars and their
supernovae.
Reference: Sana et al., Science, 337,
444-446 (2012)
Status: Manuscript has been accepted
Weblink:
http://www.sciencemag.org/content/337/6093/444.full
Comments:
Email: H.Sana@uva.nl
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Fabrice Martins$^1$, John
Hillier$^2$
1- LUPM, CNRS & Montpellier University; 2-
University of Pittsburgh
We investigate the formation of CIII
4647-51-50 and CIII 5696 in the atmosphere of O stars to see if they
can be reliably used for abundance determinations. We use atmosphere
models computed with the code CMFGEN. The key physical ingredients
explaining the formation of the CIII lines are extracted from
comparisons of models with different stellar parameters and through
examining rates controlling the level populations. The strength of
CIII 5696 critically depends on UV CIII lines at 386, 574 and 884 A.
These lines control the CIII 5696 upper and lower level population.
CIII 884 plays a key role in late O stars where it drains the lower
level of CIII 5696. CIII 386 and CIII 574 are more important at early
spectral types. The overlap of these UV lines with FeIV 386.262, FeIV
574.232 and SV 884.531 influences the radiative transfer at 386, 574
and 884 A, and consequently affects the strength of CIII 5696. CIII
4650 is mainly controlled by the CIII 538 line which acts as a drain
on its lower level. FeIV 538.057 interacts with CIII 538 and has an
impact on the CIII 4650 profile. Low temperature dielectronic
recombinations have a negligible effect on the line profiles. Given
our current understanding of the stellar and wind properties of O
stars, and in view of the present results, the determination of
accurate carbon abundances from CIII 4647-51-50 and CIII 5696 is an
extremely challenging task. Uncertainties lower than a factor of two
on C/H determinations based only on these two sets of lines should be
regarder as highly doubtful. Our results provide a possible
explanation of the variability of CIII 4650 in Of?p
stars.
Reference: Astronomy and Astrophysics
Status:
Manuscript has been accepted
Weblink:
http://arxiv.org/abs/1208.0152
Comments:
Email: fabrice.martins@univ-montp2.fr
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David P. Huenemoerder, Lidia M.
Oskinova, Richard Ignace, Wayne L. Waldron, Helge Todt, Kenji
Hamaguchi, Shunji Kitamoto
Massachusetts Institute of
Technology, Kavli Institute for Astrophysics and Space Research, 70
Vassar St., Cambridge, MA 02139, USA
mu Columbae is a
prototypical weak-wind O-star for which we have obtained a
high-resolution X-ray spectrum with the Chandra LETG/ACIS-S
instrument and a low resolution spectrum with Suzaku. This allows us,
for the first time, to investigate the role of X-rays on the wind
structure in a bona fide weak-wind system and to determine whether
there actually is a massive, hot wind. The X-ray emission measure
indicates that the outflow is an order of magnitude greater than that
derived from UV lines and is commensurate with the nominal
wind-luminosity relationship for O-stars. Therefore, the ``weak-wind
problem''---identified from cool wind UV/optical spectra---is largely
resolved by accounting for the hot wind seen in X-rays. From X-ray
line profiles, Doppler shifts, and relative strengths, we find that
this weak-wind star is typical of other late O dwarfs. The X-ray
spectra do not suggest a magnetically confined plasma---the spectrum
is soft and lines are broadened; Suzaku spectra confirm the lack of
emission above 2 keV. Nor do the relative line shifts and widths
suggest any wind decoupling by ions. The He-like triplets indicate
that the bulk of the X-ray emission is formed rather close to the
star, within 5 stellar radii. Our results challenge the idea that
some OB stars are ``weak-wind'' stars that deviate from the standard
wind-luminosity relationship. The wind is not weak, but it is hot and
its bulk is only detectable in X-rays.
