ISSN 1783-3426
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On the Rotation of Supermassive
Stars
BRITE-Constellation reveals
evidence for pulsations in the enigmatic binary eta Carinae
The
magnetic variability of the β Cep star ξ1 CMa
Identifying
two groups of massive stars aligned in the l~38º Galactic
direction
A combined
multiwavelength VLA/ALMA/Chandra study unveils the complex
magnetosphere of the B-type star HR5907
Mapping
the core of the Tarantula Nebula with VLT-MUSE: I. Spectral and
nebular content around R136
Intriguing
X-ray and optical variations of the gamma Cas analog HD45314
The
long-period massive binary HD 54662 revisited
The
life cycles of Be viscous decretion discs: fundamental disc
parameters of 54 SMC Be stars
An
LTE effective temperature scale for red supergiants in the Magellanic
clouds
Postdoctoral Research Assistant -
Stellar Wind modelling
Research
fellow in stellar astrophysics
The gamma-Cas
phenomenon in Be stars
Dwarf
Galaxies: From the Deep Universe to the Present
Dear Members of the G2 Commission,
It is with deep sadness that we have come to learn that one of the giants in our field, our colleague and friend Nolan Walborn, passed away on the night of 21 to 22 february 2018.
Nolan received his PhD from the University of Chicago under the supervision of W.W. Morgan, followed by postdoctoral positions in Toronto and at Cerro Tololo Inter-American Observatory in La Serena. This allowed him to renew his links to the Latin American culture, to which he had strong ties, as he spent several years in Argentina as a child. After Cerro Tololo and a short stint at NASA's Goddard Space Flight Center, he joined the Space Telescope Science Institute in 1984, where he remained working until the very last moment.
He was a very active member of our community and a strong advocate of hot stars, to which he dedicated his professional life with true passion. He always found those objects extremely interesting, and anyone talking to him was immediately caught by his enthusiasm. His pioneering work on spectral properties and classification of hot, massive stars, both in the optical and ultraviolet, are a primary reference and his contributions set a high standard in the field. In recognition of his outstanding contributions, the IAU approved to name Minor Planet 25942 after him.
It is without doubt an immense loss for our community - and we will deeply miss him. Our thoughts and prayers are with his family and his loved ones he left behind during this difficult time.
The Organizing Committee of the Massive Stars Commission
Artemio Herrero, Jorick Vink, Nicole St.-Louis, Asif ud-Doula, You-Hua Chu, Gregor Rauw, Jose Groh
Weblink:
Email:
ahd@iac.es
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Noel D. Richardson, Herbert Pablo, Christiaan Sterken,
Andrzej Pigulski, Gloria Koenigsberger, Anthony F. J. Moffat, Thomas
I. Madura, Kenji Hamaguchi, Michael F. Corcoran, Augusto Damineli,
Theodore R. Gull, D. John Hillier, Gerd Weigelt, Gerald Handler, Adam
Popowicz, Gregg A. Wade, Werner W. Weiss, Konstanze
Zwintz
University of Toledo +
eta Car is a
massive, eccentric binary with a rich observational history. We
obtained the first high-cadence, high-precision light curves with the
BRITE-Constellation nanosatellites over 6 months in 2016 and 6 months
in 2017. The light curve is contaminated by several sources including
the Homunculus nebula and neighboring stars, including the eclipsing
binary CPD−59 2628. However, we found two coherent oscillations in
the light curve. These may represent pulsations that are not yet
understood but we postulate that they are related to tidally excited
oscillations of eta Car's primary star, and would be similar to those
detected in lower-mass eccentric binaries. In particular, one
frequency was previously detected by van Genderen et al. and Sterken
et al. through the time period of 1974 to 1995 through timing
measurements of photometric maxima. Thus, this frequency seems to
have been detected for nearly four decades, indicating that it has
been stable in frequency over this time span. These pulsations could
help provide the first direct constraints on the fundamental
parameters of the primary star if confirmed and refined with future
observations.
