ISSN 1783-3426
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Fizeau exchange visitors program – call for applications.
First detections of FS CMa stars in
clusters. Evolutionary state as constrained by coeval massive
stars
Spectroscopic variability of
two Oe stars
What causes the large
extensions of red-supergiant atmospheres? Comparisons of
interferometric observations with 1-D hydrostatic, 3-D convection,
and 1-D pulsating model atmospheres
Code
dependencies of pre-supernova evolution and nucleosynthesis in
massive stars: evolution to the end of core helium burning
The
Final Fate of Stars that Ignite Neon and Oxygen Off-center: Electron
Capture or Iron Core-collapse Supernova?
Early-time
spectra of supernovae and their precursor winds: the luminous blue
variable/yellow hypergiant progenitor of SN 2013cu
Three-dimensional
modeling of ionized gas. II. Spectral energy distributions of massive
and very massive stars in stationary and time-dependent modeling of
the ionization of metals in HII regions
Polarimetric
modeling of corotating interaction regions (CIRs) threading
massive-star winds
Orbital and
Physical Properties of the sigma Ori Aa, Ab, B Triple
System
Multiwavelength Observations
of NaSt1 (WR 122): Equatorial Mass Loss and X-rays from an
Interacting Wolf-Rayet Binary
No
breakdown of the radiatively-driven wind theory in low-metallicity
environments
From the atmosphere to the circumstellar environment in cool evolved stars
Closed (original deadline passed):
PhD Studentships (STFC/Keele funding) in Astronomy/Astrophysics
Open:
PhD Position on Quantitative Stellar
Spectroscopy
Job opening for two
post-doctoral and two PhD positions in the field of evolved stars and
laboratory experiments
Stellar End
Products: The Low Mass - High Mass Connection
F.O.E.
Fifty-One Erg - International Conference on the Physics and
Observations of Supernovae and Supernova Remnants
St
Andrews Monte Carlo Summer School
Science
with large spectroscopic surveys of Galactic OB stars: getting ready
for Gaia
Stellar Behemoths: Red
Supergiants Across the Local Universe
Massive
Stars and the Gaia-ESO Survey
The Fizeau exchange visitors
program in optical interferometry funds (travel and accommodation)
visits of researchers to an institute of his/her choice (within the
European Community) to perform collaborative work and training on one
of the active topics of the European Interferometry Initiative. The
visits will typically last for one month, and strengthen the network
of astronomers engaged in technical, scientific
and training work
on optical/infrared interferometry. The program is open for all
levels of astronomers (Ph.D. students to tenured staff), non-EU based
missions will only be funded if considered essential by the Fizeau
Committee. Applicants are strongly encouraged to seek also partial
support from their home or host institutions.
The deadline
for applications is March 15. Fellowships can be awarded for missions
starting in May.
NOTE: a special Fizeau call will be issued
in late April for financial support requests for the VLTI school 2015
in Cologne:
http://www.astro.uni-koeln.de/vltischool2015
Further informations and application forms can be found at
www.european-interferometry.eu
The program is funded by
OPTICON/FP7.
Please distribute this message also to
potentially interested colleagues outside of your community!
Looking forward to your applications,
Josef Hron &
Laszlo Mosoni
(for the European Interferometry
Initiative)
Weblink: www.european-interferometry.eu
Email:
fizeau@european-interferometry.eu
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D. de la Fuente(1), F. Najarro(1), C. Trombley(2), B.
Davies(3), and D. F. Figer(2)
1 - Centro de Astrobiologia,
CSIC/INTA (Madrid, Spain); 2 - Center for Detectors, Rochester
Institute of Technology (NY, USA); 3 - Astrophysics Research
Institute, Liverpool John Moores University (UK)
FS CMa stars
are low-luminosity objects showing the B[e] phenomenon whose
evolutionary state remains a puzzle. These stars are surrounded by
compact disks of warm dust of unknown origin. Hitherto, membership of
FS CMa stars to coeval populations has never been confirmed. The
discovery of low-luminosity line emitters in the young massive
clusters Mercer 20 and Mercer 70 prompts us to investigate the nature
of such objects. We intend to confirm membership to coeval
populations in order to characterize these emission-line stars
through the cluster properties. Based on ISAAC/VLT medium-resolution
spectroscopy and NICMOS/HST photometry of massive cluster members,
new characterizations of Mercer 20 and Mercer 70 are performed.
Coevality of each cluster and membership of the newly-discovered B[e]
objects are investigated using our observations as well as literature
data of the surroundings. Infrared excess and narrow-band photometric
properties of the B[e] stars are also studied. We confirm and
classify 22 new cluster members, including Wolf-Rayet stars and blue
hypergiants. Spectral types (O9-B1.5 V) and radial velocities of B[e]
objects are compatible with the remaining cluster members, while
emission features of Mg II, Fe II], and [Fe II] are identified in
their spectra. The ages of these stars are 4.5 and 6 Myr, and they
show mild infrared excesses. We confirm the presence of FS CMa stars
in the coeval populations of Mercer 20 and Mercer 70. We discuss the
nature and evolutionary state of FS CMa stars, discarding a post-AGB
nature and introducing a new hypothesis about mergers. A new search
method for FS CMa candidates in young massive clusters based on
narrow-band Paschen-alpha photometry is proposed and tested in
photometric data of other clusters, yielding three new
candidates.
Reference: Accepted for publication in
A&A
Status: Manuscript has been accepted
Weblink:
http://arxiv.org/abs/1412.7988
Email:
delafuente@cab.inta-csic.es
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G. Rauw$^{1,2}$, T. Morel$^{1,2}$, Y. Naze$^1$, T.
Eversberg$^{2,3}$, F. Alves$^2$, W. Arnold$^2$, T. Bergmann$^2$, N.G.
