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Call for organizing the next massive star meeting (2017)
UV diagnostic of porosity-free
mass-loss estimates in B stars
Catalogue
of particle-accelerating colliding-wind binaries
Self-Sealing
Shells: Blowouts and Blisters on the Surfaces of Leaky
Wind-Blown-Bubbles and Supernova Remnants
The
VLT-FLAMES Tarantula Survey XII. Rotational velocities of the single
O-type stars
Modelling the
asymmetric wind of the luminous blue variable binary MWC 314
The
Ionized Nebula surrounding the Red Supergiant W26 in Westerlund
1
Macroclumping as solution of the
discrepancy between H-alpha and P v mass loss diagnostics for O-type
stars
Dynamics of H II regions
around exiled O stars
Constraints
on decreases in Eta Carinae's mass loss from 3D hydrodynamic
simulations of its binary colliding winds
Revealing
the Asymmetry of the Wind of the Variable Wolf-Rayet
Progenitors
of supernova Ibc: a single Wolf-Rayet star as the possible progenitor
of the SN Ib iPTF13bvn
WR 138: new
results from X-ray and optical spectroscopy
Classical
Be Stars: Rapidly Rotating B Stars with Viscous Keplerian Decretion
Disks
The Massive Star Population
in M101. I. The Identification and Spatial Distribution of the
Visually Luminous Stars
Non-thermal
radio emission from O-type stars. V. 9 Sgr
Stellar
mass-loss near the Eddington limit. Tracing the sub-photospheric
layers of classical Wolf-Rayet stars
The
rotation rates of massive stars: How slow are the slow ones?
One
of the most massive stars in the Galaxy may have formed in
isolation
A comparison of
evolutionary tracks for single Galactic massive stars
Fundamental
properties of core-collapse supernova and GRB progenitors: predicting
the look of massive stars before death
The VLT-FLAMES Tarantula Survey. XIV: On the nature of O,V z stars in 30 Doradus
Rotational properties of the O-type star population in the Tarantula region
POSTDOCTORAL POSITION IN MASSIVE STARS
The Space
Photometry Revolution
Eta Carina
Coordination Meeting January 9, 10, 2014:
Dear colleagues,
this
is a reminder that the Organizing Committee of the Massive Star
Working Group will consider
proposals for the organization of the
next Massive Star Symposium before October 15.
after the
fantastic meeting in Rhodes (thanks to Alceste Bonanos and
Danny
Lennon as organizers) we have to start preparing the next
Massive
Stars Meeting. We foresee that this meeting will probably take place
in 2017.
With this call the Organizing Committee of our
Massive Stars Working Group
invites any interested people to send
an email before next October 15th
communicating his/her interest
in organizing the next meeting.
The email shall be sent to me as
chair of the OC (ahd-at-iac.es).
We do not want that anyone
spends too much time and effort with
the proposals. A short email
indicating the willingness to organize the meeting
with some
comments about the adequacy of the proposed place will
be enough.
The OC will consider all proposals and select one of the
proposed places
before end of the year, based on criteria like:
- the meeting location (traditionally, our group prefers
locations near a beach where
a relaxed atmosphere favours
personal contacts)
- the availability of hotels with large
conference rooms (at least 200 people)
and meeting facilities at
affordable prices
- the support of a local astronomical community
- the balance of locations hosting our meetings
best
regards,
Artemio Herrero
chair of the Organizing Committee of
the IAU Massive Stars Working Group
Weblink:
Email:
ahd@iac.es
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Raman Prinja and Derck
Massa
Department of Physics & Astronomy, UCL, Gower
Street, London, WC1E 6BT, UK
Space Science Institute (SSI),
4750 Walnut St., Boulder, Colorado 80301, USA
We seek to
establish evidence in UV P Cygni line profiles that the signs of wind
clumping and porosity vary with velocity. We aim to demonstrate
empirically that while at most wind velocities optically thick clumps
cover only a fraction of the stellar surface, close to the terminal
velocity where narrow absorption components (NACs) appear in UV lines
the covering factor is approximately unity. SEI line-synthesis models
are used to determine the radial optical depths of blue and red
components of the SiIV 1400 resonance line doublet in a sample of 12
B0 to B4 supergiants. We focus on stars with well developed NACs and
relatively low terminal velocity so that the SiIV doublet components
can be treated as radiatively decoupled and formed independently. For
all 12 stars the mean optical depth ratio of the blue to red
components is closer to ~ 2 (i.e. the ratio of oscillator strengths)
in the NACs than at intermediate and lower velocities. The product of
mass-loss rate and Si^3+ ion fraction calculated from the NAC optical
depths is a factor of ~ 2 to 9 higher compared to mass-loss values
sampled at ~ 0.4 to 0.6 of the terminal velocity. Since the wind
effectively becomes `smooth' at the high NAC velocities and the
column density is uniformly distributed over the stellar disk, the
optical depths of the NACs are not seriously affected by porosity and
this feature thus provides the most reliable measurement of mass-loss
rate in the UV lines. Applications of this result to the weak-wind
problem of late O-dwarf stars and the ``PV mass loss discordance'' in
early O supergiants are discussed.
Reference: A&A
in press
Status: Manuscript has been accepted
Weblink:
http://arxiv.org/abs/1309.2095
Comments:
Email: rkp@star.ucl.ac.uk
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De Becker M. & Raucq
F.
Department of Astrophysics, Geophysics and
Oceanography, University of Liège, Belgium
Massive systems
made of two or more stars are known to be the site for interesting
physical processes - including at least in some cases - particle
acceleration. Over the past decade, this topic motivated a particular
effort to unveil the properties of these systems and characterize the
circumstances responsible for the acceleration of particles and the
potential role of pre-supernova massive stars in the production of
high energy particles in our Galaxy. Although previous studies on
this topic were mostly devoted to processes in general, or to a few
individual objects in particular, a unified target-oriented census of
particle-accelerating colliding-wind binaries (hereafter PACWBs) does
not exist yet. This paper aims at making a general and unified census
of these systems, emphasizing their main properties. A general
discussion includes energetic considerations along with wind
properties in relation with non-thermal emission processes that are
likely at work in colliding-wind binaries. Finally, some guidelines
for future observational and theoretical studies are
drawn.
Reference: Astronomy & Astrophysics (in
press)
Status: Manuscript has been accepted
Weblink:
http://hdl.handle.net/2268/154330
Comments:
A&A forthcoming paper link:
http://dx.doi.org/10.1051/0004-6361/201322074
Email:
debecker@astro.ulg.ac.be
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contents
J.M. Pittard
The
University of Leeds
Blowouts can occur when a dense shell
confining hot, high pressure,
gas ruptures. The venting gas
inflates a blister on the surface of
the shell. Here we examine
the growth of such blisters on the
surfaces of wind-blown-bubbles
(WBBs) and supernova remnants (SNRs)
due to shell rupture caused
by the Vishniac instability. On WBBs the
maximum relative size of
the blister ($R_{rm bstall}/R$) is found
to grow linearly with
time, but in many cases the blister radius
will not exceed 20 per
cent of the bubble radius. Thus blowouts
initiated by the
Vishniac instability are unlikely to have a major
effect on the
global dynamics and properties of the bubble. The
relative size
of blisters on SNRs is even smaller than on WBBs, with
blisters
only growing to a radius comparable to the thickness of the
cold
shell of SNRs. The small size of the SNR blowouts is, however,
in
good agreement with observations of blisters in the Vela SNR. The
difference in relative size between WBB and SNR blisters is due
to
the much higher speed at which gas vents out of WBBs, which
translates into a greater energy flux through a rupture of a
given
size from interior gas of a given pressure. Larger blisters
are
possible if shell ruptures are bigger than expected.