Reference: Accepted to MNRAS
Status:
Manuscript has been accepted
Weblink:
https://arxiv.org/abs/1801.05445
Comments:
Email: noel.richardson@UToledo.edu
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S. P. Järvinen (1), S. Hubrig (1), M. Schöller (2), I.
Ilyin (1)
1 - Leibniz-Institut für Astrophysik
Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany
2 - European Southern Observatory, Karl-Schwarzschild-Str. 2,
85748 Garching, Germany
ξ1 CMa is a known magnetic star
showing rotationally modulated magnetic variability with a period of
2.17937 d. However, recent work based on high-resolution
spectropolarimetry suggests that the rotation period is longer than
30 years. We compare our new spectropolarimetric measurements with
FORS 2 at the VLT acquired on three consecutive nights in 2017 to
previous FORS 1/2 measurements of the longitudinal magnetic field
strength. The new longitudinal magnetic field values are in the range
from 115 to 240 G and do not support the presence of a long
period.
Reference: 2018,
New Astronomy, 62, 37
Status: Manuscript has been
accepted
Weblink:
http://cdsads.u-strasbg.fr/abs/2018arXiv180107017J
Comments:
Email: sjarvinen@aip.de
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Ramírez Alegría, S. (1), Herrero, A. (2,3), Rübke, K.
(2,3), Marín-Franch, A. (4), García, M. (5), & Borissova, J.
(6,7)
(1) Unidad de Astronomía, Universidad de
Antofagasta, Chile
(2) Instituto de Astrofísica de Canarias, Spain
(3) Departamento de Física, Universidad de La Laguna, Spain
(4) Centro de Estudios de Física del Cosmos de Aragón (CEFCA), Spain
(5) Centro de Astrobiología, CSIC-INTA, Spain
(6) Instituto de Física y Astronomía, Universidad de Valparaíso,
Chile
(7) Millennium Institute of Astrophysics, Chile
Recent near-infrared data have contributed to unveil massive and obscured
stellar populations in both new and previously known clusters in our
Galaxy. These discoveries lead us to view the Milky Way as an active
star-forming machine. We look for young massive cluster candidates as
over-densities of OB-type stars. The first search, focused on the
Galactic direction l=38º, resulted in the detection of two objects
with a remarkable population of OB-type star candidates. With a
modified version of the friends-of-friends algorithm AUTOPOP and
using 2MASS and UKIDSS-GPS near-infrared (J, H, and K) photometry for
one of our cluster candidates (named Masgomas-6) we selected 30 stars
for multi-object and long-slit H- and K-spectroscopy. With the
spectral classification and the near-infrared photometric data, we
derive individual distance, extinction and radial velocity. Of the 30
spectroscopically observed stars, 20 are classified as massive stars,
including OB-types (dwarfs, giants and supergiants), two red
supergiants, two Wolf-Rayet (WR122-11 and the new WR122-16), and one
transitional object (the LBV candidate IRAS 18576+0341). The
individual distances and radial velocities do not agree with a single
cluster, indicating that we are observing two populations of massive
stars in the same line-of-sight: Masgomas-6a and Masgomas-6b. The
first group of massive stars, located at 3.9 kpc, contains both
Wolf-Rayets and most of the OB-dwarfs, and Masgomas-6b, at 9.6 kpc,
hosts the LBV candidate and an evolved population of supergiants. We
are able to identify massive stars at two Galactic arms, but we can
not clearly identify whether these massive stars form clusters or
associations.
Reference:
https://arxiv.org/abs/1801.08683
Status:
Manuscript has been accepted
Weblink:
https://arxiv.org/abs/1801.08683
Comments:
Email: sebastian.ramirez@uamail.cl
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P. Leto(1), C. Trigilio(1), L.M. Oskinova(2), R.
