ISSN 1783-3426

THE MASSIVE STAR NEWSLETTER

formerly known as the hot star newsletter

*

No. 159

2017 May-June

editors: Philippe Eenens (University of Guanajuato)

eenens@gmail.com

Raphael Hirschi (Keele University)

http://www.astroscu.unam.mx/massive_stars

Jose Groh (Trinity College Dublin)





CONTENTS OF THIS NEWSLETTER:

News

Fizeau exchange visitors program - call for applications

Abstracts of 9 accepted papers

Coupling hydrodynamics with comoving frame radiative transfer: I. A unified approach for OB and WR stars
Partial Mixing in Early-Type Main-Sequence B Stars
Gas kinematics in massive star-forming regions from the Perseus spiral arm
Dust dynamics and evolution in HII regions - II. Effects of dynamical coupling between dust and gas
Mid-infrared observations of O-type stars: spectral morphology
The Structure of the Young Star Cluster NGC 6231. I. Stellar Population
The Luminous Blue Variable RMC 127 as Seen with ALMA and ATCA
Investigating the origin of cyclical wind variability in hot, massive stars - II. Hydrodynamical simulations of co-rotating interaction regions using realistic spot parameters for the O giant $\xi$ Persei
Mass loss rates from mid-IR excesses in LMC and SMC O stars

Abstracts of 2 conference proceedings

The Evolution of Massive Stars: Bridging the Gap in the Local Group
Observed properties of red supergiant and massive AGB star populations

Closed Jobs

Postdoctoral Research Position in Time-Domain Astrophysics
1 Postdoc and 2 PhD positions at KU Leuven, Belgium

Meetings

Stars with a stable magnetic field: from pre-main sequence to compact remnants (second announcement)


News

Fizeau exchange visitors program - call for applications



Dear colleagues!

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), with priority given to PhD students and young postdocs. 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 June 15. Fellowships can be awarded for missions to be carried out between August and November 2017!

Further informations and application forms can be found at
www.european-interferometry.eu

The program is funded by OPTICON/H2020.

Please distribute this message also to potentially interested colleagues outside of your community!

Looking forward to your applications,
Josef Hron & Peter Abraham
(for the European Interferometry Initiative)

Weblink: www.european-interferometry.eu

Email: fizeau@european-interferometry.eu

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PAPERS

Abstracts of 9 accepted papers

Coupling hydrodynamics with comoving frame radiative transfer: I. A unified approach for OB and WR stars


Andreas A.C. Sander, Wolf-Rainer Hamann, Helge Todt, Rainer Hainich, Tomer Shenar

Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Str. 24/25, D-14476 Potsdam, Germany

CONTEXT: For more than two decades, stellar atmosphere codes have been used to derive the stellar and wind parameters of massive stars. Although they have become a powerful tool and sufficiently reproduce the observed spectral appearance, they can hardly be used for more than measuring parameters. One major obstacle is their inconsistency between the calculated radiation field and the wind stratification due to the usage of prescribed mass-loss rates and wind-velocity fields.
AIMS: We present the concepts for a new generation of hydrodynamically consistent non-local thermodynamical equilibrium (non-LTE) stellar atmosphere models that allow for detailed studies of radiation-driven stellar winds. As a first demonstration, this new kind of model is applied to a massive O star.
METHODS: Based on earlier works, the PoWR code has been extended with the option to consistently solve the hydrodynamic equation together with the statistical equations and the radiative transfer in order to obtain a hydrodynamically consistent atmosphere stratification. In these models, the whole velocity field is iteratively updated together with an adjustment of the mass-loss rate.
RESULTS: The concepts for obtaining hydrodynamically consistent models using a comoving-frame radiative transfer are outlined. To provide a useful benchmark, we present a demonstration model, which was motivated to describe the well-studied O4 supergiant Zeta Pup. The obtained stellar and wind parameters are within the current range of literature values.
CONCLUSIONS: For the first time, the PoWR code has been used to obtain a hydrodynamically consistent model for a massive O star. This has been achieved by a profound revision of earlier concepts used for Wolf-Rayet stars. The velocity field is shaped by various elements contributing to the radiative acceleration, especially in the outer wind. The results further indicate that for more dense winds deviations from a standard beta-law occur.