We
expect the observed velocity structure of SNR shells to be
affected
by the presence of blisters until the shell is no longer
susceptible
to ruptures, since the initial expansion of blisters is
faster
than the ongoing expansion of the shell.
Reference: MNRAS,
in press
Status: Manuscript has been accepted
Weblink:
http://arxiv.org/abs/1308.3392
Comments:
Manuscript has been accepted
Email:
jmp@ast.leeds.ac.uk
Back to contents
O.H.
Ram'{i}rez-Agudeloinst{1}, S. Sim'on-D'{i}az inst{2,3}, H. Sana
inst{1,4}, A. de Koter inst{1,5}, C. Sab'{i}n-Sanjul'{i}an inst{2,3},
S.E. de Mink inst{6,7}, P. L. Dufton inst{8}, G. Gr"afener
inst{9}, C.J. Evans inst{10}, A. Herrero inst{2,3}, N. Langer
inst{11}, D.J. Lennon inst{12}, J. Ma'{i}z Apell'aniz inst{13}, N.
Markova inst{14}, F. Najarro inst{15}, J. Puls inst{16}, W.D. Taylor
inst{10}, J.S. Vink inst{9}
^{1} Astronomical Institute
Anton Pannekoek, Amsterdam University, Science Park 904, 1098~XH,
Amsterdam, The Netherlands
^{2} nstituto de Astrof'{i}sica de
Canarias, C/ V'{i}a L'{a}ctea s/n, E-38200 La Laguna, Tenerife, Spain
^{3} Departamento de Astrof'{i}sica, Universidad de La Laguna,
Avda. Astrof'{i}sico Francisco S'{a}nchez s/n, E-38071 La Laguna,
Tenerife, Spain
^{4} Space Telescope Science Institute, 3700 San
Martin Drive, Baltimore, MD 21218, USA
^{5} Instituut voor
Sterrenkunde, Universiteit Leuven, Celestijnenlaan 200 D, 3001,
Leuven, Belgium
^{6} Observatories of the Carnegie Institution
for Science, 813 Santa Barbara St, Pasadena, CA 91101, USA
^{7}
Cahill Center for Astrophysics, California Institute of Technology,
Pasadena, CA 91125, USA
^{8} Astrophysics Research Centre, School
of Mathematics and Physics, Queen's University of Belfast, Belfast
BT7 1NN, UK
^{9} Armagh Observatory, College Hill, Armagh, BT61
9DG, Northern Ireland, UK
^{10} UK Astronomy Technology Centre,
Royal Observatory Edinburgh, Blackford Hill, Edinburgh, EH9 3HJ, UK
^{11} Argelander-Institut f"ur Astronomie, Universit"at
Bonn, Auf dem H"ugel 71, 53121 Bonn, Germany
^{12} European
Space Astronomy Centre (ESAC), Camino bajo del Castillo, s/n
Urbanizacion Villafranca del Castillo, Villanueva de la Ca~nada,
E-28692 Madrid, Spain
^{13} nstituto de Astrof'{i}sica de
Andaluc'{i}a-CSIC, Glorieta de la Astronom'ia s/n, E-18008 Granada,
Spain
^{14} Institute of Astronomy with NAO, Bulgarian Academy of
Science, PO Box 136, 4700 Smoljan, Bulgaria
^{15} Centro de
Astrobiolog'{i}a (CSIC-INTA), Ctra. de Torrej'on a Ajalvir km-4,
E-28850 Torrej'on de Ardoz, Madrid, Spain
^{16}
Universit"atssternwarte, Scheinerstrasse 1, 81679 M"unchen,
Germany
% context heading (optional)
% {} leave it empty
if necessary resultsssss
{The 30 Doradus (30,Dor) region of the
Large Magellanic Cloud, also known as the Tarantula Nebula, is the
nearest starburst region. It contains the richest population of
massive stars in the Local Group and it is thus
the best possible
laboratory to investigate open questions in the formation and
evolution of massive stars.}
% aims heading (mandatory)
{Using
ground based multi-object optical spectroscopy obtained in the
framework of the VLT-FLAMES Tarantula Survey (VFTS), we aim to
establish the (projected) rotational velocity distribution for a
sample of 216 presumably single O-type stars in 30 Dor. The size of
the sample is large enough to obtain statistically significant
information and to search for variations among sub-populations -- in
terms of spectral type, luminosity class, and spatial location -- in
the field of view.}
% methods heading (mandatory)
{We
measured projected rotational velocities, vrot, by means of a Fourier
transform method and a profile fitting
method applied on a set of
isolated spectral lines. We also used an iterative deconvolution
procedure to infer the probability density,
$rm{P(veq)}$, of the
equatorial rotational velocity, veq.}
% results heading
(mandatory)
{The distribution of vrot shows a two-component
structure: a peak around 80~kms
and a high-velocity tail
extending up to $sim$600 kms. This structure is also present in the
inferred distribution $rm{P(veq)}$
with around 80% of the sample
having 0 $<$ veq, $leq, 300$~kms and the other 20% distributed in
the high-velocity
region. The presence of the low-velocity peak
is consistent with that found in other studies for late O- and early
B-type stars. }
% conclusions heading (optional), leave it empty
if necessary
{Most of the stars in our sample rotate with a rate
less than 20% of their break-up velocity.
For the bulk of the
sample, mass-loss in a stellar wind and/or envelope expansion is not
efficient enough
to significantly spin down these stars within
the first few Myr of evolution. If massive-star formation
results
in stars rotating at birth with a large fraction of their break-up
velocities, an alternative
braking mechanism, possibly magnetic
fields, is thus required to explain the present day rotational
properties of the O-type stars in 30,Dor. The presence of a
sizeable population of fast rotators is
compatible with recent
population synthesis computations that investigate the influence of
binary evolution
on the rotation rate of massive stars. Despite
the fact that we have excluded stars that show significant
radial
velocity variations, our sample may have remained contaminated by
post-interaction binary products.
The fact that the high-velocity
tail may be preferentially (and perhaps even exclusively), populated
by
post-binary interaction products, has important implications
for the evolutionary origin of systems
that produce gamma-ray
bursts.
}
Reference: A&A (in press)
Status:
Manuscript has been accepted
Weblink:
http://adsabs.harvard.edu/abs/2013arXiv1309.2929R
Comments:
Accepted for publication in Astronomy & Astrophysics
Email:
o.h.ramirezagudelo@uva.nl
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contents
A. Lobel (1), J. H. Groh (2),
C. Martayan (3), Y. Fremat (1), K. Torres Dozinel (4), G. Raskin (5),
H. Van Winckel (5), S. Prins (5), W. Pessemier (5), C. Waelkens (5),
H. Hensberge (1), L. Dumortier (1), A. Jorissen (6), S. Van Eck (6),
and H. Lehmann (7)
(1) Royal Observatory of Belgium,
Ringlaan 3, B-1180 Brussels, Belgium
(2) Geneva Observatory,
Geneva University, Chemin des Maillettes 51, CH-1290 Sauverny,
Switzerland
(3) European Southern Observatory, Alonso de Cordova
3107, Vitacura, Santiago, Chile
(4) University of Sao Joao Del
Rei, CAP, 36420-000 Ouro Branco, MG, Brazil
(5) University of
Leuven, Instituut voor Sterrenkunde, Celestijnenlaan 200 D, B-3001
Heverlee, Belgium
(6) Universite Libre de Bruxelles, Boulevard du
Triomphe, B-1050, Brussels, Belgium
(7) Thuringer
Landessternwarte, Sternwarte 5, D-07778 Tautenburg, Germany
We
present a spectroscopic analysis of MWC 314, a luminous blue variable
(LBV) candidate with an extended bipolar nebula. The detailed
spectroscopic variability is investigated to determine if MWC 314 is
a massive binary system with a supersonically accelerating wind or a
low-mass B[e] star. We compare the spectrum and spectral energy
distribution to other LBVs (such as P Cyg) and find very similar
physical wind properties, indicating strong kinship.