Ignace(3), C.S. Buemi(1), G. Umana(1), A. Ingallinera(1), F.
Leone(4,1), N.M. Phillips(5,6), C. Agliozzo(5), H. Todt(2), L.
Cerrigone(6,7)
1 - INAF - Osservatorio Astrofisico di
Catania, Via S. Sofia 78, 95123 Catania, Italy
2 - Institute for Physics and Astronomy, University Potsdam, 14476 Potsdam, Germany
3 - Department of Physics & Astronomy, East Tennessee State University, Johnson City, TN 37614, USA
4 - Universita' degli studi di Catania, Via S. Sofia 78, I-95123 Catania, Italy
5 - European Southern Observatory, Alonso de Cordova 3107, Vitacura, Santiago, Chile
6 - Joint ALMA Observatory, Alonso de Cordova 3107, Vitacura, Santiago, Chile
7 - Associated Universities, Inc., Av. Nueva Costanera 4091, Suite 502, Vitacura, Santiago, Chile
We present new radio/millimeter measurements of the hot magnetic star HR5907
obtained with the VLA and ALMA interferometers. We find that HR5907
is the most radio luminous early type star in the cm-mm band among
those presently known. Its multi-wavelength radio light curves are
strongly variable with an amplitude that increases with radio
frequency. The radio emission can be explained by the populations of
the non-thermal electrons accelerated in the current sheets on the
outer border of the magnetosphere of this fast rotating magnetic
star. We classify HR5907 as another member of the growing class of
strongly magnetic fast rotating hot stars where the gyro-synchrotron
emission mechanism efficiently operates in their magnetospheres. The
new radio observations of HR5907 are combined with archival X-ray
data to study the physical condition of its magnetosphere. The X-ray
spectra of HR5907 show tentative evidence for the presence of
non-thermal spectral component. We suggest that non-thermal X-rays
originate a stellar X-ray aurora due to streams of non-thermal
electrons impacting on the stellar surface. Taking advantage of the
relation between the spectral indices of the X-ray power-law spectrum
and the non-thermal electron energy distributions, we perform 3-D
modeling of the radio emission for HR5907. The wavelength-dependent
radio light-curves probe magnetospheric layers at different heights
above the stellar surface. A detailed comparison between simulated
and observed radio light-curves leads us to conclude that the stellar
magnetic field of HR5907 is likely non-dipolar, providing further
indirect evidence of the complex magnetic field topology of
HR5907.
Reference: MNRAS
Status: Manuscript
has been accepted
Weblink:
https://arxiv.org/pdf/1801.08738.pdf
Comments:
Email: c.agliozzo@gmail.com
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N. Castro (1), P. A. Crowther (2), C. J. Evans (3), J.
Mackey (4), N. Castro-Rodriguez (5), J. S. Vink (6), J. Melnick (7),
F. Selman (7)
(1) University of Michigan, (2)
University of Sheffield, (3) UK Astronomy Technology Centre, (4)
Dublin Institute for Advanced Studies, (5) GRANTECAN, (6) Armagh
Observatory and Planetarium, (7) European Southern Observatory
We
introduce VLT-MUSE observations of the central 2′×2′ (30×30 pc)
of the Tarantula Nebula in the Large Magellanic Cloud. The
observations provide an unprecedented spectroscopic census of the
massive stars and ionised gas in the vicinity of R136, the young,
dense star cluster located in NGC 2070, at the heart of the richest
star-forming region in the Local Group. Spectrophotometry and
radial-velocity estimates of the nebular gas (superimposed on the
stellar spectra) are provided for 2255 point sources extracted from
the MUSE datacubes, and we present estimates of stellar radial
velocities for 270 early-type stars (finding an average systemic
velocity of 271±41 km/s). We present an extinction map constructed
from the nebular Balmer lines, with electron densities and
temperatures estimated from intensity ratios of the [SII], [NII], and
[SIII] lines. The interstellar medium, as traced by Hα and [NII]
λ6583, provides new insights in regions where stars are probably
forming. The gas kinematics are complex, but with a clear bi-modal,
blue- and red-shifted distribution compared to the systemic velocity
of the gas centred on R136. Interesting point-like sources are also
seen in the eastern cavity, western shell, and around R136; these
might be related to phenomena such as runaway stars, jets, formation
of new stars, or the interaction of the gas with the population of
Wolf--Rayet stars. Closer inspection of the core reveals red-shifted
material surrounding the strongest X-ray sources, although we are
unable to investigate the kinematics in detail as the stars are
spatially unresolved in the MUSE data. Further papers in this series
will discuss the detailed stellar content of NGC 2070 and its
integrated stellar and nebular properties.
