ISSN 1783-3426
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Magnetic massive stars as progenitors
of "heavy" stellar-mass black holes
Spectroscopic
evolution of massive stars on the main sequence
B
field in OB stars (BOB): The outstandingly strong magnetic field in
the evolved He-strong star CPD-62 2124
Discovery
of rapidly moving partial x-ray absorbers within Gamma
Cassiopeiae
New ATCA, ALMA and VISIR
observations of the candidate LBV SK-67266 (S61): the nebular mass
from modelling 3D density distributions
A
study of the effect of rotational mixing on massive stars evolution:
surface abundances of Galactic O7-8 giant stars
B
fields in OB stars (BOB): Concluding the FORS2 observing campaign
LBV's and Statistical Inference
Physical characterization of Galactic
O-type stars targeted by the IACOB and OWN surveys
New
runaway O-type stars in the first Gaia Data Release
Stellar Magnetism: Challenges, Connections, and Prospects. 14th Potsdam Thinkshop
Massive Star Newsletter -- short questionnaire
Petit, V. (1), Keszthelyi, Z. (2,3), MacInnis, R. (1),
Cohen, D. H. (4), Townsend, R. H. D. (5), Wade, G. A. (2), Thomas, S.
L. (1), Owocki, S. P. (6), Puls, J. (7), ud-Doula, A. (8)
1-
Department of Physics and Space Sciences, Florida Institute of
Technology;
2- Department of Physics, Royal Military College of
Canada;
3- Department of Physics, Engineering Physics and
Astronomy, Queen's University;
4- Department of Physics and
Astronomy, Swarthmore College;
5- Department of Astronomy,
University of Wisconsin-Madison;
6- Department of Physics and
Astronomy, University of Delaware;
7- LMU Munich,
Universitats-Sternwarte, Scheinerstr;
8- Penn State Worthington
Scranton
The groundbreaking detection of gravitational
waves produced by the inspiralling and coalescence of the black hole
(BH) binary GW150914 confirms the existence of "heavy"
stellar-mass BHs with masses >25 Msun. Initial modelling of the
system by Abbott et al. (2016a) supposes that the formation of black
holes with such large masses from the evolution of single massive
stars is only feasible if the wind mass-loss rates of the progenitors
were greatly reduced relative to the mass-loss rates of massive stars
in the Galaxy, concluding that heavy BHs must form in low-metallicity
(Z < 0.25-0.5 Zsun) environments. However, strong surface magnetic
fields also provide a powerful mechanism for modifying mass loss and
rotation of massive stars, independent of environmental metallicity
(ud-Doula & Owocki 2002; ud-Doula et al. 2008). In this paper we
explore the hypothesis that some heavy BHs, with masses >25 Msun
such as those inferred to compose GW150914, could be the natural
end-point of evolution of magnetic massive stars in a
solar-metallicity environment. Using the MESA code, we developed a
new grid of single, non-rotating, solar metallicity evolutionary
models for initial ZAMS masses from 40-80 Msun that include, for the
first time, the quenching of the mass loss due to a realistic dipolar
surface magnetic field. The new models predict TAMS masses that are
significantly greater than those from equivalent non-magnetic models,
reducing the total mass lost by a strongly magnetized 80 Msun star
during its main sequence evolution by 20 Msun. This corresponds
approximately to the mass loss reduction expected from an environment
with metallicity Z = 1/30 Zsun.
Reference: MNRAS in
press
Status: Manuscript has been accepted
Weblink:
https://arxiv.org/abs/1611.08964
Comments:
Email: vpetit@udel.edu
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F. Martins$^1$, A. Palacios$^1$
1- LUPM,
CNRS & Montpellier University
We provide an
observational view of evolutionary models in the Hertzsprung--Russell
diagram, on the main sequence. For that we computed evolutionary
models with the code STAREVOL for 15 < M/Msun < 100. We
subsequently calculated atmosphere models at specific points along
the evolutionary tracks, using the code CMFGEN. Synthetic spectra
obtained in this way were classified as if they were observational
data. We tested our spectral classification by comparison to observed
spectra of various stars. We also compared our results with empirical
data of a large number of OB stars. We obtain spectroscopic sequences
along evolutionary tracks. In our computations, the earliest O stars
(O2-3.5) appear only above ~50 Msun. For later spectral types, a
similar mass limit exists, but is lower. A luminosity class V does
not correspond to the entire main sequence. This only holds for the
15 Msun track. As mass increases, a larger portion of the main
sequence is spent in luminosity class III. Above 50 Msun, supergiants
appear before the end of core-hydrogen burning. Dwarf stars do not
occur on the zero-age main sequence above 80 Msun. Consequently, the
distribution of luminosity class V in the HR diagram cannot be used
to constrain the size of the convective core. The distribution of
dwarfs and giants in the HR diagram agrees well with the location of
stars analyzed by means of quantitative spectroscopy. For
supergiants, there is a slight discrepancy in the sense that
luminosity class I is observed slightly earlier than our predictions.