Correia Viegas$^2$, R. Fahed$^{2,4}$, A. Fernando$^2$, J.N.
Gonzalez-Perez$^5$, L.F. Gouveia Carreira$^2$, A. Hempelmann$^5$, T.
Hunger$^2$, J.H. Knapen$^{2,6,7}$, R. Leadbeater$^2$, F. Marques
Dias$^2$, M. Mittag$^5$, A.F.J. Moffat$^{2,4}$, N. Reinecke$^2$, J.
Ribeiro$^2$, N. Romeo$^2$, J. Sanchez Gallego$^{2,6,8}$, E.M. Dos
Santos$^2$, L. Schanne$^2$, J.H.M.M. Schmitt$^5$, K.-P.
Schroeder$^9$, O. Stahl$^{2,10}$, Ba. Stober$^2$, Be. Stober$^2$, K.
Vollmann$^{2,3}$
1 - Liege University, Belgium; 2 - Mons
Pro-Am collaboration; 3 - Schnoerringen Telescope Science Institute,
Germany; 4 - University of Montreal, Canada; 5 - Hamburger
Sternwarte, Germany; 6 - Instituto de Astrofisica de Canarias, Spain;
7 - Departamento de Astrofisica de Canarias, Spain; 8 - University of
Kentucky, USA; 9 - Universidad de Guanajuato, Mexico; 10 - University
of Heidelberg, Germany
The two Oe stars HD 45314 and HD 60848
have recently been found to exhibit very different X-ray properties:
whilst HD 60848 has an X-ray spectrum and the emission level typical
of most OB stars, HD 45314 features a much harder and brighter X-ray
emission, making it a so-called gamma Cas analogue. Monitoring the
optical spectra could provide hints towards the origin of these very
different behaviours. We analyse a large set of spectroscopic
observations of HD 45314 and HD 60848, extending over 20 years. We
further attempt to fit the H-alpha line profiles of both stars with a
simple model of emission line formation in a Keplerian disk. Strong
variations in the strengths of the H-alpha, H-beta, and He I 5876
emission lines are observed for both stars. In the case of HD 60848,
we find a time lag between the variations in the equivalent widths of
these lines, which is currently not understood. The emission lines
are double peaked with nearly identical strengths of the violet and
red peaks. The H-alpha profile of this star can be successfully
reproduced by our model of a disk seen under an inclination of 30
degrees. In the case of HD 45314, the emission lines are highly
asymmetric and display strong line profile variations. We find a
major change in behaviour between the 2002 outburst and the one
observed in 2013. This concerns both the relationship between the
equivalent widths of the various lines and their morphologies at
maximum strength (double-peaked in 2002 versus single-peaked in
2013). Our simple disk model fails to reproduce the observed H-alpha
line profiles of HD 45314. Our results further support the
interpretation that Oe stars do have decretion disks similar to those
of Be stars. Whilst the emission lines of HD 60848 are explained well
by a disk with a Keplerian velocity field, the disk of HD 45314 seems
to have a significantly more complex velocity field that could be
another signature of the phenomenon that produces its peculiar X-ray
emission.
Reference: A&A (in press)
Status:
Manuscript has been accepted
Weblink:
http://arxiv.org/abs/1501.01377
Comments:
Email: rauw@astro.ulg.ac.be
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B. Arroyo-Torres (1); M. Wittkowski (2); A. Chiavassa (3);
M. Scholz (4,5); B. Freytag (6); J. Marcaide (1,7); P. H. Hauschildt
(8); P. R. Wood (9); F. J. Abellan (1)
(1) University of
Valencia, Spain
(2) ESO Garching, Germany
(3) University of
Nice Sophia-Antipolis, France
(4) University of Heidelberg,
Germany
(5) University of Sydney, Australia
(6) University of
Uppsala, Sweden
(7) Donostia International Physics Center, Spain
(8) University of Hamburg, Germany
(9) Australian National
University, Australia
We present the atmospheric structure and
the fundamental parameters of three red supergiants, increasing the
sample of RSGs observed by near-infrared spectro-interferometry.
Additionally, we test possible mechanisms that may explain the large
observed atmospheric extensions of RSGs. We carried out
spectro-interferometric observations of 3 RSGs in the near-infrared
K-band with the VLTI/AMBER instrument at medium spectral resolution.
To comprehend the extended atmospheres, we compared our observational
results to predictions by available hydrostatic PHOENIX, available
3-D convection, and new 1-D self-excited pulsation models of RSGs.
Our near-infrared flux spectra are well reproduced by the PHOENIX
model atmospheres. The continuum visibility values are consistent
with a limb-darkened disk as predicted by the PHOENIX models,
allowing us to determine the angular diameter and the fundamental
parameters of our sources. Nonetheless, in the case of V602 Car and
HD 95686, the PHOENIX model visibilities do not predict the large
observed extensions of molecular layers, most remarkably in the CO
bands. Likewise, the 3-D convection models and the 1-D pulsation
models with typical parameters of RSGs lead to compact atmospheric
structures as well, which are similar to the structure of the
hydrostatic PHOENIX models. They can also not explain the observed
decreases in the visibilities and thus the large atmospheric
molecular extensions. The full sample of our RSGs indicates
increasing observed atmospheric extensions with increasing luminosity
and decreasing surface gravity, and no correlation with effective
temperature or variability amplitude, which supports a scenario of
radiative acceleration on Doppler-shifted molecular
lines.
Reference: A&A, in press
Status:
Manuscript has been accepted
Weblink:
http://adsabs.harvard.edu/abs/2015arXiv150101560A
Comments:
Email: mwittkow@eso.org
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S. Jones(1,2,*), R. Hirschi(2,3,*), M. Pignatari(4,*), A.
