ISSN 1783-3426
|
Next Massive Star Meeting
A
Spectroscopic Campaign on WR 134, WR135, and WR 137
European
Ultraviolet Visible Observatory
The
Advanced Telescope for High Energy Astrophysics
Evolution of blue supergiants and alpha
Cygni variables; Puzzling CNO surface abundances
Single-Star
HII Regions as a Probe of Massive Star Spectral
Turbulent
Entrainment at the Boundaries of the Convective Cores of
Main-sequence Stars
The distance to
the young open cluster Westerlund 2
X-ray
properties of the young open clusters HM1 and IC2944/2948
Luminous
and Variable Stars in M31 and M33. I. The Warm Hypergiants and
Post-Red Supergiant Evolution
Constraints
on porosity and mass loss in O-star winds from modeling of X-ray
On
magnetic inhibition of photospheric macro turbulence generated in the
iron-bump opacity zone of O-stars
On
the simultaneous evolution of massive protostars and their host
cores
Unexpected Ionization
Structure in Eta Carinae's ``Weigelt Knots''
HD45314:
a new gamma Cas analog among Oe stars
Advanced
burning stages and fate of 8-10 Mo stars
Strange mode instability for
micro-variations in Luminous Blue Variables
The
Galactic O-Star Spectroscopic Catalog (GOSC) and Survey (GOSSS):
first whole-sky results and further updates
Eta Carinae Splinter session at 223rd AAS Meeting January 2014, Washington, DC, USA
Post-doctoral or PhD position in
stellar astrophysics
Postdoctoral
Research Fellow
Numerical Modelling
of Stellar Interiors
Giants of
Eclipse
IAUS 302 - Full program and
registration deadline
Dear colleagues,
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
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We are announcing that the
large "Pro-Am" campaign to spectroscopically study the
variability in 3 WR stars will start on May 17, continuing through
September 17 of this year. We have received several telescope
allocations, including a 4-month span at the IAC 0.8m (with only a
few nights devoted to other projects) and a few allocations of a few
weeks. A team of amateur spectroscopists will be observing both at
the IAC as well as their small telscopes to study the CIRs and clumps
in these stars to create a long, intense time-series. We welcome
additional contributors if you have the availability and telescope
time.
Weblink: http://www.stsci.de/wr134/index.htm
Email:
richardson@astro.umontreal.ca
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In response to the recent ESA call for science themes for large
missions, the UV astrophysics community has submitted a white paper
(http://www.nuva.eu/whitepaper/files/euvo_wp_220513_fin.pdf) to
promote a mission for a visible-UV observatory. Several areas of
astrophysics are interested in UV observations, in particular massive
stars. EUVO will provide access to key diagnostics of stellar
properties, stellar winds, and star-ISM interactions. The EUVO team
invites you to become a supporter of this project :
http://www.nuva.eu/whitepaper/supporters.php
Weblink:
http://www.nuva.eu/whitepaper/index.php
Email:
Coralie.Neiner@obspm.fr
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In response to the recent ESA call for
science themes to define its future large missions, the X-ray
astrophysics community has submitted a white paper
(http://arxiv.org/abs/1306.2307) to promote the Advanced Telescope
for High Energy Astrophysics (Athena+) mission. Athena+ provides the
necessary performance (e.g. angular resolution, spectral resolution,
survey grasp) to address a number of fundamental questions in modern
astrophysics and revolutionize our understanding of the Hot and
Energetic Universe. These capabilities will provide a powerful
observatory to be used in all areas of astrophysics as illustrated by
a series of
supporting papers, including one on star formation
and evolution (http://arxiv.org/abs/1306.2333). In the field of
massive stars, Athena+ will not only allow us to study many more
objects with an unprecedented spectral resolution, but will also
pioneer the study of the dynamics of
their X-ray emission via
time-resolved high-resolution spectroscopy. In this way, Athena+ will
be a unique tool to study small and large-scale structures in the
winds of single massive stars, wind interactions in
massive
binary systems, and many other topics. The Athena+ Science Working
Group invites you to become a supporter of this project. You can do
so by signing up at
http://fs6.formsite.com/ATHENA2028/form2/index.html
Weblink:
http://www.the-athena-x-ray-observatory.eu/
Email:
rauw@astro.ulg.ac.be
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Hideyuki Saio$^1$, Cyril
Georgy$^2$, and Georges Meynet$^3$
1 - Astronomical
Institute, Tohoku University, 2 - Astrophysics, Lennard-Jones
Laboratories, EPSAM, Keele, University, 3 - Geneva Observatory,
University of Geneva
A massive star can enter the blue
supergiant region either evolving directly from the main-sequence, or
evolving from a previous red supergiant stage. The fractions of the
blue supergiants having different histories depend on the internal
mixing and mass-loss during the red supergiant stage. We study the
possibility to use diagnostics based on stellar pulsation to
discriminate blue supergiants having different evolution histories.