This is mainly due to wind densities that affect the luminosity class
diagnostic lines. We predict an upper mass limit for dwarf stars (~60
Msun) that is found consistent with the rarity of O2V stars in the
Galaxy. Stars with WNh spectral type are not predicted by our models.
Stronger winds are required to produce the characteristic emission
lines of these objects.
Reference: accepted in
Astronomy & Astrophysics
Status: Manuscript has been
accepted
Weblink:
https://arxiv.org/abs/1612.03044
Comments:
Email: fabrice.martins@umontpellier.fr
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N. Castro(1,2), L. Fossati(3,2), S. Hubrig(4), S. P.
Järvinen(4), N. Przybilla(5), M.-F. Nieva(5), I. Ilyin(4), T. A.
Carroll(4), M. Schöller(6), N. Langer(2), F. R. N. Schneider(7), S.
Simón-Díaz(8,9), T. Morel(10), K. Butler(11) and the BOB
collaboration.
1.-Department of Astronomy, University
of Michigan, 1085 S. University Avenue, Ann Arbor, MI 48109-1107, USA
2.-Argelander-Institut für Astronomie der Universität Bonn,
Auf dem Hügel 71, 53121, Bonn, Germany
3.-Space Research
Institute, Austrian Academy of Sciences, Schmiedlstrasse 6, A-8042
Graz, Austria
4.-Leibniz-Institut für A strophysik Potsdam
(AIP), An der Sternwarte 16, D-14482 Potsdam, Germany
5.-Institut
für Astro- und Teilchenphysik, Universität Innsbruck, Technikerstr.
25/8, 6020 Innsbruck, Austria
6.-European Southern Observatory,
Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany
7.-Department of Physics, University of Oxford, Denys Wilkinson
Building, Keble Road, Oxford OX1 3RH, United Kingdom
8.-Instituto
de Astrofísica de Canarias, 38200, La Laguna, Tenerife, Spain
9.-Universidad de La Laguna, 38205, La Laguna, Tenerife, Spain
10.-Space sciences, Technologies and Astrophysics Research
(STAR) Institute, Université de Liège, Quartier Agora, Allée du 6
Août 19c, Bât. B5C, B4000-Liège, Belgium
11.-
Universitäts-Sternwarte München, Scheinerstr. 1, 81679 München,
Germany
The origin and evolution of magnetism in OB stars
is far from being well understood. With approximately 70 magnetic OB
stars known, any new object with unusual characteristics may turn out
to be a key piece of the puzzle. We report the detection of an
exceptionally strong magnetic field in the He-strong B2IV star CPD-62
2124. Spectropolarimetric FORS2 and HARPSpol observations were
analysed by two independent teams and procedures, concluding on a
strong longitudinal magnetic field of approximately 5.2 kG. The
quantitative characterisation of the stellar atmosphere yields an
effective temperature of 23650±250 K, a surface gravity of 3.95±0.10
dex and a surface helium fraction of 0.35±0.02 by number. The metal
composition is in agreement with the cosmic abundance standard,
except for Mg, Si and S, which are slightly non-solar. The strong and
broad (∼300 km/s) disc-like emission displayed by the Hα line
suggests a centrifugal magnetosphere supported by the strong magnetic
field. Our results imply that CPD-62 2124 is an early B-type star
hosting one of the strongest magnetic fields discovered to date, and
one of the most evolved He-strong stars known, with a fractional
main-sequence lifetime of approximately 0.6.