Heger(5,6,7,*), C. Georgy(2), N. Nishimura(2,*), C. Fryer(8,*) &
F. Herwig(1,7,*)
(1) University of Victoria (2) Keele
University (3) Kavli IPMU (WPI) (4) University of Basel (5) Monash
University (6) University of Minnesota (7) JINA (8) LANL
* NuGrid
Collaboration, www.nugridstars.org
Massive stars are key
sources of radiative, kinetic and chemical feedback in the Universe.
Grids of massive star models computed by different groups each using
their own codes, input physics choices and numerical approximations,
however, lead to inconsistent results for the same stars. We use
three of these 1D codes --- GENEC, KEPLER and MESA --- to compute
non-rotating stellar models of 15, 20 and 25 M&sun; and compare
their nucleosynthesis. We follow the evolution from the main sequence
until the end of core helium burning. The GENEC and KEPLER models
hold physics assumptions used in large grids of published models. The
MESA code was set up to use convective core overshooting such that
the CO core masses are consistent with those obtained by GENEC. For
all models, full nucleosynthesis is computed using the NuGrid
post-processing tool MPPNP. We find that the surface abundances
predicted by the models are in reasonable agreement. In the helium
core, the standard deviation of the elemental overproduction factors
for Fe to Mo is less than 30 per cent - smaller than the impact of
the present nuclear physics uncertainties. For our three initial
masses, the three stellar evolution codes yield consistent results.
Differences in key properties of the models, e.g. helium and CO core
masses and the time spent as a red supergiant, are traced back to the
treatment of convection and, to a lesser extent, mass loss. The
mixing processes in stars remain the key uncertainty in stellar
modelling. Better constrained prescriptions are thus necessary to
improve the predictive power of stellar evolution models.
Reference:
MNRAS 447, 3115-3129 (2015)
Status: Manuscript has been
accepted
Weblink:
http://adsabs.harvard.edu/abs/2015MNRAS.447.3115J
Comments:
Email: swjones@uvic.ca
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Samuel Jones(1), Raphael Hirschi(2,3), Ken'ichi
Nomoto(3)
(1) University of Victoria (2) Keele University
(3) Kavli IPMU (WPI)
In the ONeMg cores of 8.8-9.5 M ☉
stars, neon and oxygen burning is ignited off-center. Whether or not
the neon-oxygen flame propagates to the center is critical for
determining whether these stars undergo Fe core collapse or
electron-capture-induced ONeMg core collapse. We present more details
of stars that ignite neon and oxygen burning off-center. The neon
flame is established in a manner similar to the carbon flame of
super-AGB stars, albeit with a narrower flame width. The criteria for
establishing a flame can be met if the strict Schwarzschild criterion
for convective instability is adopted. Mixing across the interface of
the convective shell disrupts the conditions for the propagation of
the burning front, and instead the shell burns as a series of
inward-moving flashes. While this may not directly affect whether or
not the burning will reach the center (as in super-AGB stars), the
core is allowed to contract between each shell flash. Reduction of
the electron fraction in the shell reduces the Chandrasekhar mass and
the center reaches the threshold density for the URCA process to
activate and steer the remaining evolution of the core. This
highlights the importance of a more accurate treatment of mixing in
the stellar interior for yet another important question in stellar
astrophysics---determining the properties of stellar evolution and
supernova progenitors at the boundary between electron capture
supernova and iron core-collapse supernova.
Reference: ApJ
797 83
Status: Manuscript has been accepted
Weblink:
http://adsabs.harvard.edu/abs/2014ApJ...797...83J
Comments:
Email: swjones@uvic.ca
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Jose Groh
Geneva Observatory, Switzerland
We
present the first quantitative spectroscopic modeling of an
early-time supernova (SN) that interacts with its progenitor wind.
Using the radiative transfer code CMFGEN, we investigate the recently
reported 15.5 h post-explosion spectrum of the type IIb SN 2013cu. We
are able to directly measure the chemical abundances of a SN
progenitor and find a relatively H-rich wind, with H and He
abundances (by mass) of X = 0.46 +- 0.2 and Y = 0.52 +- 0.2,
respectively. The wind is enhanced in N and depleted in C relative to
solar values (mass fractions of 8.2e-3 and 1.0e-5, respectively). We
obtain that a slow, dense wind or circumstellar medium surrounds the
precursor at the pre-SN stage, with a wind terminal velocity vwind <
100 km/s and mass-loss rate of Mdot ≃ 3e-3 (vwind/ 100 km/s)
Msun/yr. These values are lower than previous analytical estimates,
although Mdot/vwind is consistent with previous work. We also compute
a CMFGEN model to constrain the progenitor spectral type; the high
Mdot and low vwind imply that the star had an effective temperature
of ~ 8000 K immediately before the SN explosion. Our models suggest
that the progenitor was either an unstable luminous blue variable or
a yellow hypergiant undergoing an eruptive phase, and rule out a
Wolf-Rayet star. We classify the post-explosion spectra at 15.5 h as
XWN5(h) and advocate for the use of the prefix "X"
(eXplosion) to avoid confusion between post-explosion, non-stellar
spectra, and those of massive stars. We show that the XWN spectrum
results from the ionization of the progenitor wind after the SN, and
that the progenitor spectral type is significantly different from the
early post-explosion spectral type owing to the huge differences in
the ionization structure before and after the SN event. We find the
following temporal evolution: LBV/YHG -> XWN5(h) -> SN IIb.
Future early-time spectroscopy in the UV will further constrain the
properties of SN precursors, such as their metallicities.
Reference:
Groh, J. 2014, A&A 572, L11
Status: Manuscript has been
accepted
Weblink:
http://adsabs.harvard.edu/abs/2014A%26A...572L..11G
Comments:
Email: jose.groh@unige.ch
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J. A. Weber, A. W. A. Pauldrach, T. L. Hoffmann
Institut
für Astronomie und Astrophysik der Universitaet Muenchen,
Scheinerstrasse 1, 81679 Muenchen, Germany
HII regions play a
crucial role in the measurement of the chemical
composition of
the interstellar medium and provide fundamental data about
element
abundances that constrain models of galactic chemical evolution.