Reference: A&A, in press
Status: Manuscript has been accepted

Weblink: https://arxiv.org/abs/1704.08698

Comments: 14 pages, 9 figures

Email: ansander@uni-potsdam.de

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Partial Mixing in Early-Type Main-Sequence B Stars


E.I. Staritsin

K.A. Barkhatova Kourovka Astronomical Observatory, B.N. Yeltsin Ural Federal University, pr. Lenina 51, Ekaterinburg, 620000 Russia

Abstract—Partial mixing of material in the radiative envelopes and convective cores of rotating main sequence stars with masses of 8 and 16 M$_\odot$ is considered as a function of the inital angular momentum of the stars. Losses of rotational kinetic energy to the generation of shear turbulence in the radiative envelope and the subsequent mixing of material in the envelope are taken into account. With an initial equatorial rotational velocity of 100 km/s, partial mixing develops in the upper part of the layer with variable chemical composition and the lower part of the chemically homogeneous radiative envelope. When the initial equatorial rotational velocity is 150–250 km/s, the joint action of shear turbulence and semi-convection leads to partial mixing in the radiative envelope and central parts of the star. The surface abundance of helium is enhanced, with this effect increasing with the angular momentum of the star. With an initial equatorial rotational velocity of 250 km/s, the ratio of the surface abundances of helium and hydrogen grows by $\sim30\%$ and $\sim70\%$ toward the end of the main-sequence evolution of an 8 M$_\odot$ and 16 M$_\odot$ star, respectively. The transformation of rotational kinetic energy into the energy of partial mixing increases with the angular momentum of the star, but does not exceed $\sim2\%−3\%$ in the cases considered.

Reference: Astronomy Reports
Status: Manuscript has been accepted

Weblink:

Comments:

Email: Evgeny.Staritsin@urfu.ru

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Gas kinematics in massive star-forming regions from the Perseus spiral arm


M.S. Kirsanova$^1$, A.M. Sobolev$^2$, M. Thomasson$^3$

$^1$Institute of Astronomy, Russian Academy of Sciences, Moscow, Russia, $^2$ Ural Federal University, Ekaterinburg, Russia , $^3$ Department of Earth and Space Sciences, Chalmers University of Technology, Onsala Space Observatory, Onsala, Sweden

We present results of a survey of 14 star-forming regions from the Perseus spiral arm in CS(2-1) and 13CO(1-0) lines with the Onsala Space Observatory 20 m telescope. Maps of 10 sources in both lines were obtained. For the remaining sources a map in just one line or a single-point spectrum were obtained. On the basis of newly obtained and published observational data we consider the relation between velocities of the "quasi-thermal" CS(2-1) line and 6.7 GHz methanol maser line in 24 high-mass star-forming regions in the Perseus arm. We show that, surprisingly, velocity ranges of 6.7 GHz methanol maser emission are predominantly red-shifted with respect to corresponding CS(2-1) line velocity ranges in the Perseus arm. We suggest that the predominance of the "red-shifted masers" in the Perseus arm could be related to the alignment of gas flows caused by the large-scale motions in the Galaxy. Large-scale galactic shock related to the spiral structure is supposed to affect the local kinematics of the star-forming regions. Part of the Perseus arm, between galactic longitudes from 85deg to 124deg, does not contain blue-shifted masers at all. Radial velocities of the sources are the greatest in this particular part of the arm, so the velocity difference is clearly pronounced. 13CO(1-0) and CS(2-1) velocity maps of G183.35-0.58 show gas velocity difference between the center and the periphery of the molecular clump up to 1.2 km/s. Similar situation is likely to occur in G85.40-0.00. This can correspond to the case when the large-scale shock wave entrains the outer parts of a molecular clump in motion while the dense central clump is less affected by the shock.