Reference:
ArXiv:1802.01597
Status:
Manuscript has been accepted
Weblink:
https://arxiv.org/abs/1802.01597
Comments:
Email: ncastror@umich.edu
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G. Rauw (1), Y. Naze (1), M.A. Smith (2), A.S.
Miroshnichenko (3), J. Guarro Flo (4), F. Campos (5), P. Prendergast
(6), S. Danford (3), J.N. Gonzalez-Perez (7), A. Hempelmann (7), M.
Mittag (7), J.H.M.M. Schmitt (7), K.-P. Schroeder (8), S.V. Zharikov
(9)
1 - Liege University, Belgium; 2 - NOAO, Tucson,
AZ, USA; 3 - University of North Carolina, Greensboro, NC, USA; 4
Piera, Spain; 5 - Observatori Puig d’Agulles, Vallirana, Spain; 6 -
Kernersville Observatory, NC, USA; 7 - Hamburger Sternwarte, Germany;
8 - Universidad de Guanajuato, Mexico; 9 - UNAM, Ensenada, Mexico
A growing number of Be and Oe stars, named the gamma Cas stars, are
known for their unusually hard and intense X-ray emission. This
emission could either trace accretion by a compact companion or
magnetic interaction between the star and its decretion disk. To test
these scenarios, we carried out a detailed optical monitoring of
HD45314, the hottest member of the class of gamma Cas stars, along
with dedicated X-ray observations on specific dates. High-resolution
optical spectra were taken to monitor the emission lines formed in
the disk, while X-ray spectroscopy was obtained at epochs when the
optical spectrum of the Oe star was displaying peculiar properties.
Over the last four years, HD45314 has entered a phase of spectacular
variations. The optical emission lines have undergone important
morphology and intensity changes including transitions between
single- and multiple-peaked emission lines as well as shell events,
and phases of (partial) disk dissipation. Photometric variations are
found to be anti-correlated with the equivalent width of the H-alpha
emission. Whilst the star preserved its hard and bright X-ray
emission during the shell phase, the X-ray spectrum during the phase
of (partial) disk dissipation was significantly softer and weaker.
The observed behaviour of HD45314 suggests a direct association
between the level of X-ray emission and the amount of material
simultaneously present in the Oe disk as expected in the magnetic
star-disk interaction scenario.
Reference: A&A
in press
Status: Manuscript has been accepted
Weblink:
https://arxiv.org/abs/1802.05512
Comments:
Email: rauw@astro.ulg.ac.be
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E. Mossoux (1), L. Mahy (2,1) and G. Rauw (1)
1
- Liege University, Belgium; 2 - KU Leuven, Belgium
Context.
HD 54662 is an O-type binary star belonging to the CMa OB1
association. Because of its long-period orbit, this system is an
interesting target to test the adiabatic wind shock model.
Aims. The
goal of this study is to improve our knowledge of the orbital and
stellar parameters of HD 54662 and to analyze its X-ray emission to
test the theoretical scaling of X-ray emission with orbital
separation for adiabatic wind shocks.