For this purpose we have studied the pulsation property of massive
star models calculated with the Geneva stellar evolution code for
initial masses ranging from 8 to 50 M_odot with a solar metallicity
of Z=0.014. We have found that radial pulsations are excited in the
blue-supergiant region only in the models that had been
red-supergiants before. This would provide us with a useful mean to
diagnose the history of evolution of each blue-supergiant. At a given
effective temperature, much more nonradial pulsations are excited in
the model after the red-supergiant stage than in the model evolving
towards the red-supergiant. The properties of radial and nonradial
pulsations in blue supergiants are discussed. Predicted periods are
compared with period ranges observed in some alpha-Cygni variables in
the Galaxy and NGC 300. We have found that blue supergiant models
after the red- supergiant stage roughly agree with observed period
ranges in most cases. However, we are left with the puzzle that the
predicted surface N/C and N/O ratios seem to be too high compared
with those of Deneb and Rigel.
Reference: MNRAS in
press
Status: Manuscript has been accepted
Weblink:
http://arxiv.org/abs/1305.2474
Comments:
Email: saio@astr.tohoku.ac.jp
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J. Zastrow(1), M.S. Oey(1),
E.W. Pellegrini(2)
(1) U. Michigan; (2) U. Toledo
The
shape of the OB-star spectral energy distribution is a critical
component in many diagnostics of the ISM and galaxy properties. We
use single-star HII regions from the LMC to quantitatively examine
the ionizing SEDs from widely available CoStar, TLUSTY, and WM-basic
atmosphere grids. We evaluate the stellar atmosphere models by
matching the emission-line spectra that they predict from CLOUDY
photoionization simulations with those observed from the nebulae. The
atmosphere models are able to reproduce the observed optical nebular
line ratios, except at the highest energy transitions > 40 eV,
assuming that the gas distribution is non-uniform. Overall we find
that simulations using WM-basic produce the best agreement with the
observed line ratios. The rate of ionizing photons produced by the
model SEDs is consistent with the rate derived from the Halpha
luminosity for standard, log(g) = 4.0 models adopted from the
atmosphere grids. However, there is a systematic offset between the
rate of ionizing photons from different atmosphere models that is
correlated with the relative hardness of the SEDs. In general
WM-basic and TLUSTY atmosphere models predict similar effective
temperatures, while CoStar predicts effective temperatures that are
cooler by a few thousand degrees. We compare our effective
temperatures, which depend on the nebular ionization balance, to
conventional photospheric-based calibrations from the literature. We
suggest that in the future, spectral type to effective temperature
calibrations can be constructed from nebular data.
Reference:
ApJ, 769, 94
Status: Manuscript has been accepted
Weblink:
http://iopscience.iop.org/0004-637X/769/2/94/
Email:
jazast@umich.edu
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E.I. Staritsin
K.A.
Barkhatova Kourovka Astronomical Observatory, B.N. El’tsin Ural
Federal University, Ekaterinburg, Russia
Extra mixing of
matter in stellar interiors at the boundaries of the convective cores
of main sequence stars is considered for the first time using the
physical model of turbulent entrainment developed by Arnett and
collaborators based on three-dimensional hydrodynamical simulations.
The model takes into account the energy that goes into mixing the
matter of the convective core and layers stable against convection
located above the core. It is shown that the extent of the region of
extra mixing expressed in units of the pressure scale height is not
constant, and decreases as the star evolves along the main sequence.
Adequate allowance for extra mixing at the boundaries of convective
cores is necessary to clarify the relative importance of different
mixing mechanisms in stellar interiors, as well as to determine
stellar parameters using asteroseismology.
Reference:
Astronomy Reports, Vol. 57
Status: Manuscript has been
accepted
Weblink:
Comments:
Email:
Eugenij.Staritsin@usu.ru
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G. Carraro$^1$, D.
Turner$^2$, D. Majaess$^2$, G. Baume$^3$
1 - ESO, Alonso
de Cordova 3107, 19001, Santiago de Chile, Chile; 2 - Department of
Astronomy and Physics, Saint Mary’s University, Halifax, NS B3H
3C3, Canada; 3 - Facultad de Ciencias Astron´omicas y Geofisicas
(UNLP), Instituto de Astrofisica de La Plata (CONICETUNLP), Paseo del
Bosque s/n, La Plata, Argentina
A new X-ray, {it UBVR}$I_c$,
and {it JHK$s$} study of the young cluster Westerlund 2 was
undertaken to resolve discrepancies tied to the cluster's distance.
Existing spectroscopic observations for bright cluster members and
new multi-band photometry imply a reddening relation towards
Westerlund~2 described by $E_{U-B}/E_{B-V}=0.63 + 0.02;E_{B-V}$.