Reference: Astronomy reports, accepted
Status: Manuscript has been accepted

Weblink: https://arxiv.org/abs/1705.02197

Comments:

Email: kirsanova@inasan.ru

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Dust dynamics and evolution in HII regions - II. Effects of dynamical coupling between dust and gas


V. V. Akimkin, M. S. Kirsanova, Ya. N. Pavlyuchenkov, D. S. Wiebe

Institute of Astronomy of the Russian Academy of Sciences, 48 Pyatnitskaya St., 119017, Moscow, Russia

In this paper, we extend the study initiated in PaperI by modelling grain ensemble evolution in a dynamical model of an expanding HII region and checking the effects of momentum transfer from dust to gas. The radiation pressure on the dust, the dust drift, and the lug on the gas by the dust are all important process that should be considered simultaneously to describe the dynamics of HII regions. With accounting for the momentum transfer from the dust to the gas, the expansion time of the HII region is notably reduced (for our model of RCW120, the time to reach the observed radius of the HII region is reduced by a factor of 1.5). Under the common approximation of frozen dust, where there is no relative drift between the dust and gas, the radiation pressure from the ionizing star drives the formation of the very deep gas cavity near the star. Such a cavity is much less pronounced when the dust drift is taken into account. The dust drift leads to the two-peak morphology of the dust density distribution and significantly reduces the dust-to-gas ratio in the ionized region (by a factor of 2 to 10). The dust-to-gas ratio is larger for higher temperatures of the ionizing star since the dust grains have a larger electric charge and are more strongly coupled to the gas.

Reference: MNRAS, accepted
Status: Manuscript has been accepted

Weblink: https://arxiv.org/abs/1705.00269

Comments:

Email: kirsanova@inasan.ru

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Mid-infrared observations of O-type stars: spectral morphology


Wagner L. F. Marcolino (1), Jean-Claude Bouret (2), Thierry Lanz (3), Donavan S. Maia (1), Marc Audard (4)

(1) Observatório do Valongo, Universidade Federal do Rio de Janeiro, Brazil
(2) Aix Marseille Univ, CNRS, LAM, Laboratoire d'Astrophysique de Marseille, Marseille, France
(3) Observatoire de la Côte d'Azur, Nice, France
(4) Department of Astronomy, University of Geneva, ch. d'Ecogia 16, CH-1290 Versoix, Switzerland

We present mid-infrared observations for a sample of 16 O-type stars. The data were acquired with the NASA Spitzer Space Telescope, using the IRS instrument at moderate resolution (R ∼ 600), covering the range ∼10−37 microns. Our sample includes early, mid and late O supergiants and dwarfs. We explore for the first time their mid-IR spectral morphology in a quantitative way. We use NLTE expanding atmosphere models to help with line identifications, analyze profile contributions and line-formation regions. The O supergiants present a rich emission line spectra. The most intense features are from hydrogen - 6α, 7α, and 8α - which have non-negligible contributions of HeI or HeII lines, depending on the spectral type. The spectrum of early O supergiants is a composite of HI and HeII lines, HeI lines being absent. On the other hand, late O supergiants present features composed mainly by HI and HeI lines. All emission lines are formed throughout the stellar wind. We found that O dwarfs exhibit a featureless mid-IR spectrum. Two stars of our sample exhibit very similar mid-IR features, despite having a very different optical spectral classification. The analysis of O-type stars based on mid-IR spectra alone to infer spectral classes or to estimate physical parameters may thus be prone to substantial errors. Our results may therefore inform spectroscopic observations of massive stars located in heavily obscured regions and help establish an initial framework for observations of massive stars using the Mid-Infrared Instrument on the James Webb Space Telescope.