Discrepancies that still exist between observed emission line
strengths and
those predicted by nebular models can be partly
attributed to the spectral
energy distributions (SEDs) of the
sources of ionizing radiation used in the
models as well as
simplifying assumptions made in nebular modeling. The
influence
of stellar metallicity on nebular line strength ratios, via its
effect on the SEDs, is of similar importance as variations in the
nebular
metallicity. We have computed a grid of model atmosphere
SEDs for massive and
very massive O-type stars covering a range
of metallicities from significantly
subsolar (0.1 Zsun) to
supersolar (2 Zsun). The SEDs have been computed using a
state-of-the-art model atmosphere code that takes into account
the attenuation
of the ionizing flux by the spectral lines of all
important elements and the
hydrodynamics of the radiatively
driven winds and their influence on the SEDs.
For the assessment
of the SEDs in nebular simulations we have developed a
(heretofore
not available) 3d radiative transfer code that includes a
time-dependent treatment of the metal ionization. Using the SEDs
in both 1d and
3d nebular models we explore the relative
influence of stellar metallicity, gas
metallicity, and
inhomogeneity of the gas on the nebular ionization structure
and
emission line strengths. We find that stellar and gas metallicity are
of
similar importance for establishing the line strength ratios
commonly used in
nebular diagnostics, whereas inhomogeneity of
the gas has only a subordinate
influence on the global line
emission.
Reference: Publication in A&A. Pre-print
available on astro-ph.
Status: Manuscript has been
accepted
Weblink:
http://arxiv.org/abs/1501.05264
Comments:
Two-column style: 35 pages, 20 figures, and 8 tables.
Email:
uh10107@usm.uni-muenchen.de
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R Ignace^1, N St-Louis^2, F Proulx-Giradeua^2
1
East Tennessee State University
2 University of
Montreal
Context. Massive star winds are complex
radiation-hydrodynamic (sometimes magnetohydrodynamic) outflows that
are propelled by their enormously strong luminosities. The winds are
often found to be structured and variable, but can also display
periodic or quasi-periodic behavior in a variety of wind diagnostics.
Aims. The regular variations observed in putatively single stars,
especially in UV wind lines, have often been attributed to corotating
interaction regions (CIRs) like those seen in the solar wind. We
present light curves for variable polarization from winds with CIR
structures.
Methods. We develop a model for a time-independent
CIR based on a kinematical description. Assuming optically thin
electron scattering, we explore the range of polarimetric light
curves that result as the curvature, latitude, and number of CIRs are
varied. Results. We find that a diverse array of variable
polarizations result from an exploration of cases. The net
polarization from an unresolved source is weighted more toward the
inner radii of the wind. Given that most massive stars have
relatively fast winds compared to their rotation speeds, CIRs tend to
be conical at inner radii, transitioning to a spiral shape at a few
to several stellar radii in the wind.
Conclusions. Winds with a
single CIR structure lead to easily identifiable polarization
signatures. By contrast allowing for multiple CIRs, all emerging from
a range of azimuth and latitude positions at the star, can yield
complex polarimetric behavior. Although our model is based on some
simplifying assumptions, it produces qualitative behavior that we
expect to be robust, and this has allowed us to explore a wide range
of CIR configurations that will prove useful for interpreting
polarimetric data.
Reference: Astronomy and
Astrophysics
Status: Manuscript has been accepted
Weblink:
http://arxiv.org/abs/1501.07563
Comments:
Email: ignace@etsu.edu
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Simón-Díaz, S.; Caballero, J. A.; Lorenzo, J.; Maíz
Apellániz, J.; Schneider, F. R. N.; Negueruela, I.; Barbá, R. H.;
Dorda, R.; Marco, A.; Montes, D.; Pellerin, A.; Sanchez-Bermudez, J.;
Sódor, Á.; Sota, A.
IAC/ULL, CAB/CSIC, Univ. Alicante
+
We provide a complete characterization of the astrophysical
properties of the sigma Ori Aa, Ab, B hierarchical triple system and
an improved set of orbital parameters for the highly eccentric sigma
Ori Aa, Ab spectroscopic binary. We compiled a spectroscopic data set
comprising 90 high-resolution spectra covering a total time span of
1963 days. We applied the Lehman-Filhés method for a detailed
orbital analysis of the radial velocity curves and performed a
combined quantitative spectroscopic analysis of the sigma Ori Aa, Ab,
B system by means of the stellar atmosphere code FASTWIND. We used
our own plus other available information on photometry and distance
to the system for measuring the radii, luminosities, and
spectroscopic masses of the three components. We also inferred
evolutionary masses and stellar ages using the Bayesian code BONNSAI.
The orbital analysis of the new radial velocity curves led to a very
accurate orbital solution of the sigma Ori Aa, Ab pair. We provided
indirect arguments indicating that sigma Ori B is a fast-rotating
early B dwarf. The FASTWIND+BONNSAI analysis showed that the Aa, Ab
pair contains the hottest and most massive components of the triple
system while sigma Ori B is a bit cooler and less massive. The
derived stellar ages of the inner pair are intriguingly younger than
the one widely accepted for the sigma Orionis cluster, at 3 ± 1 Ma.
The outcome of this study will be of key importance for a precise
determination of the distance to the sigma Orionis cluster, the
interpretation of the strong X-ray emission detected for sigma Ori
Aa, Ab, B, and the investigation of the formation and evolution of
multiple massive stellar systems and substellar objects.