Reference:
astro-ph:1612.01537
Status: Manuscript has been
accepted
Weblink:
https://arxiv.org/abs/1612.01537
Comments:
Accepted for publication in A&A
Email:
ncastror@umich.edu
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K. Hamaguchi(1, 2), L. Oskinova(3), C. M. P. Russell(4),
R. Petre(4), T. Enoto(5,6), K. Morihana(7), M. Ishida(8)
1:
CRESST and X-ray Astrophysics Laboratory NASA/GSFC, Greenbelt, MD
20771, USA, Kenji.Hamaguchi@nasa.gov
2: Department of Physics,
University of Maryland, Baltimore County, 1000 Hilltop Circle,
Baltimore, MD 21250, USA
3: Institute of Physics and Astronomy,
University of Potsdam, 14476 Potsdam, Germany
4: X-ray
Astrophysics Laboratory NASA/GSFC, Greenbelt, MD 20771, USA
5:
The Hakubi Center for Advanced Research, Kyoto University, Kyoto
606-8302, Japan
6: Department of Astronomy, Kyoto University,
Kitashirakawa- Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan
7:
Nishi-Harima Astronomical Observatory, Center for Astronomy,
University of Hyogo, 407-2, Nichigaichi, Sayo-cho, Sayo, Hyogo,
670-5313, Japan
8: The Institute of Space and Astronautical
Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai,
Chuo-ku, Sagamihara, 252-5210, Japan
Gamma Cassiopeiae is
an enigmatic Be star with unusually strong hard X-ray emission. The
Suzaku observatory detected six rapid X-ray spectral hardening events
called "softness dips" in a ~100 ksec duration observation
in 2011. All the softness dip events show symmetric softness ratio
variations, and some of them have flat bottoms apparently due to
saturation. The softness dip spectra are best described by either
~40% or ~70% partial covering absorption to kT~12 keV plasma emission
by matter with a neutral hydrogen column density of ~2-8e21 cm-2,
while the spectrum outside of these dips is almost free of
absorption. This result suggests the presence of two distinct X-ray
emitting spots in the gamma Cas system, perhaps on a white dwarf
companion with dipole mass accretion. The partial covering absorbers
may be blobs in the Be stellar wind, the Be disk, or rotating around
the white dwarf companion. Weak correlations of the softness ratios
to the hard X-ray flux suggest the presence of stable plasmas at kT
~0.9 and 5 keV, which may originate from the Be or white dwarf winds.
The formation of a Be star and white dwarf binary system requires
mass transfer between two stars; gamma Cas may have experienced such
activity in the past.
Reference: Hamaguchi et al.
2016, Astrophysical Journal, 832, 140.
Status: Manuscript has
been accepted
Weblink:
Comments:
Email: Kenji.Hamaguchi@nasa.gov
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F. Martins$^1$, S. Simon-Diaz$^2$, R.H. Barba$^3$, R.C.
Gamen$^4$, S. Ekstroem$^5$
1- LUPM, CNRS and
Montpellier University; 2- IAC and La Laguna University; 3- La Serena
University; 4- CONICET-UNLP; 5- Geneva Observatory
Massive
star evolution remains only partly constrained. In particular, the
exact role of rotation has been questioned by puzzling properties of
OB stars in the Magellanic Clouds. Our goal is to study the relation
between surface chemical composition and rotational velocity, and to
test predictions of evolutionary models including rotation. We have
performed a spectroscopic analysis of a sample of fifteen Galactic
O7-8 giant stars. This sample is homogeneous in terms of mass,
metallicity and evolutionary state. It is made of stars with a wide
range of projected rotational velocities. We show that the sample
stars are located on the second half of the main sequence, in a
relatively narrow mass range (25-40 Msun). Almost all stars with
projected rotational velocities above 100 km/s have N/C ratios about
ten times the initial value. Below 100 km/s a wide range of N/C
values is observed. The relation between N/C and surface gravity is
well reproduced by various sets of models. Some evolutionary models
including rotation are also able to consistently explain slowly
rotating, highly enriched stars. This is due to differential rotation
which efficiently transports nucleosynthesis products and allows the
surface to rotate slower than the core. In addition, angular momentum
removal by winds amplifies surface braking on the main sequence.
Comparison of the surface composition of O7-8 giant stars with a
sample of B stars with initial masses about four times smaller reveal
that chemical enrichment scales with initial mass, as expected from
theory. Although evolutionary models that include rotation face
difficulties in explaining the chemical properties of O- and B-type
stars at low metallicity, some of them can consistently account for
the properties of main-sequence Galactic O stars in the mass range
25-40 Msun.