Reference: MNRAS
Status: Manuscript has been accepted

Weblink: https://arxiv.org/abs/1705.04244

Comments:

Email: wagner@astro.ufrj.br

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The Structure of the Young Star Cluster NGC 6231. I. Stellar Population


Michael A. Kuhn$^{1,2}$, Nicol\'as Medina$^{1,2}$, Konstantin V. Getman$^{3}$, Eric D. Feigelson$^{3,1}$, Mariusz Gromadzki$^{4,1,2}$, Jordanka Borissova$^{1,2}$, Radostin Kurtev$^{1,2}$

1 - Millennium Institute of Astrophysics, Vicu\~na Mackenna 4860, 7820436 Macul, Santiago, Chile; 2 - Instituto de Fisica y Astronom\'{i}a, Universidad de Valpara\'{i}so, Gran Breta\~{n}a 1111, Playa Ancha, Valpara\'{i}so, Chile; 3 - Department of Astronomy \& Astrophysics, 525 Davey Laboratory, Pennsylvania State University, University Park, PA 16802, USA; 4 - Warsaw University Astronomical Observatory, Al. Ujazdowskie 4, 00-478 Warszawa, Poland

NGC~6231 is a young cluster (age $\sim$2--7~Myr) dominating the Sco~OB1 association (distance $\sim$1.59~kpc) with $\sim$100 O and B stars and a large pre--main-sequence stellar population. We combine a reanalysis of archival {\it Chandra} X-ray data with multi-epoch NIR photometry from the VVV survey and published optical catalogs to obtain a catalog of 2148 probable cluster members. This catalog is 70\% larger than previous censuses of probable cluster members in NGC~6231, and it includes many low-mass stars detected in the NIR but not in the optical and some B-stars without previously noted X-ray counterparts. In addition, we identify 295 NIR variables, about half of which are expected to be pre--main-sequence stars. With the more-complete sample, we estimate a total population in the {\it Chandra} field of 5700--7500 cluster members down to 0.08~$M_\odot$ (assuming a universal initial mass function) with a completeness limit at 0.5~$M_\odot$. A decrease in stellar X-ray luminosities is noted relative to other younger clusters. However, within the cluster, there is little variation in the distribution of X-ray luminosities for ages less than 5~Myr. X-ray spectral hardness for B stars may be useful for distinguishing between early-B stars with X-rays generated in stellar winds and B-star systems with X-rays from a pre--main-sequence companions ($>$35\% of B stars). A small fraction of catalog members have unusually high X-ray median energies or reddened near-infrared colors, which might be explained by absorption from thick or edge-on disks or being background field stars.

Reference: AJ (in press)
Status: Manuscript has been accepted

Weblink: https://arxiv.org/abs/1706.00017

Comments: Electronic tables 1, 3, and 4 are available from http://astro.psu.edu/mystix.

Email: michael.kuhn@uv.cl

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The Luminous Blue Variable RMC 127 as Seen with ALMA and ATCA


C. Agliozzo (1,2), C. Trigilio (3), G. Pignata (2,1) , N. M. Phillips (4,5), R. Nikutta (6,7), P. Leto (3), G. Umana (3), A. Ingallinera (3), C. Buemi (3), F. E. Bauer (1,7,8), R. Paladini (9), A. Noriega-Crespo (10), J. L. Prieto (1,11), M. Massardi (12), and L. Cerrigone (13)

1) Millennium Institute of Astrophysics (MAS), Nuncio Monseñor Sótero Sanz 100, Providencia, Santiago, Chile;
2) Departamento de Ciencias Fisicas, Universidad Andres Bello, Avda. Republica 252, Santiago, 8320000, Chile
3) INAF-Osservatorio Astrofisico di Catania, Via S. Sofia 78, I-95123, Catania Italy
4) European Southern Observatory, Alonso de Córdova 3107, Vitacura, Santiago, Chile
5) Joint ALMA Observatory, Alonso de Córdova 3107, Vitacura, Santiago, Chile
6) National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719, USA
7) Instituto de Astrofísica and Centro de Astroingeniería, Facultad de Física, Pontificia Universidad Católica de Chile, Casilla 306, Santiago 22, Chile
8) Space Science Institute, 4750 Walnut Street, Suite 205, Boulder, CO 80301, USA
9) Infrared Processing Analysis Center, California Institute of Technology, 770 South Wilson Avenue, Pasadena, CA 91125, USA
10) Space Telescope Science Institute, Space Telescope Science Institute 3700 San Martin Drive, Baltimore, MD 21218, USA
11) Núcleo de Astronomía de la Facultad de Ingeniería, Universidad Diego Portales, Av. Ejercito 441, Santiago, Chile
12) INAF-Istituto di Radioastronomia, via Gobetti 101, I-40129, Bologna, Italy
13) ASTRON, Oude Hoogeveensedijk 4, 7991 PD, Dwingeloo, The Netherlands