Methods. We applied a spectral
disentangling code to a set of optical spectra to determine the
radial velocities and the individual spectra of the primary and
secondary stars. The orbital solution of the system was established
and the reconstructed individual spectra were analyzed by means of
the CMFGEN model atmosphere code. We fitted two X-ray spectra using a
Markov Chain Monte Carlo algorithm and compared these spectra to the
emission expected from adiabatic shocks.
Results. We determine an
orbital period of 2103.4 days, a surprisingly low orbital
eccentricity of 0.11, and a mass ratio m2/m1 of 0.84. Combined with
the orbital inclination inferred in a previous astrometric study, we
obtain surprisingly low masses of 9.7 and 8.2 Msun. From the
disentangled primary and secondary spectra, we infer O6.5 spectral
types for both stars, of which the primary is about two times
brighter than the secondary. The softness of the X-ray spectra for
the two observations, the very small variation of best-fitting
spectral parameters, and the comparison of the X-ray-to-bolometric
luminosity ratio with the canonical value for O-type stars allow us
to conclude that X-ray emission from the wind interaction region is
quite low and that the observed emission is rather dominated by the
intrinsic emission from the stars. We cannot confirm the runaway
status previously attributed to HD 54662 by computing the peculiar
radial and tangential velocities. We find no X-ray emission
associated with the bow shock detected in the infrared.
Conclusions.
The lack of hard X-ray emission from the wind-shock region suggests
that the mass-loss rates are lower than expected and/or that the
pre-shock wind velocities are much lower than the terminal wind
velocities. The bow shock associated with HD 54662 possibly
corresponds to a wind-blown arc created by the interaction of the
stellar winds with the ionized gas of the CMa OB1 association rather
than by a large differential velocity between the binary and the
surrounding interstellar medium.
Reference: A&A
in press
Status: Manuscript has been accepted
Weblink:
http://arxiv.org/abs/1802.06535
Comments:
Email: emossoux@uliege.be
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L. R. Rimulo,$^{1}$, A. C. Carciofi,$^{1}$, R. G.
Vieira,$^{1}$, Th. Rivinius,$^{2}$, D. M. Faes,$^{1}$, A. L.
Figueiredo,$^{1}$, J. E. Bjorkman,$^{3}$, C. Georgy,$^{4}$, M. R.
Ghoreyshi,$^{1}, I. Soszy{\'n}ski$^{5}$
$^{1}$Instituto
de Astronomia, Geof\'{\i}sica e Ci\^encias Atmosf\'ericas,
Universidade de S\~ao Paulo, \\Rua do Mat\~ao 1226, Cidade
Universit\'aria, 05508-900 S\~ao Paulo, SP, Brazil
$^{2}$ESO, European Organization for Astronomical Research in the Southern Hemisphere, Chile
$^{3}$Ritter Observatory, Department of Physics \& Astronomy, Mail Stop 113, University of Toledo, Toledo, OH 43606, US
$^{4}$Observatoire de Gen\`eve, Chemin des Maillettes 51, Sauverny, CH-1290 Versoix, Switzerland\\
$^{5}$Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warsaw, Poland
Be stars are main-sequence massive stars
with emission features in their spectrum, which originates in
circumstellar gaseous discs. Even though the viscous decretion disc
(VDD) model can satisfactorily explain most observations, two
important physical ingredients, namely the magnitude of the viscosity
($\alpha$) and the disk mass injection rate, remain poorly
constrained. The light curves of Be stars that undergo events of disc
formation and dissipation offer an opportunity to constrain these
quantities. A pipeline was developed to model these events that uses
a grid of synthetic light curves, computed from coupled hydrodynamic
and radiative transfer calculations. A sample of 54 Be stars from the
OGLE survey of the Small Magellanic Cloud (SMC) was selected for this
study. Because of the way our sample was selected (bright stars with
clear disc events), it likely represents the densest discs in the
SMC. Like their siblings in the Galaxy, the mass of the disc in the
SMC increases with the stellar mass. The typical mass and angular
momentum loss rates associated with the disk events are of the order
of $\sim$$10^{-10}\, M_\odot\,\mathrm{yr^{-1}}$ and $\sim$$5\times
10^{36}\, \mathrm{g\, cm^{2}\, s^{-2}}$, respectively. The values of
$\alpha$ found in this work are typically of a few tenths, consistent
with recent results in the literature and with the ones found in
dwarf novae, but larger than current theory predicts. Considering the
sample as a whole, the viscosity parameter is roughly two times
larger at build-up ($\left\langle\alpha_\mathrm{bu}\right\rangle =
0.63$) than at dissipation
($\left\langle\alpha_\mathrm{d}\right\rangle = 0.26$). Further work
is necessary to verify whether this trend is real or a result of some
of the model assumptions.