Reference:A&A accepted
Status:
Manuscript has been accepted
Weblink:
https://arxiv.org/abs/1611.05223
Comments:
Email:fabrice.martins@umontpellier.fr
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M. Schoeller (1), S. Hubrig (2), L. Fossati (3,4), T.A. Carroll
(2), M. Briquet (5,2), L.M. Oskinova (6), S. Jarvinen (2), I. Ilyin
(2), N. Castro (7,4), T. Morel (5), N. Langer (4), N. Przybilla (8),
M.F. Nieva (8), A.F. Kholtygin (9), H. Sana (10), A. Herrero (11,12),
R.H. Barba (13), A. de Koter (14), the BOB collaboration
(1)
ESO, Garching, Germany; (2) AIP, Potsdam, Germany; (3) OeAW, Graz,
Austria; (4) Univ. Bonn, Germany; (5) Univ. Liege, Belgium; (6) Univ.
Potsdam, Germany; (7) Univ. Michigan, USA; (8) Univ. Innsbruck,
Austria; (9) Univ. St. Petersburg, Russia; (10) KU Leuven, Belgium;
(11) IAC, La Laguna, Spain; (12) Univ. La Laguna, Spain; (13) Univ.
La Serena, Chile; (14) Univ. Amsterdam, The Netherlands
The
"B fields in OB stars" (BOB) collaboration is based on an
ESO Large Programme, to study the occurrence rate, properties, and
ultimately the origin of magnetic fields in massive stars. In the
framework of this programme, we carried out low-resolution
spectropolarimetric observations of a large sample of massive stars
using FORS2 installed at the ESO VLT 8-m telescope. We determined the
magnetic field values with two completely independent reduction and
analysis pipelines. Our in-depth study of the magnetic field
measurements shows that differences between our two pipelines are
usually well within 3sigma errors. From the 32 observations of 28 OB
stars, we were able to monitor the magnetic fields in CPD-57 3509 and
HD164492C, confirm the magnetic field in HD54879, and detect a
magnetic field in CPD-62 2124. We obtain a magnetic field detection
rate of 6+-3% for the full sample of 69 OB stars observed with FORS2
within the BOB programme. For the pre-selected objects with a v sin i
below 60 km/s, we obtain a magnetic field detection rate of 5+-5%. We
also discuss X-ray properties and multiplicity of the objects in our
FORS2 sample with respect to the magnetic field
detections.
Reference:Accepted for publication in
A&A
Status: Manuscript has been accepted
Weblink:
https://arxiv.org/abs/1611.04502
Comments:
Email:mschoell@eso.org
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C. Agliozzo (1,2), R. Nikutta
(3,4), G. Pignata (2,1), N. M. Phillips (5,6), A. Ingallinera (7), C.
Buemi (7), G. Umana (7), P. Leto (7), A. Noriega-Crespo (8), R.
Paladini (9), F. Bufano (7), F. Cavallaro (7,10)
(1)
MAS; (2) UNAB; (3) NOAO; (4) PUC; (5) ESO (6) JAO; (7) OACT; (8)
STScI; (9) IPAC; (10) CSIRO
We present new observations of
the nebula around the Magellanic candidate Luminous Blue Variable
S61. These comprise high-resolution data acquired with the Australia
Telescope Compact Array (ATCA), the Atacama Large
Millimetre/Submillimetre Array (ALMA), and VISIR at the Very Large
Telescope (VLT). The nebula was detected only in the radio, up to 17
GHz. The 17 GHz ATCA map, with 0.8 arcsec resolution, allowed a
morphological comparison with the H$\alpha$ Hubble Space Telescope
image. The radio nebula resembles a spherical shell, as in the
optical. The spectral index map indicates that the radio emission is
due to free-free transitions in the ionised, optically thin gas, but
there are hints of inhomogeneities. We present our new public code
RHOCUBE to model 3D density distributions, and determine via Bayesian
inference the nebula's geometric parameters. We applied the code to
model the electron density distribution in the S61 nebula. We found
that different distributions fit the data, but all of them converge
to the same ionised mass, ~0.1 $\rm M\odot$, which is an order of
magnitude smaller than previous estimates. We show how the nebula
models can be used to derive the mass-loss history with high-temporal
resolution. The nebula was probably formed through stellar winds,
rather than eruptions. From the ALMA and VISIR non-detections, plus
the derived extinction map, we deduce that the infrared emission
observed by space telescopes must arise from extended, diffuse dust
within the ionised region.
Reference:DOI:
10.1093/mnras/stw2986
Status: Manuscript has been
accepted
Weblink:
https://arxiv.org/abs/1611.05259
Comments:
Email:c.agliozzo@gmail.com
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Kris Davidson(1), Roberta M.