We combine
long-term high-resolution optical spectroscopic monitoring and V-band
photometric observations to determine the orbital elements and
stellar parameters and to investigate the spectral variability with
the orbital phases. We develop an advanced model of the large-scale
wind-velocity and wind-density structure with 3-D radiative transfer
calculations that fit the orbitally modulated P Cyg profile of He I
lamb5876, showing outflow velocities above 1000 km/s.
We find
that MWC 314 is a massive semi-detached binary system of ~1.22 AU,
observed at an inclination angle of i=72.8 deg. with an orbital
period of 60.8 d and e=0.23. The primary star is a low-vsini LBV
candidate of m1=39.6 Msun and R1=86.8 Rsun. The detailed radiative
transfer fits show that the geometry of wind density is asymmetric
around the primary star with increased wind density by a factor of
3.3, leading the orbit of the primary. The variable orientation
causes the orbital modulation that is observed in absorption portions
of P Cyg wind lines. Wind accretion in the system produces a
circumbinary disc.
MWC 314 is in a crucial evolutionary phase of
close binary systems, when the massive primary star has its H
envelope being stripped and is losing mass to a circumbinary disk.
MWC 314 is a key system for studying the evolutionary consequences of
these effects.
Reference: Astronomy and Astrophysics,
Main Journal
Status: Manuscript has been accepted
Weblink:
http://dx.doi.org/10.1051/0004-6361/201220421
Comments:
http://arxiv.org/abs/1308.4638
Email:
Alex.Lobel@oma.be
Back to contents
Nicholas J. Wright, Roger
Wesson, Janet E. Drew, Geert Barentsen, Michael J. Barlow, Jeremy R.
Walsh, Albert Zijlstra, Jeremy J. Drake, Jochen Eisloffel, Hywel J.
Farnhill
University of Hertfordshire
We present
Halpha images of an ionized nebula surrounding the M2-5Ia red
supergiant (RSG) W26 in the massive star cluster Westerlund 1. The
nebula consists of a circumstellar shell or ring ~0.1pc in diameter
and a triangular nebula ~0.2pc from the star that in high-resolution
Hubble Space Telescope images shows a complex filamentary structure.
The excitation mechanism of both regions is unclear since RSGs are
too cool to produce ionizing photons and we consider various
possibilities. The presence of the nebula, high stellar luminosity
and spectral variability suggest that W26 is a highly evolved RSG
experiencing extreme levels of mass-loss. As the only known example
of an ionized nebula surrounding a RSG W26 deserves further attention
to improve our understanding of the final evolutionary stages of
massive stars.
Reference: MNRAS, in press
Status:
Manuscript has been accepted
Weblink:
http://arxiv.org/abs/1309.4086
Comments:
Email: nick.nwright@gmail.com
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B. Surlan(1,2), W.-R.
Hamann(3), A. Aret(4), J. Kubat(1), L. M. Oskinova(3), A. F.
Torres(5,6)
1-Astronomicky ustav, Akademie ved Ceske
Republiky, CZ-251 65 Ondrejov, Czech Republic
2-Matematicki
Institut SANU, Kneza Mihaila 36, 11001 Beograd, Republic of Serbia
3-Institut fur Physik und Astronomie, Universitat Potsdam,
Karl-Liebknecht-Strase 24/25, 14476 Potsdam-Golm, Germany
4-Tartu
Observatory, 61602, Toravere, Tartumaa, Estonia
5-Departamento de
Espectroscopia, Facultad de Ciencias Astronomicas y Geofisicas,
Universidad Nacional de La Plata, Paseo del Bosque S/N, La Plata,
B1900FWA, Buenos Aires, Argentina
6-Instituto de Astrofisica de
La Plata (CCT La Plata - CONICET, UNLP), Paseo del Bosque S/N, La
Plata, B1900FWA, Buenos Aires, Argentina
Recent studies of
O-type stars demonstrated that discrepant mass-loss rates are
obtained when different diagnostic methods are employed - fitting the
unsaturated UV resonance lines (e.g. P v) gives drastically lower
values than obtained from the H-alpha emission. Wind inhomogeneity
(so-called ``clumping'') may be the main cause for this
discrepancy. In a previous paper, we have presented 3-D Monte-Carlo
calculations for the formation of scattering lines in a clumped
stellar wind. In the present paper we select five O-type supergiants
(from O4 to O7) and test whether the reported discrepancies can be
resolved this way. In the first step, the analyses start with
simulating the observed spectra with Potsdam Wolf-Rayet (PoWR)
non-LTE model atmospheres. The mass-loss rates are adjusted to fit
best to the observed H-alpha emission lines. For the unsaturated UV
resonance lines (i.e. P v) we then apply our 3-D Monte-Carlo code,
which can account for wind clumps of any optical depths
(``macroclumping''), a non-void inter-clump medium, and a velocity
dispersion inside the clumps. The ionization stratifications and
underlying photospheric spectra are adopted from the PoWR models.
From fitting the observed resonance line profiles, the properties of
the wind clumps are constrained. Our results show that with the
mass-loss rates that fit H-alpha (and other Balmer and He II lines),
the UV resonance lines (especially the unsaturated doublet of P v)
can also be reproduced without problem when macroclumping is taken
into account. There is no need to artificially reduce the mass-loss
rates, nor to assume a sub-solar phosphorus abundance or an extremely
high clumping factor, contrary to what was claimed by other authors.
These consistent mass-loss rates are lower by a factor of 1.3 to 2.6,
compared to the mass-loss rate recipe from Vink et al. Macroclumping
resolves the previously reported discrepancy between H-alpha and P v
mass-loss diagnostics.
Reference: Accepted for
publication in A&A (in press)
Status: Manuscript has been
accepted
Weblink: http://arxiv.org/abs/1310.0449
Email:
surlan@sunstel.asu.cas.cz
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Jonathan Mackey$^1$, Norbert
Langer$^1$, Vasilii V. Gvaramadze$^{2,3}$
1 -
Argelander-Institut fuer Astronomie, Auf dem Huegel 71, 53121 Bonn,
Germany
2 - Sternberg Astronomical Institute, Lomonosov Moscow
State University, Universitetskij Pr. 13, Moscow 119992, Russia.
3
- Isaac Newton Institute of Chile, Moscow Branch, Universitetskij Pr.
13, Moscow 119992, Russia.
At least 25 per cent of massive
stars are ejected from their parent cluster, becoming runaways or
exiles, travelling with often-supersonic space velocities through the
interstellar medium (ISM). Their overpressurised H II regions impart
kinetic energy and momentum to the ISM, compress and/or evaporate
dense clouds, and can constrain properties of both the star and the
ISM. Here we present one-, two-, and (the first) three-dimensional
simulations of the H II region around a massive star moving
supersonically through a uniform, magnetised ISM, with properties
appropriate for the nearby O star Zeta Oph. The H II region leaves an
expanding overdense shell behind the star and, inside this, an
underdense wake that should be filled with hot gas from the shocked
stellar wind. The gas column density in the shell is strongly
influenced by the ISM magnetic field strength and orientation.