Reference: Accepted
for publication in MRNAS.
Status: Manuscript has been
accepted
Weblink:
http://arxiv.org/abs/1802.07641
Comments:
Email: carciofi@usp.br
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Hugo M. Tabernero (1), Ricardo Dorda (1), Ignacio
Negueruela (1), Carlos González-Fernández (1,2)
(1)
Departamento de Física, Ingeniería de Sistemas y Teoría de la
Señal, Universidad de Alicante, Carretera de San Vicente del Raspeig, E-03690 Alicante, Spain
(2) Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, United Kingdom
We present a self-consistent study of cool
supergiants (CSGs) belonging to the magellanic clouds. We calculated
stellar atmospheric parameters using LTE KURUCZ and MARCS atmospheric
models for more than 400 individual targets by fitting a careful
selection of weak metallic lines. We explore the existence of a T eff
scale and its implications in two different metallicity environments
(each Magellanic cloud). Critical and in-depth tests have been
performed to assess the reliability of our stellar parameters (i.e.
internal error budget, NLTE systematics). In addition, several
Montercarlo tests have been carried out to infer the significance of
the Teff scale found. Our findingspoint towards a unique Teff scale
that seems to be independent of the environment.
Reference:
MNRAS, in
press
Weblink:
https://arxiv.org/abs/1802.03219
Comments:
Email: ricardo.dorda@ua.es
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Prof Dr Jorick S Vink (jsv@arm.ac.uk)
Armagh Observatory and Planetarium
College Hill, Armagh
Northern Ireland
United Kingdom
The Armagh Observatory and Planetarium
invites applications for a Postdoctoral Research Assistant in
Astrophysics. The successful applicant will work with Prof. Dr.
Jorick S. Vink on developing models for the atmospheres and winds of
massive stars. The goal is to compute accurate, dynamically
consistent mass-loss rates that can be employed in stellar evolution
models of massive stars. Situated near the centre of Armagh,
Northern Ireland, the historic Armagh Observatory has active research
groups working in stellar, galactic, solar and solar-system
astronomy. This is a fixed-term position funded by the UK Science and
Technology Facilities Council (STFC). Applicants should have a recent
PhD in Astrophysics with a strong research record in relevant areas,
including substantial experience in the use of major stellar physics
software. The position is available for three years, and can commence
on 1 April 2018 or as soon as possible thereafter.
Starting salary will be in the range GBP 28,323 - 30,929.
Full details of the post are available via our website at
www.armagh.ac.uk. Applicants should submit a CV, statement of
research interests, and the names of three referees, who may be
approached, to: Human Resources, Armagh Observatory, College Hill,
Armagh BT61 9DG, UK (dcn@arm.ac.uk), to arrive no later than 3pm on
Friday 19 of February 2018.