Humphreys(1), and
Kerstin Weis(2)
1. University
of Minnesota, 2. Astronomical Institute, Ruhr-Universitaet Bochum,
Germany
Smith & Tomlinson (2015) asserted that
statistical tests disprove the standard view of LBVs, and proposed a
complex alternative scenario. But Humphreys et al.(2016) showed
that
ST's test samples were mixtures of disparate classes of stars, and
genuine LBVs statistically agree with with the standard view.
Smith(2016) objected at great length to this result. Here we explain
why each of his criticisms is incorrect. We also comment on related
claims made by Smith & Stassun(2016). This topic illustrates the
dangers of uncareful statistical sampling and of unstated
assumptions.
Reference: Submitted
Status:
Manuscript has been submitted
Weblink:
http://adsabs.harvard.edu/abs/2016arXiv160802007D
Comments:
Email: kd@astro.umn.edu
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G. Holgado (1,2), S. Simón-Díaz (1,2), R. H. Barbá
(3)
1 - Instituto de Astrofísica de Canarias, E-38200
La Laguna, Tenerife, Spain.
2 - Departamento de Astrofísica,
Univ. de La Laguna, E-38205 La Laguna, Tenerife, Spain.
3 -
Departamento de Física y Astronomía, Univ. de la Serena, Av. Juan
Cisternas 1200 Norte, La Serena, Chile
We present first
results from the quantitative spectroscopic analysis of ∼270
Galactic O-type stars targeted by the IACOB and OWN surveys (implying
the largest sample of stars of this type analyzed homogeneously). We
also evaluate what is the present situation regarding available
information about distances, as provided by the Hipparcos and Gaia
missions.
Reference: To appear in Highlights on
Spanish Astrophysics IX, Proceedings of the XII Scientific Meeting of
the Spanish Astronomical Society held on July 18-22, 2016, in Bilbao,
Spain
Status: Conference proceedings
Weblink:
https://arxiv.org/abs/1611.02634
Comments:
Email: gholgado@iac.es
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J. Maíz Apellániz, R. H.
Barbá, S. Simón-Díaz, I. Negueruela, E. Trigueros Páez
CAB,
ULS, IAC+ULL, UA, CAB+UCM
We have detected 13 new
runaway-star candidates of spectral type O combining the TGAS
(Tycho-Gaia Astrometric Solution) proper motions from Gaia Data
Release 1 (DR1) and the sample from GOSSS (Galactic O-Star
Spectroscopic Survey). We have also combined TGAS and Hipparcos
proper motions to check that our technique recovers many of the
previously known O-type runaways in the sample.
Reference:
To appear in IAUS 239, the lives and death-throes of massive
stars
Status: Conference proceedings
Weblink:
https://arxiv.org/abs/1612.07923
Comments:
Email: jmaiz@cab.inta-csic.es
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June 12-16, 2017
Telegrafenberg,
Potsdam, Germany
The scientific programme will highlight
the most recent observational and theoretical work in the field
including, but not limited to, the following topics:
- the
origin of stellar magnetic fields
- magnetic field geometry and
evolution in pre-main-sequence stars
- magnetic fields,
rotation, and differential rotation on the main sequence
- the
role of small-scale magnetic fields in stellar atmospheres
-
global dynamos, activity cycles, and the rotation-activity-age
relation in solar-type stars
- magnetic fields in massive stars
and magnetically-confined winds
- magnetic star/planet and
disk/planet interaction
- magnetism in the late stages of
stellar evolution
- future perspectives in theory and
observational facilities
Registration and abstract
submission will be opened on the 5th of January 2017.
Weblink:
https://thinkshop.aip.de/14/
Email:shubrig@aip.de
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Dear colleagues, the Organizing Committe of the Massive Star
Commission and the editors of the Massive Star Newsletter have
prepared a short questionnaire to know your opinion about our
Newsletter and collect your suggestions for improvements. Please,
have a look at it. It is a very short questionnaire and we all can
benefit from your answers. Best regards, Artemio Herrero president,
on behalf of the Massive Star IAU Commission and the Newsletter
editors
Weblink:
https://docs.google.com/forms/d/e/1FAIpQLSfpCu0TV0A4DWQ5h_lP7dpsIG_5ti8e_hcVsltRxTgDt1N8Ow/viewform
Email:ahd@iac.es
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