H-alpha emission maps show the H II region remains roughly circular,
although the star is displaced somewhat from the centre of emission.
For our model parameters, the kinetic energy feedback from the H II
region is comparable to the mechanical luminosity of the stellar
wind, and the momentum feedback rate is >100X larger than that
from the wind and about 10X larger than the total momentum input rate
available from radiation pressure. Compared to the star's eventual
supernova explosion, the kinetic energy feedback from the H II region
over the star's main sequence lifetime is >100X less, but the
momentum feedback is up to 4X larger. H II region dynamics are found
to have only a small effect on the ISM conditions that a bow shock
close to the star would encounter.
Reference: MNRAS in
press, arXiv:1308.5192
Status: Manuscript has been
accepted
Weblink:
http://adsabs.harvard.edu/abs/2013MNRAS.tmp.2269M
Comments:
Email: jmackey@astro.uni-bonn.de
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Thomas I. Madura(1,*),
Theodore R. Gull(1), Atsuo T. Okazaki(2), Christopher M.P.
Russell(2), Stanley P. Owocki(3), Jose H. Groh(4), Michael F.
Corcoran(1), Kenji Hamaguchi(1), Mairan Teodoro(1,5)
1 -
NASA GSFC
2 - Hokkai-Gakuen University, Sapporo, Japan
3 -
University of Delaware
4 - Geneva Observatory
5 -
CNPq/Science without Borders Fellow
* - NASA Postdoctoral Program
Fellow
Recent work suggests that the mass-loss rate of the
primary star (Eta A) in the massive colliding wind binary Eta Carinae
dropped by a factor of 2-3 between 1999 and 2010. We present results
from large- (r=1545au) and small- (r=155au) domain, 3D smoothed
particle hydrodynamic (SPH) simulations of Eta Car's colliding winds
for 3 Eta A mass-loss rates (2.4, 4.8, and 8.5 x 10^-4 M_sun/yr),
investigating the effects on the dynamics of the binary wind-wind
collision (WWC). These simulations include orbital motion, optically
thin radiative cooling, and radiative forces. We find that Eta A's
mass-loss rate greatly affects the time-dependent hydrodynamics at
all spatial scales investigated. The simulations also show that the
post-shock wind of the companion star (Eta B) switches from the
adiabatic to the radiative-cooling regime during periastron passage.
This switchover starts later and ends earlier the lower the value of
Eta A's mass-loss rate and is caused by the encroachment of the wind
of Eta A into the acceleration zone of Eta B's wind, plus radiative
inhibition of Eta B's wind by Eta A. The SPH simulations together
with 1D radiative transfer models of Eta A's spectra reveal that a
factor of 2 or more drop in Eta A's mass-loss rate should lead to
substantial changes in numerous multiwavelength observables. Recent
observations are not fully consistent with the model predictions,
indicating that any drop in Eta A's mass-loss rate was likely by a
factor < 2 and occurred after 2004. We speculate that most of the
recent observed changes in Eta Car are due to a small increase in the
WWC opening angle that produces significant effects because our
line-of-sight to the system lies close to the dense walls of the WWC
zone. A modest decrease in Eta A's mass-loss rate may be responsible,
but changes in the wind/stellar parameters of Eta B cannot yet be
fully ruled out. We suggest observations during Eta Car's next
periastron in 2014 to further test for decreases in Eta A's mass-loss
rate. If Eta A's mass-loss rate is declining and continues to do so,
the 2014 X-ray minimum should be even shorter than that of
2009.
Reference: MNRAS, accepted
Status: Manuscript
has been accepted
Weblink:
http://arxiv.org/abs/1310.0487
Comments:
Email: tmadura@udel.edu
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Nicole St-Louis
Université
de Montréal
In this paper, high quality spectropolarimetric
observations of the Wolf-Rayet (WR) star WR1 (HD 4004) obtained with
ESPaDOnS at the Canada-France-Hawaii Telescope are presented. All
major emission lines present in the spectrum show depolarization in
the relative Stokes parameters Q/I and U/I. From the behavior of the
amount of line depolarization as a function of line strength, the
intrinsic continuum light polarization of WR1 is estimated to be P/I
= 0.443% ± 0.028% with an angle of θ = –26.2 deg. Although such a
level of polarization could in principle be caused by a wind
flattened by fast rotation, the scenario in which it is a consequence
of the presence of corotating interaction regions (CIRs) in the wind
is preferred. This is supported by previous photometric and
spectroscopic observations showing periodic variations with a period
of 16.9 days. This is now the third WR star thought to exhibit CIRs
in its wind that is found to have line depolarization. Previous
authors have found a strong correlation between line depolarization
and the presence of an ejected nebula, which they interpret as a sign
that the star has relatively recently reached the WR phase since the
nebula are thought to dissipate very fast. In cases where the
presence of CIRs in the wind is favored to explain the depolarization
across spectral lines, the above-mentioned correlation may indicate
that those massive stars have only very recently transited from the
previous evolutionary phase to the WR phase.
Reference:
St-Louis, N. 2013, ApJ, 777, 9
Status: Manuscript has been
accepted
Weblink:
Comments:
Email:
stlouis@astro.umontreal.ca
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Jose H. Groh (1), Cyril
Georgy (2), and Sylvia Ekstrom (1)
(1) Geneva Observatory,
Switzerland
(2) Keele University, UK
Core-collapse
supernova (SN) explosions mark the end of the tumultuous life of
massive stars. Determining the nature of their progenitors is a
crucial step towards understanding the properties of SNe. Until
recently, no progenitor has been directly detected for SN of type
Ibc, which are believed to come from massive stars that lose their
hydrogen envelope through stellar winds and from binary systems where
the companion has stripped the H envelope from the primary. Here we
analyze recently reported observations of iPTF13bvn, which could
possibly be the first detection of a SN Ib progenitor based on
pre-explosion images. Very interestingly, the recently published
Geneva models of single stars can reproduce the observed photometry
of the progenitor candidate and its mass-loss rate, confirming a
recently proposed scenario. We find that a single WR star with
initial mass in the range 31-35 Msun fits the observed photometry of
the progenitor of iPTF13bvn. The progenitor likely has a luminosity
of log (L/Lsun)~5.55, surface temperature ~45000 K, and mass of ~10.9
Msun at the time of explosion. Our non-rotating 32 Msun model
overestimates the derived radius of the progenitor, although this
could likely be reconciled with a fine-tuned model of a more massive
(between 40 and 50 Msun), hotter, and luminous progenitor. Our models
indicate a very uncertain ejecta mass of ~8 Msun, which is higher
than the average of the SN Ib ejecta mass that is derived from the
lightcurve (2-4 Msun). This possibly high ejecta mass could produce
detectable effects in the iPTF13bvn lightcurve and spectrum. If the
candidate is indeed confirmed to be the progenitor, our results
suggest that stars with relatively high initial masses (>30 Msun)
can produce visible SN explosions at their deaths and do not collapse
directly to a black hole.
Reference: Groh, Georgy and
Ekstrom 2013, A&A 558, 1
Status: Manuscript has been
accepted
Weblink:
http://arxiv.org/pdf/1307.8434.pdf
Comments:
Email: jose.groh@unige.ch
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M. Palate*, G. Rauw*, M. De
Becker*, Y. Nazé*, and P. Eenens²
*Institut
d'Astrophysique & Geophysique, Liege, Belgium
²Departamento
de Astronomia, Universidad de Guanajuato, Mexico
Context.