Reference:
2015, ApJ 799, 169S
Status: Manuscript has been
accepted
Weblink:
http://adsabs.harvard.edu/abs/2015ApJ...799..169S
Comments:
IAC press release:
http://www.iac.es/divulgacion.php?op1=16&id=911〈=en
Animation
(youtube): https://www.youtube.com/watch?v=t42YdyfkizI
Email:
ssimon@iac.es
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Jon C. Mauerhan (1), Nathan Smith (2), Schuyler D. Van Dyk
(3), Katie M. Morzinski (2), Laird M. Close (2), Philip M. Hinz (2),
Jared R. Males (2), and Timothy J. Rodigas (4)
(1) UC
Berkeley; (2)Steward Observatory; (3) IPAC/Caltech; (4) Carnegie
Institute
NaSt1 (aka Wolf-Rayet 122) is a peculiar
emission-line star embedded in an extended nebula of [N II] emission
with a compact dusty core. This object was characterized by Crowther
& Smith (1999) as a Wolf-Rayet (WR) star cloaked in an opaque
nebula of CNO-processed material, perhaps analogous to Eta Car and
its Homunculus nebula, albeit with a hotter central source. To
discern the
morphology of the [N II] nebula we performed
narrowband imaging using the Hubble Space Telescope and Wide-field
Camera 3. The images reveal that the nebula has a disk-like geometry
tilted 12 degrees from edge-on, composed of a bright central
ellipsoid surrounded by a larger clumpy ring. Ground-based
spectroscopy reveals radial velocity structure (~10 km/s) near the
outer portions of the nebula's major axis, which is likely to be the
imprint of outflowing gas. Near-infrared adaptive-optics imaging with
Magellan AO has resolved a compact ellipsoid of Ks-band emission
aligned with the larger [N II] nebula, which we suspect is the result
of scattered He I line emission (2.06 um). Observations with the
Chandra X-ray Observatory have revealed an X-ray point source at the
core of the nebula that is heavily absorbed at energies <1 keV and
has properties consistent with WR stars and colliding-wind binaries.
We suggest that NaSt1 is a WR binary embedded in an equatorial
outflow that formed as the result of non-conservative mass transfer.
NaSt1 thus appears to be a rare and important example of a
stripped-envelope WR forming through binary interaction, caught in
the brief Roche-Lobe overflow phase.
Reference: MNRAS,
2015, in press
Status: Manuscript has been accepted
Weblink:
http://arxiv.org/abs/1502.01794
Comments:
Email: mauerhan@astro.berkeley.edu
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J.-C. Bouret, T. Lanz, D. J. Hillier,
F. Martins, W. L. F. Marcolino, E. Depagne
1 Aix Marseille
Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille)
UMR 7326, 13388, Marseille, France
2 Laboratoire J.-L. Lagrange,
UMR 7293, Université de Nice-Sophia Antipolis, CNRS, Observatoire de
la Côte d’Azur B.P. 4229, 06304 Nice Cedex 4, France
3
Department of Physics and Astronomy, University of Pittsburgh,
3941O’Hara Street, Pittsburgh, PA 15260, USA
4 LUPM–UMR5299,
Université Montpellier II & CNRS, Place Eug`ene Bataillon,
F-34095 Montpellier Cedex 05, France
5 Universidade Federal do
Rio de Janeiro, Observatório do Valongo. Ladeira Pedro Antônio, 43,
CEP 20080-090, Rio de Janeiro, Brazil
6 South African
Astronomical Observatory (SAAO), Observatory Road Observatory Cape
Town, WC 7925, South
We present a spectroscopic analysis of
HST/COS observations of three massive stars in the low metallicity
dwarf galaxies IC 1613 and WLM. These stars, were previously observed
with VLT/X-shooter by Tramper et al. (2011, 2014) who claimed that
their mass-loss rates are higher than expected from theoretical
predictions for the underlying metallicity. A comparison of the FUV
spectra with those of stars of similar spectral types/luminosity
classes in the Galaxy, and the Magellanic Clouds provides a direct,
model-independent check of the mass-loss - metallicity relation.
Then, a quantitative spectroscopic analysis is carried out using the
NLTE stellar atmosphere code CMFGEN. We derive the photospheric and
wind characteristics, benefiting from a much better sensitivity of
the FUV lines to wind properties than Ha. Iron and CNO abundances are
measured, providing an independent check of the stellar metallicity.
The spectroscopic analysis indicates that Z/Zsun = 1/5, similar to a
SMC-type environment, and higher than usually quoted for IC 1613 and
WLM. The mass-loss rates are smaller than the empirical ones by
Tramper et al. (2014), and those predicted by the widely used
theoretical recipe by Vink et al. (2001). On the other hand, we show
that the empirical, FUV-based, mass-loss rates are in good agreement
with those derived from mass fluxes computed by Lucy (2012). We do
not concur with Tramper et al. (2011, 2014) that there is a breakdown
in the mass-loss - metallicity relation.
Reference:
MNRAS
Status: Manuscript has been accepted
Weblink:
http://arxiv.org/abs/1502.05641
Email:
jean-claude.bouret@lam.fr
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M. Wittkowski (1) and C.
Paladini (2)
(1) ESO, Karl-Schwarzschild-Str. 2, 85748
Garching bei Muenchen, Germany
(2) Institut d'Astronomie et
d'Astrophysique, Universite Libre de Bruxelles, ULB, CP.226,
Boulevard du Triomphe, 1050 Brussels, Belgium
We discuss and
illustrate contributions that optical interferometry has made on our
current understanding of cool evolved stars. We include red giant
branch (RGB) stars, asymptotic giant branch (AGB) stars, and red
supergiants (RSGs). Studies using optical interferometry from visual
to mid-infrared wavelengths have greatly increased our knowledge of
their atmospheres, extended molecular shells, dust formation, and
winds. These processes and the morphology of the circumstellar
environment are important for the further evolution of these stars
toward planetary nebulae (PNe) and core-collapse supernovae (SNe),
and for the return of material to the interstellar
medium.