Variable-extinction analyses for Westerlund~2 and nearby IC 2581
based upon spectroscopic distance moduli and ZAMS fitting yield
values of $R_V=A_V/E_{B-V}=3.88pm0.18$ and $3.77pm0.19$,
respectively, and confirm prior assertions that anomalous
interstellar extinction is widespread throughout Carina (e.g., Turner
2012). The results were confirmed by applying the color difference
method to {it UBVR$I_c$JH$K_s$} data for 19
spectroscopically-observed cluster members, yielding
$R_V=3.85pm0.07$. The derived distance to Westerlund~2 of
$d=2.85pm0.43$ kpc places the cluster on the far side of the Carina
spiral arm. The cluster's age is no more than $tau sim2times10^6$ yr
as inferred from the cluster's brightest stars and an X-ray (Chandra)
cleaned analysis of its pre-main-sequence demographic. Four
Wolf-Rayet stars in the cluster core and surrounding corona (WR20a,
WR20b, WR20c, and WR20aa) are likely cluster members, and their
inferred luminosities are consistent with those of other late-WN
stars in open clusters. The color-magnitude diagram for Westerlund~2
also displays a gap at spectral type B0.5 V with associated color
spread at higher and lower absolute magnitudes that might be linked
to close binary mergers. Such features, in conjunction with the
evidence for mass loss from the WR stars, may help to explain the
high flux of $gamma$ rays, cosmic rays, and X-rays from the direction
towards Westerlund~2.
Reference: A&A, in
press
Status: Manuscript has been accepted
Weblink:
http://arxiv.org/abs/1305.4309
Comments:
Email: gcarraro@eso.org
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Yael Naze, Gregor Rauw,
Hugues Sana, Michael F. Corcoran
ULg, ULg, Univ.
Amsterdam, GSFC
Using XMM data, we study for the first time
the X-ray emission of HM1 and IC2944/2948. Low-mass,
pre-main-sequence objects with an age of a few Myr are detected, as
well as a few background or foreground objects. Most massive stars in
both clusters display the usual high-energy properties of that type
of objects, though with log(Lx/Lbol) apparently lower in HM1 than in
IC2944/2948. Compared with studies of other clusters, it seems that a
low signal-to-noise ratio at soft energies, due to the high
extinction, may be the main cause of this difference. In HM1, the two
Wolf-Rayet stars show contrasting behaviors: WR89 is extremely
bright, but much softer than WR87. It remains to be seen whether
wind-wind collisions or magnetically confined winds can explain these
emissions. In IC2944/2948, the X-ray sources concentrate around
HD101205; a group of massive stars to the north of this object is
isolated, suggesting that there exist two subclusters in the
field-of-view.
Reference: accepted by A&A
Status:
Manuscript has been accepted
Weblink:
http://arxiv.org/abs/1305.5105
Email:
naze@astro.ulg.ac.be
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Roberta M. Humphreys^1, Kris
Davidson^1,
Skyler Grammer^1, Nathan Kneeland^1,
John C.
Martin^2, Kerstin Weis^3 and Birgitta Burggraf^3
1.
University of Minnesota
2. University of Illinois, Springfield
3. Astronomical Institute, Ruhr-Universitaet Bochum, Germany
The
progenitors of Type IIP supernovae have an apparent upper limit to
their initial masses of about 20 solar masses, suggesting that the
most massive red supergiants evolve to warmer temperatures before
their terminal explosion. But very few post-red supergiants are
known. We have identified a small group of luminous stars in M31 and
M33 that are candidates for post-red supergiant evolution. These
stars have A -- F-type supergiant absorption line spectra and strong
hydrogen emission. Their spectra are also distinguished by the Ca II
triplet and [Ca II] doublet in emission formed in a low density
circumstellar environment. They all have significant near- and
mid-infrared excess radiation due to free-free emission and thermal
emission from dust. We estimate the amount of mass they have shed and
discuss their wind parameters and mass loss rates which range from a
few times 10^-6 to 10^-4 solar masses/yr.. On an HR Diagram, these
stars will overlap the region of the LBVs at maximum light, however
the warm hypergiants are not LBVs. Their non-spherical winds are not
optically thick and they have not exhibited any significant
variability. We suggest, however, that the warm hypergiants may be
the progenitors of the ``less luminous'' LBVs such as R71 and even
SN1987A.
Reference: Astrophysical Journal
Status:
Manuscript has been accepted
Weblink:
Comments:
Email: roberta@umn.edu
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Maurice A. Leutenegger$^{1,2}$, David H. Cohen$^3$, Jon O.
Sundqvist$^{4,5}$, Stanley P. Owocki$^4$
1 - CRESST and
X-ray Astrophysics Laboratory
NASA/Goddard Space Flight Center;
2 - Department of Physics, University of Maryland, Baltimore
County;
3 - Department of Physics and Astronomy, Swarthmore
College;
4 - Bartol Research Institute, University of Delaware;
5 - Universitaetssternwarte Muenchen
We fit X-ray emission line
profiles in high resolution XMM-Newton and Chandra grating spectra of
the early O supergiant Zeta Pup with models that include the effects
of porosity in the stellar wind. We explore the effects of porosity
due to both spherical and flattened clumps. We find that porosity
models with flattened clumps oriented parallel to the photosphere
provide poor fits to observed line shapes. However, porosity models
with isotropic clumps can provide acceptable fits to observed line
shapes, but only if the porosity effect is moderate. We quantify the
degeneracy between porosity effects from isotropic clumps and the
mass-loss rate inferred from the X-ray line shapes, and we show that
only modest increases in the mass-loss rate (<~ 40%) are allowed
if moderate porosity effects (h_infty <~ R_*) are assumed to be
important. Large porosity lengths, and thus strong porosity effects,
are ruled out regardless of assumptions about clump shape. Thus,
X-ray mass-loss rate estimates are relatively insensitive to both
optically thin and optically thick clumping. This supports the use of
X-ray spectroscopy as a mass-loss rate calibration for bright, nearby
O stars.