Massive-binary evolution models predict that some systems will go
through an evolutionary phase where the original primary has become a
supernova and left a compact object behind that then orbits a
Wolf-Rayet (hereafter, WR) star. WR 138 is an X-ray bright WR star
that has been described as a triple system, including a compact
companion in a short-period orbit.
Aims. Our goal is to search
for spectroscopic evidence of a compact companion around WR 138.
Methods. We used optical and X-ray spectra to search for
signatures of a compact companion, which can be revealed by
systematic variations in WR optical spectral lines induced by orbital
motion of the compact companion or by hard, luminous X-rays from
accretion onto this companion.
Results. The optical spectra
display emission-line profile variations that are most probably
caused by clumps inside the stellar winds. The radial velocities do
not vary on a short time-scale compatible with the suggested orbital
period of a putative compact companion. The X-ray spectra are found
to be normal for a WN5-6+OB system with no indication of accretion by
a compact companion.
Conclusions. There is no evidence for the
presence of a compact companion, and we therefore conclude that WR
138 is a normal long-period (P~1521 d) eccentric WR+OB
system.
Reference: Astronomy & Astrophysic
Status:
Manuscript has been accepted
Weblink:
Comments:
Email: matthieu.palate@doct.ulg.ac.be
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Th. Rivinius. A.C. Carciofi,
Ch. Martayan
ESO Chile, USP-IAG Brazil, ESO Chile
In
the past decade, a consensus has emerged regarding the nature of
classical Be stars: They are very rapidly rotating main sequence B
stars, which, through a still unknown, but increasingly constrained
process, form an outwardly diffusing gaseous, dust-free Keplerian
disk. In this work, first the definition of Be stars is contrasted to
similar classes, and common observables obtained for Be stars are
introduced and the respective formation mechanisms explained. We then
review the current state of knowledge concerning the central stars as
non-radially pulsating objects and non-magnetic stars, as far as it
concerns large scale, i.e., mostly dipolar, global fields. Localized,
weak magnetic fields remain possible, but are as of yet unproven. The
Be phenomenon, linked with one or more mass ejection processes, acts
on top of a rotation rate of about 75% of critical or above. The
properties of the process can be well constrained, leaving only few
options, most importantly, but not exclusively, non-radial pulsation
and small scale magnetic fields. Of these, it is well possible that
all are realized: In different stars, different processes may be
acting. Once the material has been lifted into Keplerian orbit,
memory of the details of the ejection process is lost, and the
material is governed by viscosity. The disks are fairly well
understood in the theoretical framework of the viscous decretion disk
model. This is not only true for the disk structure, but as well for
its variability, both cyclic and secular. Be binaries are reviewed
under the aspect of the various types of interactions a companion can
have with the circumstellar disk. Finally, extragalactic Be stars, at
lower metallicities, seem more common and more rapidly
rotating.
Reference: Astronomy and Astrophysics Review,
in press
Status: Manuscript has been accepted
Weblink:
http://arxiv.org/abs/1310.3962
Comments:
Email: triviniu@eso.org
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Skyler Grammer and Roberta M.
Humphreys
University of Minnesota
An increasing
number of non-terminal giant eruptions are being observed by modern
supernova and transient surveys. But very little is known about the
origin of these giant eruptions and their progenitors, many of which
are presumably very massive, evolved stars. Motivated by the small
number of progenitors positively associated with these giant
eruptions, we have begun a survey of the evolved massive star
populations in nearby galaxies. The nearby, nearly face on, giant
spiral M101 is an excellent laboratory for studying a large
population of very massive stars. In this paper, we present BVI
photometry obtained from archival HST/ACS WFC images of M101. We have
produced a catalog of luminous stars with photometric errors <10%
for V < 24.5 and 50% completeness down to V ~ 26.5 even in regions
of high stellar crowding. Using color and luminosity criteria we have
identified candidate luminous OB type stars and blue supergiants,
yellow supergiants, and red supergiants for future observation. We
examine their spatial distributions across the face of M101 and find
that the ratio of blue to red supergiants decreases by two orders of
magnitude over the radial extent of M101 corresponding to 0.5 dex in
metallicity. We discuss the resolved stellar content in the giant
star forming complexes NGC 5458, 5453, 5461, 5451, 5462, and 5449 and
discuss their color-magnitude diagrams in conjunction with the
spatial distribution of the stars to determine their spatio-temporal
formation histories.
Reference: AJ, 146, 114,
2013
Status: Manuscript has been accepted
Weblink:
Comments:
Email: roberta@umn.edu
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R. Blomme and D. Volpi
Royal
Observatory of Belgium, Ringlaan 3, B-1180 Brussel, Belgium
The
colliding winds in a massive binary system generate synchrotron
emission due to a fraction of electrons that have been accelerated to
relativistic speeds around the shocks in the colliding-wind region.
We studied the radio light curve of 9 Sgr = HD 164794, a massive
O-type binary with a 9.1-yr period. We investigated whether the radio
emission varies consistently with orbital phase and we determined
some parameters of the colliding-wind region. We reduced a large set
of archive data from the Very Large Array (VLA) to determine the
radio light curve of 9 Sgr at 2, 3.6, 6 and 20 cm. We also
constructed a simple model that solves the radiative transfer in the
colliding-wind region and both stellar winds. The 2-cm radio flux
shows clear phase-locked variability with the orbit. The behaviour at
other wavelengths is less clear, mainly due to a lack of observations
centred on 9 Sgr around periastron passage. The high fluxes and
nearly flat spectral shape of the radio emission show that
synchrotron radiation dominates the radio light curve at all orbital
phases. The model provides a good fit to the 2-cm observations,
allowing us to estimate that the brightness temperature of the
synchrotron radiation emitted in the colliding-wind region at 2 cm is
at least 4 x 10^8 K. The simple model used here already allows us to
derive important information about the colliding-wind region. We
propose that 9~Sgr is a good candidate for more detailed modelling,
as the colliding-wind region remains adiabatic during the whole orbit
thus simplifying the hydrodynamics.
Reference: AA,
accepted
Status: Manuscript has been accepted
Weblink:
http://arxiv.org/abs/1310.3997
Comments:
Email: Ronny.Blomme@oma.be
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G. Gräfener and J.S.
Vink
Armagh Observatory
Towards the end of their
evolution hot massive stars develop strong stellar winds and appear
as emission line stars, such as WR stars or LBVs. The quantitative
description of the mass loss in these important pre-SN phases is
hampered by unknowns such as clumping and porosity due to an
in-homogeneous wind structure, and by an incomplete theoretical
understanding of optically thick stellar winds. In this work we
investigate the conditions in deep atmospheric layers of WR stars to
find out whether these comply with the theory of optically thick
winds, and whether we find indications of clumping in these layers.
We use a new semi-empirical method to determine sonic-point optical
depths, densities, and temperatures for a large sample of WR stars of
the carbon (WC) and oxygen (WO) sequence. Based on an artificial
model sequence we investigate the reliability of our method and its
sensitivity to uncertainties in stellar parameters. We find that the
WR stars in our sample obey an approximate relation with
P_rad/P_gas~80 at the sonic point. This 'wind condition' is
ubiquitous for radiatively driven, optically thick winds, and sets
constraints on possible wind/envelope solutions affecting radii,
mass-loss rates, and clumping properties. Our results suggest that
the presence of an optically thick wind may force many stars near the
Eddington limit to develop clumped, radially extended sub-surface
zones. The clumping in these zones is most likely sustained by the
non-linear strange-mode instability, and may be the origin of the
observed wind clumping. The properties of typical late-type WC stars
comply with this model. Solutions without sub-surface clumping and
inflation are also possible but demand for compact stars with
comparatively low mass-loss rates. These objects may resemble the
small group of WO stars with their exceptionally hot stellar
temperatures and highly ionized winds.