Reference: To appear in the Book of the VLTI
School 2013, held 9-21 Sep 2013 Barcelonnette (France), "What
the highest angular resolution can bring to stellar astrophysics?",
Ed. Millour, Chiavassa, Bigot, Chesneau, Meilland, Stee, EAS
Publications Series (2015)
Status: Conference
proceedings
Weblink:
Comments:
Email:
mwittkow@eso.org
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Closed Job Offers (original deadline passed)
Raphael Hirschi
Keele University
Astrophysics
Group
School of Physical and Geographical Sciences
Lennard-Jones
Laboratories
Keele
ST5 5BG, UK
The Astrophysics Group
at Keele University has several funded studentships (STFC/Keele
funding) in astronomy/astrophysics to start in September 2015.
Possible projects include (title, main supervisor):
-
Nuclear astrophysics: impact and sensitivity studies, Dr Raphael
Hirschi
- Nucleosynthesis in rotating stars, Dr Raphael Hirschi
- Transiting extra-solar planets with WASP-South, Prof Coel
Hellier
- High-precision studies of eclipsing binary stars
observed using space telescopes (Southworth)
- Laboratory
astrophysics at the Diamond Light Source, Prof Nye Evans
- Star
formation and stellar ages from the Gaia-ESO Spectroscopic Survey
(Prof. R. D. Jeffries)
- Outer solar system chemistry (Dr Jacco
van Loon, Prof. A. Evans)
- Star formation in the Magellanic
Clouds (Dr. Joana Oliveira)
- Atmospheric properties of A, F and
G stars (Dr Barry Smalley)
Notes: applications open to EU
students (non-EU students can apply for a self-funded PhD position).
More information on the projects, the Keele astrophysics group and
how to apply can be found here:
http://www.keele.ac.uk/researchsubjects/astrophysics/
If you
have questions, please do not hesitate to contact
Dr Raphael
Hirschi
(PhD students coordinator)
Attention/Comments:
Weblink:
http://www.keele.ac.uk/researchsubjects/astrophysics/
Email:
r.hirschi@keele.ac.uk
Deadline: Closing Date 28th
February 2015 (applications received by the deadline will receive
first consideration)
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Open JOB offers
Pierre Royer
Institute of Astrophysics
KU
Leuven
Celestijnenlaan 200D
3001 Leuven
Belgium
We
are looking for a motivated PhD student to join our institute to
pursue a research program aiming at a. producing a reference catalog
of high-resolution stellar spectroscopy from a large amount of data
covering the entire HRD (existing in house), b. model these spectra
and compare them with the observations in order to critically assess
the quality of existing databases of fundamental atomic
parameters.
Attention/Comments: Online application
only. For additional information, contact Dr. Katrijn Clémer, tel.:
+32 16 32 70 40, mail: katrijn.clemer@ster.kuleuven.be
Weblink:
http://www.kuleuven.be/solliciteren/53255289&taal=E&type=VA
Email:
pierre.royer@ster.kuleuven.be
Deadline: 15 April
2015
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Leen Decin
Institute
of Astronomy, Leuven University
Celestijnenlaan 200D
B-3001
Heverlee (Leuven)
Belgium
Interdisciplinary project on the
stellar winds around evolved stars at the Leuven University in
Belgium funded by the ERC-CoG 2014 grant AEROSOL (PI. L. Decin).
The project
At the Leuven University (Belgium), we
seek candidates for two post-doctoral and two PhD research positions,
ready to play a key role in a new interdisciplinary project focusing
on stellar winds around evolved (low-mass) stars. The candidates will
interact closely with a team consisting of astrophysicists, chemists,
and computational mathematicians, as the goal of the project is to
boost our understanding of the physics and chemistry characterizing
these stellar winds. The project builds upon novel data (including
ALMA, Herschel, etc.), detailed theoretical wind models, and targeted
laboratory experiments (see
http://fys.kuleuven.be/ster/Projects/aerosol/aerosol).
Institute
of Astronomy
The Institute of Astronomy of the Leuven
University is a young and active research group of some 50
scientists, engineers and administrative staff
(http://www.ster.kuleuven.be). The institute is involved in several
international networks and research projects, involving telescopes at
international observatories and space missions. The institute is also
responsible for the organisation of the Master in Astronomy &
Astrophysics of the Faculty of Science at the Leuven University. The
institute has a long tradition in the observational and theoretical
studies of the late stages of evolution of low and intermediate mass
stars.
For the ERC-CoG AEROSOL project of Prof. L. Decin, we
seek one post-doc and one PhD candidate to work on the reduction,
analysis and (radiative transfer) modeling of a whole suit of
observations ranging from the UV to mm wavelength regime with the aim
to retrieve the geometrical, thermodynamical and chemical structures
of stellar winds. The post-doc preferentially has experience with
infrared and (sub)millimeter observations and has in any case
sufficient experience in implementing and exploiting radiative
transfer models. The post-doc will also be allowed to carry out
(part-time) his/her own research in collaboration with affiliated
group members. The successful candidates will have access to recently
obtained and granted observational data, advanced radiative transfer
and forward chemistry modeling tools and will have the possibility to
develop their own (hydro)simulations.