Reference:
ApJL
Status: Manuscript has been accepted
Weblink:
http://de.arxiv.org/abs/1208.0820
Comments:
Email: dph@space.mit.edu
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Anthony Moffat
Département de physique
Université de Montréal
C.P. 6128, Succ. C-V
Montréal,
QC, H3C 3J7
Canada
As part of a programme to train Highly
Qualified Personnel financed by a grant from the Canadian Space
Agency, the Canadian wing of the BRITE-Constellation
(http://www.brite-constellation.at/ ) science team is opening a
post-doctoral position at the Université de Montréal (Québec,
Canada). The candidate is expected to carry out original research in
stellar variability using the soon-to-be launched BRITE
nanosatellites and master the techniques of time-dependent
high-precision photometry from space. Interaction with other members
of the Centre for Research in Astrophysics of Québec
(http://craq-astro.ca/index_en.php ), as well as the three other
Canadian and eight other international BRITE team members and their
associates is encouraged. A PhD in physics or astronomy is required.
Potential candidates with the required expertise are encouraged
to apply. Please send CV, research proposal, cover letter and contact
details of two referees (including email addresses) to the Canadian
BRITE PI Dr. Anthony Moffat (moffat@astro.umontreal.ca ). The
position is open from as early as September 1st, 2012 and no later
than January 1st, 2013 for two years with a possible extension of one
year.
Attention/Comments:
Weblink:
Email:
moffat@astro.umontreal.ca
Deadline:
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Raphael Hirschi
Keele
University, ST5 5BG, UK
Keele University expects to appoint
two PDRAs for a duration of 3 years, in order to conduct research on
(1) theoretical nuclear astrophysics (NUCASTRO) and (2) theoretical
stellar astrophysics (3D1D).
The appointed PDRAs will work in the
group of Dr Raphael Hirschi within the Astrophysics Group at Keele
University as part of an ERC-funded project entitled “Stellar
HYdrodynamics, Nucleosynthesis and Evolution” (SHYNE). The ERC
starting grant awarded to Dr Hirschi provides funding for 2 postdocs
and 2 PhD students. The grant also provides funding for a dedicated
1500-CPU computer cluster, including 384 CPUs sharing memory via
Numascale technology.
(1) The NUCASTRO PDRA will lead the
nuclear astrophysics component of this project, which includes
large-scale, Mont-Carlo based, sensitivity studies as well as impact
studies of reaction rates relevant for the different nucleosynthesis
processes.
Applicants for the NUCASTRO PDRA should have or
expect to obtain a PhD in nuclear physics or astrophysics or a
related area and should have a demonstrated aptitude for research.
Experience in theoretical nuclear astrophysics is highly desirable.
(2) The 3D1D PDRA will lead the component of this project
related to 3D-1D modelling of stellar interiors. This will include a
range of computer simulations including 1D stellar evolution and 3D
hydrodynamics simulations with as main goal to improve modelling of
convection and rotation in stellar evolution.
Applicants for
the 3D1D PDRA should have or expect to obtain a PhD in theoretical
stellar astrophysics or a related area and should have a demonstrated
aptitude for research. Experience in stellar evolution modelling and
3D hydrodynamic simulations is highly desirable.
The two
PDRAs will also contribute to the other components of the project and
be encouraged to develop their own research program and their
leadership skills. The appointment will be made for an initial term
of 3 years (with a possible extension of 2 extra years), with a
likely starting date of November 1 2012 or as soon as possible after
that date.
Job packs available: www.keele.ac.uk/jobs,
vacancies@keele.ac.uk, Human Resources, Keele University,
Staffordshire, ST5 5BG or Fax: 01782 733471.
Further details
of the posts are available at
http://www.keele.ac.uk/vacancies/academicandresearchvacancies. Please
quote post reference when applying: (1) RE12/18NUCASTRO & (2)
RE12/17 3D1D
Closing date for applications: 30 September 2012
Interview date and format: interviews will take place
mid-October (most probably one of these dates: 10, 11, 17 or 18
October, to be confirmed) and interviews will be conducted remotely
(e.g. via skype).
For further enquiries please contact Dr
Raphael Hirschi at r.hirschi@epsam.keele.ac.uk.