We present ALMA and ATCA observations of the luminous blue variable RMC 127. The radio maps show for the first time the core of the nebula and evidence that the nebula is strongly asymmetric with a Z-pattern shape. Hints of this morphology are also visible in the archival \emph{HST} $\rm H\alpha$ image, which overall resembles the radio emission. The emission mechanism in the outer nebula is optically thin free-free in the radio. At high frequencies, a component of point-source emission appears at the position of the star, up to the ALMA frequencies. The rising flux density distribution($S_{\nu}\sim\nu^{0.78\pm0.05}$) of this object suggests thermal emission from the ionized stellar wind and indicates a departure from spherical symmetry with $n_{e}(r)\propto r^{-2}$. We examine different scenarios to explain this excess of thermal emission from the wind and show that this can arise from a bipolar outflow, supporting the suggestion by other authors that the stellar wind of \rmc is aspherical. We fit the data with two collimated ionized wind models and we find that the mass-loss rate can be a factor of two or more smaller than in the spherical case. We also fit the photometry obtained by IR space telescopes and deduce that the mid- to far-IR emission must arise from extended, cool ($\sim80\,\rm K$) dust within the outer ionized nebula. Finally we discuss two possible scenarios for the nebular morphology: the canonical single star expanding shell geometry, and a precessing jet model assuming presence of a companion star.

Reference: ApJ, published online
Status: Manuscript has been accepted

Weblink: http://iopscience.iop.org/article/10.3847/1538-4357/aa72a1/meta

Comments:

Email: c.agliozzo@gmail.com

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Investigating the origin of cyclical wind variability in hot, massive stars - II. Hydrodynamical simulations of co-rotating interaction regions using realistic spot parameters for the O giant $\xi$ Persei


Alexandre David-Uraz (1,2,3), Stan P. Owocki (4), Gregg A. Wade (1), Jon O. Sundqvist (5,6), N. Dylan Kee (4,7)

(1) Department of Physics, Royal Military College of Canada, PO Box 17000, Stn Forces, Kingston, Canada, K7K 4B4 (2) Department of Physics, Engineering Physics and Astronomy, Queen’s University, 99 University Avenue, Kingston, Canada, K7L 3N6 (3) Department of Physics & Space Sciences, Florida Institute of Technology, Melbourne, FL 32901, USA (4) Bartol Research Institute, University of Delaware, Newark, DE 19716, USA (5) Centro de Astrobiologia, CSIC-INTA, Ctra. Torrejon a Ajalvir km. 4, E-28850 Madrid, Spain (6) Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200D, B-3001 Leuven, Belgium (7)Institut fuer Astronomie und Astrophysik, Universitaet Tuebingen, Auf der Morgenstelle 10, D-72076 Tuebingen, Germany