Reference: 2013 ApJ, 770, 80
Status:
Manuscript has been accepted
Weblink:
http://iopscience.iop.org/0004-637X/770/1/80/
Comments:
Preprint available at
http://arxiv.org/abs/1305.5595
Email:
maurice.a.leutenegger@nasa.gov
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J.O. Sundqvist(1,2), V.
Petit(2), S.P. Owocki(2), G.A. Wade(3), J. Puls(1), the MiMeS
Collaboration
1 - University of Munich
2 - University
of Delaware
3 - RMC, Kingston
Massive, hot OB-stars show
clear evidence of strong macroscopic broadening (in addition to
rotation) in their photospheric spectral lines. This paper examines
the occurrence of such ``macro-turbulence'' in slowly rotating
O-stars with strong, organised surface magnetic fields. Focusing on
the CIV 5811A line, we find evidence for significant macro-turbulent
broadening in all stars except NGC1624-2, which also has (by far) the
strongest magnetic field. Instead, the very sharp CIV lines in
NGC1624-2 are dominated by magnetic Zeeman broadening, from which we
estimate a dipolar field 20 kG. By contrast, magnetic broadening is
negligible in the other stars (due to their weaker field strengths,
on the order of 1 kG), and their CIV profiles are typically very
broad and similar to corresponding lines observed in non-magnetic
O-stars. Quantifying this by an isotropic, Gaussian macro-turbulence,
we derive vmac 2.2 (+- 0.9/2.2) km/s for NGC-1624, and vmac = 20-65
km/s for the rest of the magnetic sample. We use these observational
results to test the hypothesis that the field can stabilise the
atmosphere and suppress the generation of macro-turbulence down to
stellar layers where the magnetic pressure PB and the gas pressure Pg
are comparable. Using a simple grey atmosphere to estimate the
temperature T0 at which PB = Pg, we find that T0 > Teff for all
investigated magnetic stars, but that T0 reaches the layers
associated with the iron opacity-bump in hot stars only for
NGC1624-2. This is consistent with the view that the responsible
physical mechanism for photospheric O-star macro-turbulence may be
stellar gravity-mode oscillations excited by sub-surface convection
zones, and suggests that a sufficiently strong magnetic field can
suppress such iron-bump generated convection and associated
pulsational excitation.
Reference: Accepted for
publication in MNRAS, pre-print on astro-ph
Status: Manuscript has
been accepted
Weblink:
http://arxiv.org/abs/1305.5549
Comments:
Email: mail@jonsundqvist.com
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Rolf Kuiper & Harold W. Yorke
Jet Propulsion
Laboratory, California Institute of Technology, 4800 Oak Grove Drive,
Pasadena, CA 91109, USA
Studies of the evolution of massive
protostars and the evolution of their host molecular cloud cores are
commonly treated as separate problems. However, interdependencies
between the two can be significant. Here, we study the simultaneous
evolution of massive protostars and their host molecular cores using
a multi-dimensional radiation hydrodynamics code that incorporates
the effects of the thermal pressure and radiative acceleration
feedback of the centrally forming protostar. The evolution of the
massive protostar is computed simultaneously using the stellar
evolution code STELLAR, modified to include the effects of variable
accretion. The interdependencies are studied in three different
collapse scenarios. For comparison, stellar evolutionary tracks at
constant accretion rates and the evolution of the host cores using
pre-computed stellar evolutionary tracks are computed.
The
resulting interdependencies of the protostellar evolution and the
evolution of the environment are extremely diverse and depend on the
order of events, in particular the time of circumstellar accretion
disk formation with respect to the onset of the bloating phase of the
star. Feedback mechanisms affect the instantaneous accretion rate and
the protostar’s radius, temperature and luminosity on timescales
equal or smaller than 5 kyr, corresponding to the accretion timescale
and Kelvin-Helmholtz contraction timescale, respectively.
Nevertheless, it is possible to approximate the overall protostellar
evolution in many cases by pre-computed stellar evolutionary tracks
assuming appropriate constant average accretion rates.
Reference:
ApJ
Status: Manuscript has been accepted
Weblink:
http://arxiv.org/abs/1305.6310
Comments:
Email: Rolf.Kuiper@jpl.nasa.gov
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Grant N. Remmen(1,2), Kris
Davidson(1) and Andrea Mehner (3)
1. School of Physics and
Astronomy, University of Minnesota, Minneapolis, MN 55455
2.
California Institute of Technology, Pasadena, CA 91125
3. ESO,
Alonso de Cordova 3107, Santiago de Chile
The Weigelt knots,
dense slow-moving ejecta near eta Car, are mysterious in structure as
well as in origin. Using spatially dithered spectrograms obtained
with the HST/STIS, we have partially resolved the ionization zones of
one knot. Contrary to simple models, higher ionization levels occur
on the outer side of the knot, i.e., farther from the star. They
cannot represent a bow shock, and no satisfying explanation is yet
available -- though we sketch one qualitative possibility. STIS
spectrograms provide far more reliable spatial measurements of the
Weigelt Knots than HST images do, and this technique can also be
applied to the knots' proper motion problem. Our spatial measurement
accuracy is about 10 mas, corresponding to a projected linear scale
of the order of 30 AU which is appreciably smaller than the size of
each Weigelt knot.