Physical Chemistry
As
part of this project, one post-doc and one PhD position is open in
the research group of Prof. S. Carl in the field of experimental
gas-phase reaction kinetics in the Department of Chemistry, division
of Quantum and Physical chemistry, beginning preferably on 1st
October 2015. The experimental work will be carried out in the modern
and fully-equipped new research laboratories of the Department of
Chemistry, opening in mid 2015. The experimental research concerns
the determination of rate coefficients and product distributions of
elementary gas-phase reactions involving key reactive species (Si-
and S-bearing species and HCCO radicals) in stellar winds for which
data is currently lacking. Specifically, several advanced
laser-spectroscopic and chemiluminescence techniques will be employed
by the PhD student to follow photolytically-generated reactive
species in real time in a novel temperature-graded reaction vessel
(200−900 K) coupled with cavity-ringdown/Fourier-transform infrared
spectroscopy to elucidate reaction product channels. The post-doc
will concentrate on the construction and exploitation of a novel
low-temperature Laval-nozzle apparatus with the aim to obtain the
rates of the same gas-phase reactions at temperatures below 200 K.
Candidates should have an interest in physical chemistry,
high-resolution laser spectroscopy, and technical experimentation.
The group currently enjoys and encourages further close collaboration
with researches in the department employing high-level quantum
chemical calculations on species related to this project.
The
position
At the Leuven University, the candidates will join
the Institute for Astronomy (Prof. L. Decin) or the Physical
Chemistry section (Prof. S. Carl). The interdisciplinary project is
carried out in collaboration with Prof. T. Millar (Belfast
University) and Prof. J. Nuth (NASA, Greenbelt). The four candidates
will interact closely with the other team members at the Institute of
Astronomy and Department of Chemistry. At the Leuven University, we
have access to parallel computing facilities, to be exploited
extensively in this project.
Contract
The PhD candidates
will be employed for a 2+2 (after positive evaluation) period at the
Institute of Astronomy or a 2+1 period at the Department of
Chemistry. The initial contract for the post-doc positions runs over
2 years and could be prolonged with another year after positive
evaluation. The salary will be commensurate to the standard scale for
PhD and post-doctoral researchers at the Leuven University. The
preferred starting date is between 1 October 2015 and 1 December
2015, but will be adapted to the selected candidate’s availability.
Candidates are thus requested to indicate their preferred starting
date in the application.
Interested?
The successful
post-doc candidates must have a PhD degree in astrophysics or
chemistry, while the PhD candidates must have obtained a master
degree in (astro)physics, mathematics or chemistry. The application
must include
• A Curriculum Vitae (including publication list).
• A statement of research interests and future plans (maximum 3
pages).
• A letter detailing your specific qualifications for
the position and your career/educational goals (maximum 1 page).
•
Two letters of recommendation from professors well acquainted with
your academic achievements. The letters are to be submitted
separately to the address mentioned below.
DEADLINE for the
application: 1 May 2015
More information can be obtained by
contacting
Prof. L. Decin
Institute for Astronomy
Department
of Physics and Astronomy, KU Leuven
Celestijnenlaan 200D, 3001
Heverlee, Belgium
Leen.Decin@ster.kuleuven.be
++32-16-32 70
41
http://fys.kuleuven.be/ster/staff/senior-staff/leen
See
also: http://www.fys.kuleuven.be/ster/
Prof. S. Carl
Physical Chemistry Section
Department of Chemistry, KU Leuven
Celestijnenlaan 200F, 3001 Heverlee, Belgium
Shaun.Carl@chem.kuleuven.be
++32-16-32 76
13
Attention/Comments:
Weblink:
http://fys.kuleuven.be/ster/vacancies
Email:
Leen.Decin@ster.kuleuven.be
Deadline: 01/05/2015
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6-10 July, 2015
Venue: ESO Garching,
Germany
Goals of the Workshop
In this workshop, we
intend to bring together observers and theorists from the low mass
and high mass stellar communities with the goals of:
understanding
the evolved star mass loss process and the injection of energy and
matter (enriched in molecules and dust) into the ISM
comparing
Asymptotic Giant Branch and Red Supergiant stars – why are they
observationally similar in many ways yet apparently have very
different interior stellar structures and their mass loss evolves
differently
determining the roles of magnetic fields, binarity,
jets and collimated mass loss, metallicity, initial mass etc. upon
stellar evolution and end products - how can almost spherically
symmetric stars produce broadly bipolar morphologies over such a
large mass loss range?
The meeting will be spread over five
days, starting on Monday afternoon and ending on Friday at lunchtime.
It will consist of invited and contributed talks, posters and
discussion sessions.
Conference email: steps@eso.org
Important dates:
6 April: abstract submission deadline
15 April: preliminary program
1 May: notification of
contributed talk
4 May: hotel block bookings expire
6 June:
registration payment deadline
6 July: meeting starts
Weblink:
http://www.eso.org/sci/meetings/2015/STEPS2015.html
Email:
steps@eso.org
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1-5 June 2015
Venue: NC State University,
Raleigh, NC, USA
The conference will cover topic related to
supernovae and supernova remnants, broadly addressing the three main
questions:
- Where do supernovae come from?
- How do they
explode?
- What do they leave behind?
There will be
invited talks that will give a broader overview on a topic. In
addition, we will have contributed talks and poster presentations. We
plan to have a grand debate and a panel discussion. We strongly
encourage young researchers to attend. We shall try to accommodate as
many contributed talks as possible but cannot guarantee speaking
slots.
Registration is now open on the website:
http://www.physics.ncsu.edu/FOE2015/
*Deadline for abstract
submission is 15 April 2015*
A preliminary schedule will
apprear around the end of April/beginning of May.
*Registration
deadline is 30 April 2015.*
Conference info together with the
important dates and housing information can be found on the website:
http://www.physics.ncsu.edu/FOE2015/
Weblink:
http://www.physics.ncsu.edu/FOE2015/
Email:
fifty-one_ergs@ncsu.edu
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contents
23rd to 28th August 2015
Venue: University of
St Andrews, UK
A summer school on Monte Carlo radiation
transfer techniques will be held at the University of St Andrews, UK
from 23rd to 28th August 2015. The course is limited to thirty
students, with priority given to STFC-funded PhD students and
postdocs.