OB stars exhibit various types of spectral variability historically associated with wind structures, including the apparently ubiquitous discrete absorption components (DACs). These features have been proposed to be caused either by magnetic fields or non-radial pulsations. In this second paper of this series, we revisit the canonical phenomenological hydrodynamical modelling used to explain the formation of DACs by taking into account modern observations and more realistic theoretical predictions. Using constraints on putative bright spots located on the surface of the O giant $\xi$ Persei derived from high precision space-based broadband optical photometry obtained with the Microvariability and Oscillations of STars (MOST) space telescope, we generate two-dimensional hydrodynamical simulations of co-rotating interaction regions in its wind. We then compute synthetic ultraviolet (UV) resonance line profiles using Sobolev Exact Integration and compare them with historical timeseries obtained by the International Ultraviolet Explorer (IUE) to evaluate if the observed behaviour of $\xi$ Persei's DACs is reproduced. Testing three different models of spot size and strength, we find that the classical pattern of variability can be successfully reproduced for two of them: the model with the smallest spots yields absorption features that are incompatible with observations. Furthermore, we test the effect of the radial dependence of ionization levels on line driving, but cannot conclusively assess the importance of this factor. In conclusion, this study self-consistently links optical photometry and UV spectroscopy, paving the way to a better understanding of cyclical wind variability in massive stars in the context of the bright spot paradigm.

Reference: To appear in MNRAS Main Journal
Status: Manuscript has been accepted

Weblink: http://arxiv.org/abs/1706.03647

Comments: 16 pages, 10 figures

Email: adu@udel.edu

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Mass loss rates from mid-IR excesses in LMC and SMC O stars


D. Massa
A.W. Fullerton
R.K. Prinja


Space Science Institute
STScI
UCL

We use a combination of BVJHK and Spitzer [3.6], [5.8] and [8.0] photometry to determine IR excesses for a sample of 58 LMC and 46 SMC O stars. This sample is ideal for determining IR excesses because the very small line of sight reddening minimizes uncertainties due to extinction corrections. We use the core-halo model developed by Lamers & Waters (1984a) to translate the excesses into mass loss rates and demonstrate that the results of this simple model agree with the more sophisticated CMFGEN models to within a factor of 2. Taken at face value, the derived mass loss rates are larger than those predicted by Vink et al. (2001), and the magnitude of the disagreement increases with decreasing luminosity. However, the IR excesses need not imply large mass loss rates. Instead, we argue that they probably indicate that the outer atmospheres of O stars contain complex structures and that their winds are launched with much smaller velocity gradients than normally assumed. If this is the case, it could affect the theoretical and observational interpretations of the ``weak wind'' problem, where classical mass loss indicators suggest that the mass loss rates of lower luminosity O stars are far less than expected.

Reference: MNRAS in press
Status: Manuscript has been accepted

Weblink:

Comments:

Email: dmassa@spacescience.org

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Abstracts of 2 conference proceedings

The Evolution of Massive Stars: Bridging the Gap in the Local Group


Philip Massey (1), Kathryn F. Neugent (1), and Emily M. Levesque (2)

(1) Lowell Observatory and Dept of Physics and Astronomy, Northern Arizona University, (2) Department of Astronomy, University of Washington

The nearby galaxies of the Local Group can act as our laboratories in helping to bridge the gap between theory and observations. In this review we will describe the complications of identifying samples of OB stars, yellow and red supergiants, and Wolf-Rayet stars, and what we have so far learned from these studies.

Reference: To appear in Philosophical Transactions A, from the conference "Bridging the Gap: from Massive Stars to Supernovae."
Status: Conference proceedings

Weblink: https://arxiv.org/abs/1706.02786

Comments:

Email: phil.massey@lowell.edu

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Observed properties of red supergiant and massive AGB star populations


Jacco Th. van Loon

Lennard Jones Laboratories, Keele University, ST5 5BG, UK

This brief review describes some of the observed properties of the populations of massive asymptotic giant branch (AGB) stars and red supergiants (RSGs) found in nearby galaxies, with a focus on their luminosity functions, mass-loss rates and dust production. I do this within the context of their role as potential supernova (SN) progenitors, and the evolution of SNe and their remnants. The paper ends with an outlook to the near future, in which new facilities such as the James Webb Space Telescope offer a step change in our understanding of the evolution and fate of the coolest massive stars in the Universe.