Reference: Astrophysical
Journal
Status: Manuscript has been accepted
Weblink:
Email: kd@astro.umn.edu
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G. Rauw (1), Y. Naze (1), M.
Spano (2), T. Morel (1), & A. ud-Doula (3)
1 -
Institute of Astrophysics and Geophysics, Liege University, Belgium
2 - Geneva Observatory, University of Geneva, Switzerland
3 -
Penn State Worthington Scranton, USA
Oe stars possibly form an
extension to higher temperatures of the Be phenomenon, but it is
still unclear whether these stars have disks. X-ray spectra could
provide hints for interactions of the star with a putative
surrounding disk. We obtained XMM-Newton observations of two Oe
stars, HD45314 and HD60848. Spectra and light curves were extracted
and analysed. Optical spectra were also obtained to support the X-ray
observations. We find that both stars display very different X-ray
properties. Whilst HD60848 has an X-ray spectrum and emission level
typical for its spectral type, HD45314 displays a very hard X-ray
emission, dominated by a thermal plasma with kT ~ 21 keV.
Furthermore, HD45314 displays count rate variations by a factor 2 on
timescales of ~ 1000s and a high log(L_X/L_bol) = -6.10 +/- 0.03. The
X-ray properties of HD45314 indicate that this star is a new member
of the class of gamma Cas analogs, the first one among the original
category of Oe stars.
Reference: A&A Letter, in
press
Status: Manuscript has been accepted
Weblink:
http://arxiv.org/abs/1306.6520
Email:
rauw@astro.ulg.ac.be
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Samuel Jones (1), Raphael Hirschi (1,2), Ken'ichi Nomoto
(2), Tobias Fischer (3,4), Frank X. Timmes (5,6), Falk Herwig (7,6),
Bill Paxton (8), Hiroshi Toki (9), Toshio Suzuki (10,11), Gabriel
Martinez-Pinedo (4,3), Yi Hua Lam (4), Michael G. Bertolli (12)
(1)
Keele University, (2) Kavli IPMU (WPI), (3) GSI, (4) TU Darmstadt,
(5) ASU, (6) JINA, (7) UVic, (8) KITP UCSB, (9) Osaka University,
(10) Nihon University, (11) NAO Japan, (12) LANL
The stellar
mass range 8-12 Mo corresponds to the most massive AGB stars and the
most numerous massive stars. It is host to a variety of supernova
progenitors and is therefore very important for galactic chemical
evolution and stellar population studies. In this paper, we study the
transition from super-AGB star to massive star and find that a
propagating neon-oxygen burning shell is common to both the most
massive electron capture supernova (EC-SN) progenitors and the lowest
mass iron-core collapse supernova (FeCCSN) progenitors. Of the models
that ignite neon burning off-center, the 9.5Mo model would evolve to
an FeCCSN after the neon-burning shell propagates to the center, as
in previous studies. The neon-burning shell in the 8.8Mo model,
however, fails to reach the center as the URCA process and an
extended (0.6 Mo) region of low Ye (0.48) in the outer part of the
core begin to dominate the late evolution; the model evolves to an
EC-SN. This is the first study to follow the most massive EC-SN
progenitors to collapse, representing an evolutionary path to EC-SN
in addition to that from SAGB stars undergoing thermal pulses. We
also present models of an 8.75Mo super-AGB star through its entire
thermal pulse phase until electron captures on 20Ne begin at its
center and of a 12Mo star up to the iron core collapse. We discuss
key uncertainties and how the different pathways to collapse affect
the pre-supernova structure. Finally, we compare our results to the
observed neutron star mass distribution.
Reference:
Accepted for publication in ApJ
Status: Manuscript has been
accepted
Weblink: http://arxiv.org/abs/1306.2030
Comments:
Email: s.w.jones@keele.ac.uk
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Hideyuki Saio$^1$, Cyril
Georgy $^2$, and Georges Meynet$^3$
1-Astronomical
Institute, Tohoku University; 2-Centre de Recherche Astrophysique de
Lyon, and Lennard-Jones Laboratories, EPSAM, Keele University;
3-Geneva Observatory, University of Geneva
If a massive star
has lost significant mass during its red-supergiant stage, it would
return to blue region in the HR diagram and spend a part of the
core-He burning stage as a blue supergiant having a luminosity to
mass ratio (L/M) considerably larger than about 10^4 (in solar
units); the duration depends on the degree of internal mixing and on
the metallicity. Then, various stellar pulsations are excited by
enhanced kappa-mechanism and strange mode instability. Assuming these
pulsations to be responsible for (at least some of) the
quasi-periodic light and radial-velocity variations in alpha Cygni
variables including luminous blue variables (LBVs; or S Dor
variables), we can predict masses and surface compositions for these
variables, and compare them with observed ones to constrain the
evolutionary models. We discuss radial pulsations excited in
evolutionary models of an initial mass of 40 M_odot with solar
metallicity of Z=0.014, and compare them to micro-variations in the
two Galactic LBVs, HR Car and HD 160529. We have found that these
stars should has lost more than half of the initial mass and their
surface CNO abundances should be significantly modified from the
original ones showing partial H-burning products.