Reference:
A&A
Status: Manuscript has been accepted
Weblink:
http://arxiv.org/abs/1309.6236
Comments:
Email: ggr@arm.ac.uk
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J.O. Sundqvist(1), S.
Simon-Diaz(2,3), J. Puls(1), and N. Markova(4)
1 -
University of Munich, Germany; 2 - Instituto de Astrofisica de
Canarias, Spain; 3 - Universidad de La Laguna, Spain; 4 - Institute
of Astronomy with NAO, Bulgaria
Context: Rotation plays a key
role in the life cycles of stars with masses above ~ 8 Msun. Hence,
accurate knowledge of the rotation rates of such massive stars is
critical for understanding their properties and for constraining
models of their evolution. Aims: This paper investigates the
reliability of current methods used to derive projected rotation
speeds v sin i from line-broadening signatures in the photospheric
spectra of massive stars, focusing on stars that are not rapidly
rotating. Methods: We use slowly rotating magnetic O-stars with
well-determined rotation periods to test the Fourier transform (FT)
and goodness-of-fit (GOF) methods typically used to infer projected
rotation rates of massive stars. Results: For our two magnetic test
stars with measured rotation periods longer than one year, i.e., with
v sin i < 1 km/s, we derive v sin i ~ 40-50 km/s from both the FT
and GOF methods. These severe overestimates are most likely caused by
an insufficient treatment of the competing broadening mechanisms
referred to as microturbulence and macroturbulence. Conclusions:
These findings warn us not to rely uncritically on results from
current standard techniques to derive projected rotation speeds of
massive stars in the presence of significant additional line
broadening, at least when v sin i <~ 50 km/s. This may, for
example, be crucial for i) determining the statistical distribution
of observed rotation rates of massive stars, ii) interpreting the
evolutionary status and spin-down histories of rotationally braked
B-supergiants, and iii) explaining the deficiency of observed O-stars
with spectroscopically inferred v sin i ~ 0 km/s. Further
investigations of potential shortcomings of the above techniques are
presently under way.
Reference: Accepted for
publication in A&A Letters. Pre-print on astro-ph
Status:
Manuscript has been accepted
Weblink:
http://adsabs.harvard.edu/abs/2013arXiv1310.4729S
Comments:
Email: mail@jonsundqvist.com
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Oskinova, L. M.; Steinke, M.;
Hamann, W.-R.; Sander, A.; Todt, H.; Liermann, A.
Potsdam
University, Germany
Very massive stars, 100 times heavier than
the sun, are rare. It is not yet known whether such stars can form in
isolation or only in star clusters. The answer to this question is of
fundamental importance. The central region of our Galaxy is ideal for
investigating very massive stars and clusters located in the same
environment. We used archival infrared images to investigate the
surroundings of apparently isolated massive stars presently known in
the Galactic Centre (GC). We find that two such isolated massive
stars display bow shocks and hence may be `runaways' from their
birthplace. Thus, some isolated massive stars in the GC region might
have been born in star clusters known in this region. However, no bow
shock is detected around the isolated star WR 102ka (Peony nebula
star), which is one of the most massive and luminous stars in the
Galaxy. This star is located at the centre of an associated
circumstellar nebula. To study whether a star cluster may be `hidden'
in the surroundings of WR 102ka, to obtain new and better spectra of
this star, and to measure its radial velocity, we obtained
observations with the integral-field spectrograph SINFONI at the
ESO's Very Large Telescope. Our observations confirm that WR 102ka is
one of the most massive stars in the Galaxy and reveal that this star
is not associated with a star cluster. We suggest that WR 102ka has
been born in relative isolation, outside of any massive star
cluster.
Reference: MNRAS
Status: Manuscript has
been accepted
Weblink: arXiv:1309.7651
Comments:
Email: lida@astro.physik.uni-potsdam.de
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F. Martins$^1$, A.
Palacios$^1$
1- LUPM, CNRS & Montpellier
University
In this paper, we compare the currently available
evolutionary tracks for Galactic massive stars. Our main goal is to
highlight the uncertainties on the predicted evolutionary paths. We
compute stellar evolution models with the codes MESA and STAREVOL. We
compare our results with those of four published grids of massive
stellar evolution models (Geneva, STERN, Padova and FRANEC codes). We
first investigate the effects of overshooting, mass loss,
metallicity, chemical composition. We subsequently focus on rotation.
Finally, we compare the predictions of published evolutionary models
with the observed properties of a large sample of Galactic stars. We
find that all models agree well for the main sequence evolution.
Large differences in luminosity and temperatures appear for the post
main sequence evolution, especially in the cool part of the HR
diagram. Depending on the physical ingredients, tracks of different
initial masses can overlap, rendering any mass estimate doubtful. For
masses between 7 and 20 Msun, we find that the main sequence width is
slightly too narrow in the Geneva models including rotation. It is
(much) too wide for the (STERN) FRANEC models. This conclusion is
reached from the investigation of the HR diagram and from the
evolution of the surface velocity as a function of surface gravity.
An overshooting parameter alpha between 0.1 and 0.2 in models with
rotation is preferred to reproduce the main sequence width.
Determinations of surface abundances of carbon and nitrogen are
partly inconsistent and cannot be used at present to discriminate
between the predictions of published tracks. For stars with initial
masses larger than about 60 Msun, the FRANEC models with rotation can
reproduce the observations of luminous O supergiants and WNh stars,
while the Geneva models remain too hot.
Reference: A&A
accepted
Status: Manuscript has been accepted
Weblink:
http://arxiv.org/abs/1310.7218
Comments:
Email: fabrice.martins@univ-montp2.fr
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Jose H. Groh (1), Georges Meynet
(1), Cyril Georgy (2), and Sylvia Ekstrom (1)
(1) Geneva
Observatory, Switzerland
(2) Keele University, UK
We
investigate the fundamental properties of core-collapse supernova
(SN) progenitors from single stars at solar metallicity. For this
purpose, we combine Geneva stellar evolutionary models with initial
masses of Mini = 20-120 Msun with atmospheric and wind models using
the radiative transfer code CMFGEN. We provide synthetic photometry
and high-resolution spectra of hot stars at the pre-SN stage. For
models with Mini = 9-20 Msun, we supplement our analysis using
publicly available MARCS model atmospheres of RSGs to estimate their
synthetic photometry. We employ well-established observational
criteria of spectroscopic classification and find that, depending on
their initial mass and rotation, massive stars end their lives as red
supergiants (RSG), yellow hypergiants (YHG), luminous blue variables
(LBV), and Wolf-Rayet (WR) stars of the WN and WO spectral types. For
rotating models, we obtained the following types of SN progenitors:
WO1-3 (Mini ≥ 32 Msun), WN10-11 (25 < Mini < 32 Msun), LBV
(20 ≤ Mini ≤ 25 Msun), G1 Ia+ (18 < Mini < 20 Msun), and
RSGs (9 ≤ Mini ≤ 18 Msun). For non-rotating models, we found
spectral types WO1-3 (Mini > 40 Msun), WN7-8 (25 < Mini ≤ 40
Msun), WN11h/LBV (20 < Mini ≤ 25 Msun), and RSGs (9 ≤ Mini ≤
20 Msun). Our rotating models indicate that SN IIP progenitors are
all RSG, SN IIL/b progenitors are 56% LBVs and 44% YHGs, SN Ib
progenitors are 96% WN10-11 and 4% WOs, and SN Ic progenitors are all
WO stars. We find that the most massive and luminous SN progenitors
are not necessarily the brightest ones in a given filter, since this
depends on their luminosity, temperature, wind density, and the way
the spectral energy distribution compares to a filter bandpass. We
find that SN IIP progenitors (RSGs) are bright in the RIJHKS filters
and faint in the UB filters. SN IIL/b progenitors (LBVs and YHGs),
and SN Ib progenitors (WNs) are relatively bright in optical/infrared
filters, while SN Ic progenitors (WOs) are faint in all optical
filters. We argue that SN Ib and Ic progenitors from single stars
should be undetectable in the available pre-explosion images with the
current magnitude limits, in agreement with observational
results.