Reference: Memorie della Societa Astronomica Italiana, eds. Amanda Karakas, Paolo Ventura, Flavia Dell'Agli and Marcella Di Criscienzo
Status: Conference proceedings

Weblink: https://arxiv.org/abs/1706.01729

Comments: Invited review for "The AGB-Supernovae Mass transition" conference held in Rome in March 2017

Email: j.t.van.loon@keele.ac.uk

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CLOSED JOBS

Postdoctoral Research Position in Time-Domain Astrophysics


Dr. Ondrej Pejcha

Institute of Theoretical Physics
Faculty of Mathematics and Physics, Charles University
V Holesovickach 2
180 00 Praha 8
Czech Republic

Applications are invited for a postdoctoral position at the Institute of Theoretical Physics at Charles University in Prague, Czech Republic, to join the research group established through Primus award to Dr. Ondrej Pejcha. We seek candidates in areas connected with transients (supernovae and similar), variable stars, and time-domain astronomy in general (including solar system astronomy). In particular, candidates interested in working with the All-Sky Automated Survey for Supernovae (ASAS-SN) are encouraged to apply.

Applicants must have a PhD in astronomy or a related field by the start date of the appointment. Experience in observational astronomy is preferred, but this position would also be appropriate for a theorist. The appointment will begin in Fall 2017, but the starting date is negotiable. Appointment is initially for one year and extendable for up to three years. The position includes competitive research budget and opportunity for independent research.

Interested applicants are encouraged to contact Dr. Ondrej Pejcha (http://www.astro.princeton.edu/~pejcha/) for details of the project.

Attention/Comments:

Weblink: https://jobregister.aas.org/job_view?JobID=60764

Email: ondrej.pejcha@gmail.com

Deadline: June 30 2017

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1 Postdoc and 2 PhD positions at KU Leuven, Belgium:
The winds of hot and cool massive stars


Leen Decin, Hugues Sana, Jon Sundqvist, Alex de Koter

Institute of Astrophysics, KU Leuven, Celestijnlaan 200D, 3001 Leuven, Belgium

The Institute of Astronomy of the KU Leuven (Belgium) seeks highly motivated and excellent applicants to take on an important role in the MAESTRO project. Applications are invited for 1 postdoc and at least one2 PhD positions financed through a prestigious fundamental research grant (C1) from the KU Leuven university. The selected candidates will join the MAESTRO team, closely under the supervision of with Profs. Leen Decin, Hugues Sana, Jon Sunqvist and Alex de Koter and as part of an international network of collaborators to obtain crucial observational constraints and to develop new theoretical methods needed to progress our understanding of hot and cool massive star winds.

The MAESTRO project will open 6 positions in the next 3 years. Here, we sSpecifically advertise the following 1 postdoc and 2 PhD positions:
- PhD position: Theory of Wolf-Rayet winds – The PhD student will aim to develop a theoretical framework for the radiative acceleration that drives the winds of Wolf-Rayet (WR) stars and obtain theoretical predictions for global wind properties and their scaling with fundamental stellar parameters.

- PhD position: Observations of Red Supergiant winds – The PhD student will aim to derive the geometrical and dynamical wind structure of Red Supergiants (RSGs) using existing retrieval methods and will study the current morphology and mass-loss evolution during the RSG life time, and the mass-loss signatures at low metallicities.

- Postdoc position: Observations of hot and cool massive stars – The postdoc will be responsible for the observational aspects of the MAESTRO projects. Tasks encompass among other: collect, reduce and/or organize a multi-wavelength data-set covering hot (OB, WR) and cool (RSGs) massive stars across a wide metallicity range, develop and/or adapt the necessary techniques to analysis crowded regions and unresolved small clusters. Lead the analysis of these data, include the daily supervision of students in the MAESTRO project.