Reference:
Fujiwara Seminar "Progress in Physics
of the Sun and
Stars: A New Era in Helio- and Asteroseismology" 26 - 29 Nov.
2012, Hakone, Japan
Status: Conference proceedings
Weblink:
http://arxiv.org/abs/1305.4728
Comments:
Email: saio@astr.tohoku.ac.jp
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J. Maíz Apellániz (1), A. Sota (1),
N. I. Morrell (2), R. H. Barbá (3), N. R. Walborn (4), E. J. Alfaro
(1), R. C. Gamen (5), J. I. Arias (3), and A. T. Gallego Calvente
(1)
(1) Instituto de Astrofísica de Andalucía-CSIC,
Granada, Spain; (2) Las Campanas Observatory, La Serena, Chile; (3)
Departamento de Física, Universidad de La Serena, La Serena, Chile;
(4) Space Telescope Science Institute, Baltimore, MD, USA; (5)
Instituto de Astrofísica de La Plata (CONICET, UNLP), La Plata,
Argentina
The Galactic O-Star Spectroscopic Survey (GOSSS) is
obtaining high quality R~2500 blue-violet spectroscopy of all
Galactic stars ever classified as of O type with B < 12 and a
significant fraction of those with B = 12-14. As of June 2013, we
have obtained, processed, and classified 2653 spectra of 1593 stars,
including all of the sample with B < 8 and most of the sample with
B = 8-10, making GOSSS already the largest collection of high quality
O-star optical spectra ever assembled by a factor of 3. We discuss
the fraction of false positives (stars classified as O in previous
works that do not belong to that class) and the implications of the
observed magnitude distribution for the spatial distribution of
massive stars and dust within a few kpc of the Sun. We also present
new spectrograms for some of the interesting objects in the sample
and show applications of GOSSS data to the study of the intervening
ISM. Finally, we present the new version of the Galactic O-Star
Catalog (GOSC), which incorporates the data in GOSSS-DR1, and we
discuss our plans for MGB, an interactive spectral classification
tool for OB stars.
Reference: 13 pages, 9 figures. To
appear in "Massive Stars: From alpha to Omega", a meeting
held in Rhodes, Greece, on 10-14 June 2013.
Status: Conference
proceedings
Weblink:
Comments:
Email:
jmaiz@iaa.es
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Ted Gull(1), Michael
Corcoran(1,2), Augusto Damineli(3), Kenji Hamaguchi(1,4), Thomas
Madura(1,5), Mairan Teodoro(1,6)
(1) NASA/GSFC, (2) CREST,
(3) Univ Sao Paulo, (4) UMBC, (5) NPP, (6) Brazil Science w/o
Borders
Eta Carinae continues to challenge both observers and
modelers as it changes in apparent brightness and spectroscopic
properties, both with a 5.5-year periodicity and in the long term.
Eta Carinae will go through its next periastron passage in
late July 2014. As noted by Mairan Teodoro (mairan.teodoro@nasa.gov)
in the November/December 2012 Massive Star Newsletter, a call is out
for coordination of an international campaign for ground-based
monitoring of this event (see www.etacar2014.wikidot.com .
We
bring to your attention several additional programs: an HST/STIS
multi-cycle program to map the interacting winds of Eta Carinae (see
Gull et al 2009 MNRAS 396, 1308, Gull et al 2011 ApJ 743, L3 and HST
programs 12750, 13014), is scheduled to continue at critical
samplings across periastron through January 2015; ongoing X-Ray flux
monitoring is being proposed by Mike Corcoran to use Swift to extend
the studies accomplished with RXTE (see Corcoran et al, 2010 ApJ 725,
1528); ongoing CHANDRA/XMM/SUZAKU X-ray spectral studies (see
Hamaguchi et al., 2012, ASPC 465, 325); 3D hydrodynamic models are
being developed to increasingly characterize the interacting winds of
the massive binary system and derive properties of the two massive
companions (see Parkin et, 2009 MNRAS 400, 1657; Madura et al, 2012
MNRAS 420, 2064; Russell 2013 PhD thesis, UDel).
The American
Astronomical Society Meeting 223 is scheduled for the first week in
January 2014 near Washington, DC, USA. We are proposing a one-day
splinter session within the meeting with the purpose to bring
together researchers interested in providing and coordinating
observations and/or models pertaining to the behavior of this
intriguing binary system. Likely the session would be separated into
two parts: what we currently know about the binary, its winds and
ejecta and what we need to learn from the periastron event by either
observation or theory.
Given the widespread interest in this
massive star system, we would like to obtain an estimate of those who
plan to attend and we solicit potential contributions to the splinter
session independent of the main meeting. A previous session held at
Mt. Rainer in 2001 for the Hubble Treasury Eta Carinae Program had an
attendance of approximately 40 interested researchers. A special
session at the 2009 IAU General Assembly had well over 100 attendees.