Attention/Comments:
Weblink: www.armagh.ac.uk
Email:
jsv@arm.ac.uk
Deadline:
Feb 19 2018
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Robert Izzard
Astrophysics Research Group
Faculty of Engineering and Physical Sciences
University of Surrey
Guildford,
GU2 7XH
United Kingdom
Applications are invited for a Research Fellow position in the Astrophysics
Research Group of the University of Surrey. The post is funded by the
Science and Technology Facilities Council. The Research Fellow will
undertake research to improve the binary_c framework for stellar
population modelling, development of which is led in Surrey. Binary_c
with be extended to include evolution of very massive single and
binary stars, and algorithms to model ongoing accretion onto very
massive stars. This will then be applied to stellar population
statistics of very massive single and binary stars with applications
to stellar clusters, supernova statistics, close binary evolution and
galactic chemical evolution.
This is a three year fixed-term position to start from April 2018 with salary £30,688 to £34,520 per year.
Further details can be found at https://jobs.surrey.ac.uk/vacancy.aspx?ref=003818
Attention/Comments:
Weblink:
Email:
r.izzard@surrey.ac.uk
Deadline:
Wednesday 14 February
2018
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August 20-24 2018
Venue: Vienna,
IAU general assembly
Session on Metallicity,
Massive Stars, and Chemical Evolution
Contributions are welcome to the Symposium on Dwarf Galaxies to be held during the Vienna general assembly of the IAU, and specifically the session on "Metallicity, Massive Stars, and Chemical Evolution".
Our community is becoming increasingly interested in dwarf irregular galaxies as reservoir of very metal-poor massive stars. Unveiling and characterizing massive stars in these environments is a necessary step to understand their physics at the low-Z end. However, our findings can additionally provide unique insight into the latest episodes of star formation of the host galaxies, their initial mass function, chemical composition and feedback processes. There is large room for synergies between the dwarf galaxy community and ours.
This session will bring researchers from both community together, to foster interaction and future collaborations.
Symposium Scientific Rationale:
Dwarf galaxies are key tools for understanding structure formation and galaxy evolution across cosmic time. These low-mass systems allow us to not only gain a detailed understanding of stellar, chemical, and dynamical properties in the nearby universe, they also provide a unique window into the complex physics of the early universe. We are in an era where increasingly powerful observing facilities and simulations are inspiring new studies of the building blocks of structure at all epochs of the universe. This timely Symposium will bring together the broad dwarf galaxy community, with expertise ranging from local dwarf galaxies to massive star formation in low-metallicity environments, from simulations of feedback in a cosmological context to observations of the faint-end of the luminosity function at high redshift.
Symposium Topics will cover:
- Local Group Dwarf Galaxies
- The Interstellar Medium and Star Formation in Dwarfs
- Metallicity, Massive Stars, and Chemical Evolution
- The Dwarf Galaxy - Environment Connection
- Low-Mass Galaxies at High Redshift
- Dwarfs as Cosmological Probes
- The Future in Dwarf Galaxy Research
Weblink:
https://utw10731.utweb.utexas.edu/
Email:
mgg@cab.inta-csic.es
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3-5 September 2018
Venue: Strasbourg's
Observatory (France)
The nature of the massive Be
star with strong and hard X-ray emission, gamma Cassiopae, remains
enigmatic. In the last decades it became clear, that gamma Cas is a
prototype for the whole new class of stars - there may be thousands
of Cas analogues lurking in the Galaxy! ''The gamma-Cas phenomenon in
Be stars" workshop to be held in Strasbourg, 3-5 September 2018
will assemble the experts in magnetism, binary evolution, X-ray &
UV observations, massive star astrophysics, and stellar disks. The
goal of the workshop is to obtain a comprehensive overview of gamma
Cas analogues, review existing theoretical scenarios on the origin
and physics of these objects, and pave new ways to finally resolve
the gamma Cas puzzle. We invite everybody to join this 3 day
intensive workshop and try your luck in cracking one of the
outstanding problems in modern stellar astrophysics.
Registration and abstract submission are open.
Weblink:
https://gammacas-enigma.sciencesconf.org/
Email:
lida@astro.physik.uni-potsdam.de
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