Attention/Comments: More information on the projects and instruction to apply are to be found on https://fys.kuleuven.be/ster/Projects/maestro

Weblink: https://fys.kuleuven.be/ster/vacancies/maestro-vacancies

Email: Leen.Decin@kuleuven.be

Deadline: Jul 15, 2017

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MEETINGS

Stars with a stable magnetic field: from pre-main sequence to compact remnants (second announcement)


August 28 - September 01, 2017

Venue: Department of Theoretical Physics and Astrophysics, Brno, Czech Republic

The registration is open until the 15th of August at
http://magnetic17.physics.muni.cz/registration/
Abstract submission deadline is the 1st of July.

Information about accommodation is available at
http://magnetic17.physics.muni.cz/location/accommodation/

Scientific Rationale:

Magnetic fields play an important role in the evolution of all stellar objects, through their ability to influence and alter the angular momentum evolution, internal mixing, activity phenomena, surface abundances and mass-loss of stars. This research field benefits from new highly accurate measurements and numerical simulations, enabling stellar astrophysicists to take magnetic fields into account in most models of stellar structure and evolution. We want to bring together researchers from different fields where magnetic fields play an important role to join their efforts and discuss their common interests.

The following topics will be covered:
- Characteristics of surface magnetic fields in early-type stars
- Magnetic fields and the stellar structure and evolution
- Magnetism, accretion and braking of PMS stars
- Surface structure formation in the presence of magnetic field: connection with diffusion and accretion
- Magnetic field origin and stability
- Magnetically-confined winds
- Stellar pulsations in the presence of global magnetic fields
- Post main sequence evolution of early-type magnetic stars
- Final phases of stellar evolution: magnetism in compact objects
- The future of magnetic field measurements in hot stars

The proceedings of the conference will be published in the Contributions of the Astronomical Observatory Skalnate Pleso.

Here is the current list of invited talks:

Introductory review
Impact of magnetic fields on stellar structure and evolution: L. Ferrario, Australia

Session 1- Magnetized stellar formation
Magnetic fields of Giant Molecular Clouds: P. Padoan, Spain
The fossil field theory: models versus observations: K. Augustson, France
Photospheric magnetic geometry and channelled accretion of PMS stars: G. Hussain, ESO
Modelling the magnetized accretion and outflows in young stellar objects: C. Fendt, Germany
The role of turbulence and magnetic fields for star formation: C. Federrath, Australia

Session 2- Magnetic activity including pulsations of upper main-sequence stars and binaries
Numerical simulations of stellar dynamos: G. Guerrero, Brazil (TBC)
Stellar activity and stellar pulsations from ground and space based: TBA
Magnetic fields of intermediate mass objects: P. Petit, France
Surface mapping tools: theories versus observations: O. Kochukhov, Sweden
Asteroseismology of magnetic stars: P. Walczak, Poland
Magnetic fields in binary systems: Y. Naze, Belgium

Session 3- Origin and impact of magnetic fields in massive stars
The dynamo theory: models versus observations: S. Mathis, France
Magnetic fields of massive stars: C. Neiner, France
Modelling complex magnetic fields in stars with radiative envelopes: J. Silvester, Sweden
Magnetic field stability in massive stars: A. Bonanno, Italy
Magnetic confinement, structure and variability of hot-star winds: TBA

Session 4- Magnetic fields in the ultimate stages of stellar evolution
The evolution of magnetic fields from the main-sequence to very late stages: TBA
Magnetic fields of cool giant and supergiant stars: models versus observations: H. Korhonen, Denmark
Magnetic fields of AGB stars and planetary nebulae: models versus observations: W. Vlemmings, Sweden
Magnetic fields of white dwarfs: A. Kawka, Czech Republic
Magnetic fields of neutron stars: A. Reisenegger, Chile (TBC)
Angular momentum evolution of magnetic black holes: B. Mukhopadhyay, India (TBC)

Session 5- The future of magnetic field measurements
The current status of the observational capabilities to characterize magnetic fields: S. Bagnulo, UK (TBC)
Upcoming instruments suitable to measure magnetic fields: G. Wade, Canada
Impact of new instruments and satellite missions: W. Weiss, Austria

Weblink: http://magnetic17.physics.muni.cz/

Email: magnetic17@physics.muni.cz

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