Contributions to this splinter session will be separate from the main
meeting. Posters and talks on Eta Carinae in the scheduled AAS
meeting sessions are strongly encouraged, and will be separate from
this splinter session intended to provide a focussed review on what
is known about Eta Carinae and what we wish to learn through studies
of the upcoming periastron event.
Those interested in
participating in and/or contributing to the session should contact
Ted Gull (Ted.Gull@nasa.gov) by 1 August 2013.
Reference:
AAS Meeting 223 proposal
Status: Other
Weblink:
Comments:
Email:
Ted.Gull@nasa.gov
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Prof. Dr. Ulrich Heber
Dr.
Remeis-Sternwarte & ECAP
Astronomisches Institut
Universität
Erlangen-Nürnberg
Sternwartstr. 7
D 96049 Bamberg
Germany
Applications are invited for a research position
in the stellar
astrophysics group of the Dr. Remeis-Sternwarte
Bamberg, which is the
astronomical institute of the University
Erlangen-Nuremberg. The
appointment starts October 1st, 2013 and
can be made at the post-doctoral
level for 18 month or
alternatively for three years at the PhD level. The
successful
applicant is expected to carry out quantitative spectral
analyses
of high-resolution ultraviolet spectra of hot evolved stars
obtained
with the Hubble Space Telescope. XMM-Newton observations shall be
exploited to search for X-ray emission from wind accretion in an
enigmatic
sdB binary. Applicants should have sound knowledge of
stellar astrophysics
at the appropriate level. Detailed expertise
in quantitative stellar
spectroscopy would be of advantage.
The
remuneration is according to the German public salary scale TV-L
level
13 (full time) for the post-doctoral level and at the TV-L
level 13/2
(20.05 hours per week) at the PhD level. Benefits are
according to the public service rules and include unemployment,
healthcare
and
retirement benefits.
Please send a
curriculum vitae, brief statement of research interests and
give
the names of three referees, who might be asked for letters of
reference.
Please send your application before June, 1,
2013,
by email to
ulrich.heber@sternwarte.uni-erlangen.de
or by mail to
Prof. Dr. Ulrich Heber
Astronomisches
Institut
Universität Erlangen-Nürnberg
Sternwartstr. 7
D96049 Bamberg
Germany
Please state clearly whether
you apply for a post-doctoral position or a
PhD
project.
Attention/Comments:
Weblink:
http://www.sternwarte.uni-erlangen.de/ausschreib_dlr.pdf
Email:
heber@sternwarte.uni-erlangen.de
Deadline: June 1,
2013
Back to contents
Sally Oey
University
of Michigan
Astronomy Department
830 Dennison Building
Ann
Arbor, MI 48109-1042
USA
Applications are invited for a
postdoctoral position at the University of Michigan to work with
Prof. Sally Oey on projects related to radiative feedback from
massive stars, in particular, HII regions and the escape fraction of
ionizing radiation. There also may be opportunity in the area of OB
stars and massive star populations. The successful candidate will
have access to the University of Michigan telescope facilities,
including the twin 6.5-m Magellan Telescopes at Las Campanas, and the
MDM 2.4-m and 1.3-m telescopes at Kitt Peak. Our department has a
vibrant environment with several journal clubs and discussion groups.
This position is available for two years, with possible extension for
a third. The start date is flexible, to begin as soon as possible.
Applicants should have a Ph.D., and the ideal candidate will
have experience with HII region imaging, spectroscopy, and
photoionization
modeling.
To apply, please submit
curriculum vitae, statement of research interests, and contact
details for three references. Applications must be submitted via
umjobs.org. Reference job posting ID 81575. Please include your
available start date, and ALSO send a direct email to msoey@umich.edu
to confirm that your application has been submitted. Applications
received by 15 June 2013 will receive first consideration.
Inquiries may be directed to Sally Oey (msoey@umich.edu).
The University of Michigan is an Equal
Opportunity/Affirmative Action Employer. Women and minorities are
encouraged to apply.
Attention/Comments:
Weblink:
http://umjobs.org
Email:
msoey@umich.edu
Deadline: June 30
Back
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conny.aerts@ster.kuleuven.be
Instituut
voor sterrenkunde
KU Leuven
Celestijnenlaan 200D
3001
Heverlee
Belgium
fys.kuleuven.be/ster
In the Science,
Engineering & Technology Group, Faculty of Science, Department of
Physics and Astronomy at KU Leuven there is a full-time academic
vacancy among senior academic staff in the area of Astronomy and
Astrophysics. We are looking for internationally oriented candidates
with an excellent research record and with educational competence
within the field of numerical modelling of stellar interiors.
You
are expected to collaborate with scientists of the Institute of
Astronomy (IoA) in the Department of Physics and Astronomy on the one
hand, and of the Centre for mathematical Plasma-Astrophysics (CmPA)
in the Department of Mathematics on the other hand. Both research
groups are embedded within the Faculty of Science. In the past, this
faculty has systematically been given a high ranking for research and
education quality by independent accreditation committees. The
faculty has an extensive national and international network.