Students will be introduced to the basic techniques
in Monte Carlo radiation transfer and their applications to scattered
light, dust and gas radiative equilibrium, photoionization, and NLTE
molecular line transfer. Several publicly available Monte Carlo codes
will be introduced in detail with the goal that by the end of the
school the students will have a toolbox of codes that they can use in
their own astrophysical research projects. The program will comprise
short introductory lectures to each topic, followed by detailed
descriptions of individual codes. Lots of time will be set aside for
students to become familiar with using the codes and interacting with
the lecturers who developed them.
Further information,
including details of how to register, can be found here:
http://www-star.st-and.ac.uk/samcss
Weblink:
http://www-star.st-and.ac.uk/samcss
Email:
kw25@st-andrews.ac.uk
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22 June 2015
Venue: La Laguna, Tenerife,
Canary Islands, Spain
Dear colleagues,
We are pleased
to announce the EWASS 2015 Special Session #7
Science with
large spectroscopic surveys of Galactic OB stars: getting ready for
Gaia
to be held in La Laguna, Tenerife, Spain on Monday 22
June 2015
Feel free to share this announcement with anybody
who may be interested on this topic
Deadline for abstract
submission: 10 March 2015
Deadline for early registration: 30
April 2015
See the EWASS2015 webpage
(http://eas.unige.ch/EWASS2015/index.jsp) for more info about
registration, abstract submission, and the complete programme for the
European Week of Astronomy and Space Science 2015
Aims and
scope
In the last decade, several spectroscopic surveys of
Galactic OB stars have been conducted independently by different
groups (GOSSS, OWN, IACOB, CAFE-BEANS, NoMaDs, GES, MiMeS, BOB). The
scientific exploitation of this unique observational material, using
the most modern tools, is currently under way and will without any
doubt quantitatively change our view of the properties (temperature,
gravities, abundances...) and evolution of massive stars. However,
the picture will not be complete until we have access to accurate
distances (hence being able to compute luminosities, stellar radii,
masses, and ages).
The Gaia mission will provide the needed
key to open the frontiers of a new era in the study of Galactic OB
stars. Successfully launched in 2013 december 19, the first data
release (not yet including distances) is planned for summer 2016.
Hence time is ripe to:
(a) establish synergies between the
various on-going spectroscopic surveys of Galactic OB stars;
(b)
discuss the best strategy to share all available observational
information about Galactic OB stars in preparation for the Gaia era;
(c) identify the best tools to extract information about
rotation, stellar and wind parameters and abundances from large
samples of Galactic OB stars; and
(d) identify the interplay
between current spectroscopic surveys and Gaia in the context of the
understanding of massive stars properties and evolution.
This
special session aims at gathering experts in observations, analysis,
and modelling of massive OB stars and key speakers involved in the
Gaia mission with this scope.
Programme
- Modern
tools and techniques for the investigation of Galactic OB stars
-
Past, on-going, and future surveys of Galactic OB stars: getting
ready for Gaia
- Open questions in our knowledge of Galactic OB
stars in the Gaia context
Both contributed talks and posters
are foreseen
Invited speakers
- Y. Frémat (Royal
Observatory of Belgium)
- J. Maíz Apellániz (Astrobiology
Centre, Spain)
- G. Meynet (University of Geneva, Switzerland)
-
J. Puls ( Munich University Observatory, Germany)
- F.N.R.
Schneider (University of Oxford, UK)
- M.A. Urbaneja (University
of Innsbruck, Austria)
We are looking forward to receiving
your abstracts!
The organizers
S. Simón-Díaz (IAC,
Spain) & F. Martins (LUPM, France)
Weblink:
http://eas.unige.ch/EWASS2015/session.jsp?id=Sp7
Email:
ssimon@iac.es
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Aug 3-5, 2015
Venue: Honolulu,
USA
Despite their significance in the massive star life-cycle,
Red Supergiants are arguably the least well-understood class of
massive stars. This is largely due to historical reasons: massive
star research has tended to focus on hot stars, such as O stars and
Wolf-Rayets. At the 2015 IAU-GA we aim to bring together the leading
researchers in the fields of massive stars, cool stars, and
supernovae, to discuss the latest observational and theoretical
advances, and to encourage and stimulate further cross-disciplinary
collaboration.
Topics to be discussed at the meeting:
*
The evolution of massive stars
* The physics of cool stellar
atmospheres, and quantitative spectroscopy
* Spatially resolved
observations of cool stars
* Simulations and observations of
stellar convection
* Mass-loss processes in cool stars
* The
progenitors of supernovae
Weblink:
http://astronomy2015.org/focus_meeting_16
Email:
b.davies@ljmu.ac.uk
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5-7 May 2015
Venue: Royal Observatory of
Belgium, Brussels, Belgium
This is a reminder about this
workshop, which will take place in a few months. Deadline for
abstract submission is 1 March!
Thanks to projects such as
the ongoing Gaia-ESO Survey (GES) and the VLT-Flames Tarantula Survey
(VFTS) progress in the number of massive stars with accurate
parameters is rapidly growing.
In order to bring together the
European expertise in massive-star spectral analysis and evolution it
is timely to organise a Workshop on massive stars in the context of
the Gaia-ESO Survey.
By the time of the meeting about
two-thirds of the GES data will have been collected. The data
reduction and analysis techniques will have been refined to handle
these data and produce significant science output.
One aim of
the workshop is to present the GES results to a wider community of
massive-star experts. The interaction between the various European
massive-star groups will allow us to extract the best science from
the GES data. A second purpose is to interact with the other GES
Co-Is to provide them with the information they need related to e.g.
cluster studies. Finally, it is a timely moment to measure the
progress we have made in achieving the science cases listed in the
GES proposal and to address future directions.
Weblink:
http://ges-ms.oma.be
Email:
Ronny.Blomme@oma.be
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