Reference: Groh, Meynet, Georgy and Ekstrom
2013, A&A 558, 131
Status: Manuscript has been
accepted
Weblink:
http://arxiv.org/abs/arXiv:1308.4681
Comments:
Email: jose.groh@unige.ch
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C. Sabín-Sanjulián(1,2), S.
Simón-Díaz(1,2), A. Herrero(1,2), N. R. Walborn(3), J. Puls(4), J.
Maíz Apellániz(5), C. J. Evans(6), I. Brott(7), A. de Koter(8,9),
M. Garcia(10), N. Markova(11), F. Najarro(10), O. H.
Ramírez-Agudelo(8), H. Sana(3), W. D. Taylor(6) and J. S.
Vink(12)
1- Instituto de Astrofísica de Canarias, E-38200
La Laguna, Tenerife, Spain
2- Departamento de Astrofísica,
Universidad de La Laguna, E-38205 La Laguna, Tenerife, Spain
3-
Space Telescope Science Institute, 3700 San Martin Drive, Baltimore,
MD 21218, USA
4- Universit"ats-Sternwarte, Scheinerstrasse
1, 81679 Munchen, Germany
5- Instituto de Astrofísica de
Andalucía-CSIC, Glorieta de la Astronom'ia s/n, E-18008 Granada,
Spain
6- UK Astronomy Technology Centre, Royal Observatory
Edinburgh, Blackford Hill, Edinburgh, EH9 3HJ, UK
7- University
of Vienna, Department of Astrophysics, Turkenschanzstr. 17, 1180,
Vienna, Austria
8- Astronomical Institute Anton Pannekoek,
University of Amsterdam, Kruislaan 403, 1098 SJ, Amsterdam, The
etherlands
9- Instituut voor Sterrenkunde, Universiteit Leuven,
Celestijnenlaan 200 D, 3001, Leuven, Belgium
10- Centro de
Astrobiología (CSIC-INTA), Ctra. de Torrejón a Ajalvir km-4,
E-28850 Torrejón de Ardoz, Madrid, Spain
11- Institute of
Astronomy with NAO, Bulgarian Academy of Sciences, PO Box 136, 4700
Smoljan, Bulgaria
12- Armagh Observatory, College Hill, Armagh,
BT61 9DG, Northern Ireland, UK
Context. OV z stars, a subclass
of O-type dwarfs characterized by having HeII4686 stronger in
absorption than any other helium line in their blue-violet spectra,
have been suggested o be on or near the Zero-Age-Main-Sequence
(ZAMS). If their youth were confirmed, they would be key objects with
which to advance our knowledge of the physical properties of massive
stars in the early stages of their lives.
Aims. To test the
hypothesis of OV z stars being at a different (younger) evolutionary
stage in comparison with normal O-type dwarfs.
Methods. We
perform the first comprehensive quantitative spectroscopic analysis
of a statistically-meaningful sample of OV z and OV stars in the same
star-forming region, exploiting the large number of OV z stars
identified by the VLT-FLAMES Tarantula Survey in the 30 Doradus
region of the Large Magellanic Cloud (LMC). We obtain the stellar and
wind parameters of 38 OV z stars (and a control sample of 46 OV
stars) using the FASTWIND stellar atmosphere code and the IACOB-GBAT,
a grid-based tool developed for automated quantitative analysis of
optical spectra of O stars. In the frame of a differential study, we
compare the physical and evolutionary properties of both samples,
locating the stars in the logg vs. logT_eff, logQ vs. logT_eff, and
logL/L_sun vs. logT_eff diagrams. We also investigate the predictions
of the FASTWIND code regarding the O,V z phenomenon.
Results.
We find a differential distribution of objects in terms of effective
temperature, with OV z stars dominant at intermediate values. The OV
z stars in 30,Doradus tend to be younger (i.e. closer to the ZAMS),
less luminous, and have weaker winds than the OV stars, but we also
find examples with ages of 2-4 Myr, and with luminosities and winds
which are similar to those of normal O dwarfs. Moreover, the OV z
stars do not appear to have higher gravities than the OV stars.
In
addition to effective temperature and wind strength, our FASTWIND
predictions indicate the importance of taking other stellar
parameters (gravity and projected rotational velocity) into account
for the correct interpretation of the OV z phenomenon.
Conclusions.
In general, the OV z stars appear to be on, or very close to, the
ZAMS, but there are some examples where the Vz classification does
not necessarily imply extreme youth. In particular, the presence of
OV z stars in our sample at more evolved phases than expected is
likely a consequence of modest O-star winds due to the
low-metallicity environment of the LMC.
Reference:
AA/2013/22798
Status: Manuscript has been submitted
Weblink:
Comments:
Email: cssj@iac.es
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O.H. Ram'irez-Agudelo$^1$, S.
Sim'on-D'{i}az $^{2,3}$, H. Sana$^{1,4}$, A. de Koter$^{1,5}$, C.
Sab'{i}n-Sanjul'{i}an$^{2,3}$, S.E. de Mink$^{6,7}$, P. L.
Dufton$^{8}$, G. Gr"afener$^{9}$, C.J. Evans$^{10}$, A.
Herrero$^{2,3}$, N. Langer$^{11}$, D.J. Lennon$^{12}$, J. Ma'{i}z
Apell'aniz$^{13}$, N. Markova$^{14}$, F. Najarro$^{15}$, J.
Puls$^{16}$, W.D. Taylor$^{10}$, and
J.S. Vink$^{9}$
$^{1}$
Astronomical Institute Anton Pannekoek, University of Amsterdam, The
Netherlands
$^{2}$ Instituto de Astrof'{i}sica de Canarias, C/
V'{i}a L'{a}ctea s/n, E-38200 La Laguna, Tenerife, Spain
$^{3}$
Departamento de Astrof'{i}sica, Universidad de La Laguna, Avda.