The
IoA and CmPA are research centres with expertise in the topics of
stellar structure and evolution, asteroseismology, interstellar and
circumstellar matter, the chemistry of exoplanetary atmospheres,
binary stars, solar physics, high-performance computing (HPC) in a
general plasma-physical context, and MHD and kinetic descriptions of
space weather. They rely on the involvement in international space
missions, ground-based telescopes, and HPC-driven fundamental
research collaborations.
http:// fys.kuleuven.be/ster
http://wis.kuleuven.be/CmPA
*Duties*
*Research
You are expected to perform high-level research in the field
of numerical modelling of stellar interiors. The modelling should
include angular momentum transport inside stars, with a focus on the
role of internal differential rotation patterns, atomic diffusion
processes, magnetic field generation, magnetoconvection, etc.,
through state-of-the-art local numerical magnetohydrodynamical
simulations. The simulations need to provide high-resolution insights
in local magnetohydrodynamics, as well as be applicable to global
spherical scale geometry. Global models need to connect to current
knowledge of stellar structure, variability, evolution and stellar
coronal activity, and need to find feedback in spectroscopic,
interferometric and asteroseismic diagnostics derived from modern
data.
*Teaching
You ensure high-quality education
within the area of astronomy and astrophysics, physics, and
mathematics, with a clear commitment for the quality of the programme
as a whole. You also contribute to the pedagogic project of the
faculty/university through the supervision of master theses and as
supervisor of PhD students.
You develop your teachings in
accordance with KU Leuven's vision on activating and researched-based
education and make use of the possibilities for the educationalist
professionalisation offered by the faculty and the university.
*Service
Besides the research and the teaching
assignment, you are expected to be willing to provide services to the
community, in particular to amateur astronomer organisations, to the
government and to Belgian industry in the framework of instrument
development in the topics of the research task, in a Belgian as well
as an international context.
*Requirements*
You have
a PhD or doctoral degree in Astrophysics, Mathematics, Physics or
equivalent.
You are an expert in theoretical-computational
studies of stellar interiors confirmed by an excellent peer-reviewed
publication record. Awareness and understanding of the observational
aspects of stellar evolution are assets.
You have very good
teaching and training skills, in order to contribute to the quality
of the department's educational program.
Near-native
proficiency of English is required. KU Leuven provides courses in
academic English.
The administrative and educational language
at KU Leuven is Dutch. If, at your appointment, you do not speak
Dutch at all or do not speak it well, KU Leuven will provide a
training offer that must equip you to be able to teach in Dutch
within three years. If your teaching assignment is completely in a
language other than Dutch, then it is expected that you have mastered
the Dutch language to a level that will allow you to participate in
the administrative meetings.
*Offer*
We are offering
full-time employment in an intellectually challenging environment. KU
Leuven is a research-intensive, internationally oriented university
that carries out both fundamental and applied scientific research. It
is highly inter- and multidisciplinary focused and strives for
international excellence. In this regard, it actively works together
with research partners in Belgium and abroad. It provides its
students with an academic education that is based on high-quality
scientific research.
You will work in Leuven, a historic,
dynamic and lively city located in the heart of Belgium, within 20
minutes from Brussels, the capital of the European Union, and less
than two hours from Paris, London and Amsterdam.
Depending on
your record and qualifications, you will be appointed to or tenured
in one of the grades of the senior academic staff: assistant
professor, associate professor, professor or full professor. In
principle, junior researchers are appointed as tenure-track assistant
professor for a period of 5 years; after this period and a positive
evaluation, they are permanently appointed (or tenured) as an
associate professor.
Attention/Comments: Apply online
following the weblink
Weblink:
https://icts.kuleuven.be/apps/jobsite/vacatures/52451655?lang=en
Email:
conny.aerts@ster.kuleuven.be
Deadline: September
30, 2014
Back to contents
2013 July 29 - August
2
Venue: Hyatt Regency Hotel, Monterey,
California
"Giants of Eclipse" will provide a forum
to discuss the physics of cool giant stars, examine new data for
those objects, and compare the latest theories. Studies of giants in
eclipsing binaries have afforded us a means of deriving precise
cool-star physics, and the role of these systems as astrophysical
calibrators is central to the meeting. The minute details of the
eclipses of ζ Aurigae systems and other binaries will be examined
along with new results from the mysterious two-year eclipse of ε
Aurigae. Some of the long-standing and challenging aspects of these
systems are now being tackled with new-generation techniques, and
novel technologies such as Kepler, involving young
scientists.
Weblink:
http://aas.org/meetings/aastcs-3-giants-eclipse-meeting-monterey-california
Email:
elizabeth.griffin@nrc-cnrc.gc.ca
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2013, August 25-30
Venue: Biarritz,
France
The program of IAUS 302 is now available online!
http://iaus302.sciencesconf.org/program
The full list of
abstracts (including posters) can be found here:
http://iaus302.sciencesconf.org/browse/session
The
deadline for registration is on July 21! To join us in Biarritz at
the end of August, we invite you to proceed to the registration page:
http://iaus302.sciencesconf.org/registration/index
The
SOC and LOC of IAUS 302
Weblink:
http://iaus302.sciencesconf.org
Email:
iaus302@sciencesconf.org
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contents