Attention/Comments:
Weblink:
http://www.keele.ac.uk/vacancies/academicandresearchvacancies
Email:
r.hirschi@epsam.keele.ac.uk
Deadline: 30 September
2012
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Sept. 25.- 26.
Venue:
University of Hamburg
Some stars are born and die hot,
while some stars become hot as they evolve. The strong UV radiation
of hot stars ionizes the surrounding medium and drives stellar winds.
This input of radiative and mechanic energy affects the circumstellar
matter and the ISM, and may even decide the fate of a star cluster.
The advance in theory and multiwavelength observations provides new
insights into the physics of hot stars, their evolution, atmospheres,
winds, and feedback. This splinter meeting aims at bringing together
the hot star community to review the methods and the models used for
the studies of hot stars, and to discuss and plan the observational
facilities and programs needed for the studies of hot stars. Special
attention will be devoted to the hot topics in the field which are
likely to be in the focus of the community in the near
future.
Weblink:
http://www.hs.uni-hamburg.de/AG2012/index.php?option=com_content&view=article&id=37&Itemid=265〈=en
Email:
htodt@astro.physik.uni-potsdam.de
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September 16th-19th
2012
Venue: STScI, Baltimore, USA
The 30
Doradus or Tarantula Nebula region of the Large Magellanic Cloud is
synonymous with many superlatives in astronomy, hosting as it does
the most massive young resolved cluster (R136), the most massive
stars yet discovered, the fastest rotating O-type stars, the most
massive runaway star.
Its unique accessibility to detailed
study covering the electromagnetic spectrum from X-ray, UV, optical,
IR through radio is reflected in the many detailed surveys of this
region with facilities such as HST, Chandra, Spitzer, VLT-Flames and
VISTA. While it is certainly a challenge to understand this wealth of
information for what is a very complex region it is one well worth
addressing since 30 Doradus may have much to teach us about more
distant unresolved starbursts and super star clusters.
The
aim of this mini-workshop is to review recent results and outstanding
theoretical issues and to examine the extent to which our knowledge
of 30 Doradus can be used to improve our understanding of distant
starbursts and star clusters. It will focus on five closely related
themes; formation, environment, content, evolution, and relevance to
Super Star Clusters and Starbursts.
SOC at STScI: Selma de
Mink, Linda Smith, Karl Gordon, Nolan Walborn, Danny Lennon (chair),
Brad Whitmore, Elena Sabbi, Aida Wofford, Sherita Hanna (coordinator)
Registration deadline: August 17th 2012
Weblink:
http://www.stsci.edu/institute/conference/doradus
Email:
lennon@stsci.edu
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November 26-29, 2012
Venue: Paris
Observatory, France
Mass loss from evolved massive stars is a
major contributor to the chemical enrichment of the interstellar
medium, the Galaxy, and ultimately the Universe. To have a clear view
of their cosmic impact, it is essential to understand their physics,
from the photosphere to the interstellar medium (ISM). Thanks to its
proximity and brightness, Betelgeuse is a particularly important
fiducial object to study in details the physical phenomena at play in
red supergiants (RSGs).
The goal of the workshop is to assemble a
comprehensive description of the different regions constitutive of
Betelgeuse, to understand how they interact with each other, and
eventually how red supergiants are functioning.
We aim at a
genuine workshop format with many opportunities for exchanges among
50 participants who actively carry out research on Betelgeuse and
similar objects. Each session will start with an invited overview
talk and will be closed by a discussion.
Weblink:
http://betelgeuse.sciencesconf.org/
Email:
betelgeuse@sciencesconf.org
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September 30 - October 3, 2012
Venue: St.
Paul, MN, USA
The meeting will be a three day topical workshop
to bring together theorists and observers studying very massive
stars, their instabilities, SNe and their progenitors, and the
outcomes of the final eruptions. The emphasis of the workshop will be
on the final stages of massive star evolution and the unsolved
theoretical and observational questions.
Weblink:
www.astro.umn.edu/massive
Email:
massive@astro.umn.edu
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