Astrof'{i}sico Francisco S'{a}nchez s/n, E-38071 La Laguna, Tenerife,
Spain
$^{4}$ Space Telescope Science Institute, 3700 San Martin
Drive, Baltimore, MD 21218, USA
$^{5}$ Instituut voor
Sterrenkunde, Universiteit Leuven, Celestijnenlaan 200 D, 3001,
Leuven, Belgium
$^{6}$ Observatories of the Carnegie Institution
for Science, 813 Santa Barbara St, Pasadena, CA 91101, USA
$^{7}$
Cahill Center for Astrophysics, California Institute of Technology,
Pasadena, CA 91125, USA
$^{8}$ Astrophysics Research Centre,
School of Mathematics and Physics, Queen's University of Belfast,
Belfast BT7 1NN, UK
$^{9}$ Armagh Observatory, College Hill,
Armagh, BT61 9DG, Northern Ireland, UK
$^{10}$ UK Astronomy
Technology Centre, Royal Observatory Edinburgh, Blackford Hill,
Edinburgh, EH9 3HJ, UK
$^{11}$ Argelander-Institut f"ur
Astronomie, Universit"at Bonn, Auf dem H"ugel 71, 53121
Bonn, Germany
$^{12}$ European Space Astronomy Centre (ESAC),
Camino bajo del Castillo, s/n Urbanizacion Villafranca del Castillo,
Villanueva de la Ca~nada, E-28692 Madrid, Spain
$^{13}$ Instituto
de Astrof'{i}sica de Andaluc'{i}a-CSIC, Glorieta de la Astronom'ia
s/n E-18008 Granada, Spain
$^{14}$ Institute of Astronomy with
NAO, Bulgarian Academy of Science, PO Box 136, 4700 Smoljan, Bulgaria
$^{15}$ Centro de Astrobiolog'{i}a (CSIC-INTA), Ctra. de
Torrej'on a Ajalvir km-4, E-28850 Torrej'on de Ardoz, Madrid, Spain
$^{16}$ Universit"atssternwarte Scheinerstrasse 1, 81679
M"unchen, Germany
The 30 Doradus (30,Dor) region in the
Large Magellanic Cloud (also known as the Tarantula Nebula) is the
nearest massive starburst region, containing the richest sample of
massive stars in the Local Group. It is the best possible
laboratory to investigate aspects of the formation and evolution of
massive stars. Here, we focus on rotation which is a key parameter in
the evolution of these objects. We establish the projected rotational
velocity, $v_{e}sin i$, distribution of an unprecedented sample of
216 radial
velocity constant ($rm{Delta RV, leq, 20 ,km s^{-1}}$)
O-type stars in 30,Dor observed in the framework of the VLT-FLAMES
Tarantula Survey (VFTS). The distribution of $v_{e}sin i$ shows a
two-component structure: a peak around 80 $rm{km s^{-1}}$ and a
high-velocity tail extending up to $sim$600 $rm{km s^{-1}}$. Around
75% of the sample has 0 $leq, v_{e}sin i leq$ 200 $rm{km s^{-1}}$
with the other 25% distributed in the high-velocity tail.
The
presence of the low-velocity peak is consistent with that found in
other studies of late-O and early-B stars.
The high-velocity tail
is compatible with expectations from binary interaction synthesis
models and may be predominantly populated by post-binary interaction,
spun-up, objects and mergers. This may have important implications
for the nature of progenitors of long-duration gamma ray
bursts.
Reference: Conference proceedings article:
Massive stars: from alpha to Omega, 10-14 June 2013, Rhodes,
Greece
Status: Conference proceedings
Weblink:
http://adsabs.harvard.edu/abs/2013arXiv1309.2929R
Comments:
Email: o.h.ramirezagudelo@uva.nl
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Prof. Artemio Herrero
Instituto
de Astrofisica de Canarias
C/ Via Lactea s/n
E-38205 La
Laguna
Spain
The Instituto de Astrofísica de Canarias
(IAC, Tenerife, Spain) invites applications for ONE postdoctoral
contract in Astrophysics to work within the framework of the project
“Formation And Evolution Of Massive Stars Across The Milky Way And
The Local Group” (AYA2012-39364-C02-01), financed by the Spanish
Ministry of Economy and Competitiveness and and led by Prof. Artemio
Herrero Davó.
The IAC is a leading Center for Astrophysics
in Spain, covering theoretical and observational research and
instrumentation across most areas of Astrophysics. It has been
selected as a “Severo Ochoa Centers of Excellence” in research by
the Spanish Government. The successful candidate will have access to
all telescopic and supercomputing facilities in the Canary Islands,
including the 10.4m GTC. Ample travel funding is available.
The
candidate will join the research currently underway in the group:
multi-wavelength observations and analysis of massive stars in the
Milky Way and nearby galaxies, comparison with evolutionary models,
update of atmosphere models, velocity fields.
The candidate
should hold a PhD in Astrophysics. High value will be given to
experience in any of the following fields: observational astronomy,
analysis of stellar spectra and pulsations, use of atmosphere or
evolutionary models and knowledge of numerical and statistical
techniques.
Remuneration: The gross annual salary is 32.886 €
Duration: Until the end of the 2015.
The application
procedure is explained on the web site. All documents, including the
recommendation letters, must be received before the application
deadline: October 31, 2013.
Details of the selection process,
including the list of applicants, will be published on the web;
successful candidates will also be informed by
e-mail.
Attention/Comments: interested candidates may
contact Artemio Herrero at the emailaddress below
Weblink:
http://www.iac.es/info.php?op1=26&id=446〈=en
Email:
ahd@iac.es
Deadline: October 31th, 2013
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6-11 July 2014
Venue:
Toulouse, France
This is the first announcement for CoRoT
Symposium 3, Kepler KASC-7 joint meeting entitled The Space
Photometry Revolution. The conference will be held in Toulouse
(France), 6-11 July 2014.
Preregistration is now open!
Topics
include:
1. Extrasolar planets and planet systems
2. Probing
stellar structure and evolution with asteroseismology
3. Binarity
and star-planet interactions
4. Stellar activity and rotation
5.
Present and future ground-based and space projects. Synergies
Important dates:
* Preregistration opens: 20 Sep 2013
*
Registration opens: 15 Dec 2013
* Deadline for early
registration: 01 Mar 2014
* Abstract deadline for contributed
talks: 31 Mar 2014
* Abstract deadline for posters: 15 May 2014
* Deadline for registration and payment: 15 May 2014
We
invite you to express your interest by sending an e-mail to
corot3-kasc7@sciencesconf.org
Weblink:
http://corot3-kasc7.sciencesconf.org/
Email:
jerome.ballot@irap.omp.eu
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Ted Gull
NASA/GSFC
Eta Carina will
undergo its next periastron event in July-August 2014. This
coordination meeting will focus on current observations, models of
the massive binary system, and observations needed to constrain the
models.
We encourage you to contact Ted.Gull@nasa.gov if you
plan to attend, along with potential contributions and subjects that
you would like to discuss. A head count is desired by October 31.
A
similar planning session at Mt. Rainier in the summer of 2002 focused
on the Hubble Eta Carinae Treasury Program. The inputs of several
dozen astronomers at that meeting strongly impacted the actual
observations, brought in additional coordinated observations and
inspired new approaches to the modeling of the massive interacting
winds. It is our goal to further improve our knowledge of this
fascinating astrophysical laboratory with a coordinated approach.
This meeting was initially planned to be splinter sessions
within the American Astronomical Society January 2014 meeting.
However, due to cost, scheduling conflicts and potential limiting
quotas of NASA attendees, we chose to move the coordination meeting
to a separate venue. A conference room has been found at University
of Maryland, Baltimore County for the two-day meeting. Within the
building complex are located other meeting rooms and a cafeteria. The
facility is about six miles from Baltimore Washington International
Airport and just off Interstates 95 and 195.
The format of
the meeting, based upon many local meetings discussing Eta Carinae,
will be a series of reviews with structured discussions on these
general topics:
Current observations
Current models of
massive stars
Observations needed to constrain models that could
be obtained across the 2014.6 periastron event.
Models needed to
explain current and planned observations.
Small group
meetings addressing specific topics will be encouraged both
afternoons.
A draft agenda will be circulated in early
November.
Additional information will be posted as it comes
available on: http://etacar2014.wikidot.com/meetings
Reference:
Notice of meeting
Status: Other
Weblink:
Comments:
Email: Ted.Gull@nasa.gov
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