scholarly journals Asteroseismology of massive stars with the MOST satellite

2009 ◽  
Vol 5 (H15) ◽  
pp. 366-366
Author(s):  
Anthony F. J. Moffat ◽  
Keyword(s):  
Massive Stars ◽  
Period Range ◽  
Optical Photometry ◽  
X Ray ◽  
Ob Stars ◽  
Stellar Oscillations ◽  
Rotation Periods ◽  
Minute Period ◽  
Orbital Phase ◽  
First Time

AbstractSince 2003 the MOST (Microvariability and Oscillations of STars) microsatellite has obtained typically a month of non-stop, minute-of-time resolution, high-precision, single-broadband optical photometry for each of a significant number of Galactic OB and WR stars. Numerous p- and g-modes were clearly detected in several OB stars, including discovery of g-modes for the first time in a blue supergiant (Saio et al. 2006). True rotation periods were found for some SPBe pulsators (Cameron et al. 2008). Many O stars are remarkably quiet. Five presumably single WR stars have been observed so far, each interesting in its own way. In particular, the cool WR stars WR123 (WN8) and WR103 (WC9d) both show mostly short-lived, multimode oscillations with most of the Fourier power occurring on a day or longer timescale (Moffat et al. 2008a). WR123 also revealed a fairly stable 10-hour periodicity (Lefèvre et al. 2005). All of these oscillations probably arise in the stellar cores. WR111 (WC5) shows no (coherent) oscillations above the detection limit of 0.05 mmag in the 10-minute period range predicted for strange-mode pulsations at a level of 2 mmag (Moffat et al. 2008b). WR110 (WN5-6 and a stronger-than-average X-ray source) and WR124 (WN8h, i.e. in contrast with the previously observed, hydrogen-free WR123 of otherwise similar subtype), both strongly variable with MOST, are currently being analyzed. The next target just observed (late-June to early Aug 2009) is the 30-day eclipsing binary CV Ser = WR113 (WC8d + O8-9IV). Besides stellar oscillations, we will also search for orbital-phase dependent, stochastic variability in CV Ser as wind clumps in the WR component's dense wind pass in front of the O-star.

scholarly journals Magnetic fields, winds and X-rays of massive stars in the Orion nebula cluster

2010 ◽  
Vol 6 (S272) ◽  
pp. 208-209 ◽  
Author(s):  
Véronique Petit ◽  
Gregg A. Wade ◽  
Evelyne Alecian ◽  
Laurent Drissen ◽  
Thierry Montmerle ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Massive Stars ◽  
Theoretical Models ◽  
Magnetic Star ◽  
X Rays ◽  
Orion Nebula ◽  
X Ray ◽  
Ob Stars ◽  
The Impact ◽  
The Relationship

AbstractIn some massive stars, magnetic fields are thought to confine the outflowing radiatively-driven wind. Although theoretical models and MHD simulations are able to illustrate the dynamics of such a magnetized wind, the impact of this wind-field interaction on the observable properties of a magnetic star - X-ray emission, photometric and spectral variability - is still unclear. The aim of this study is to examine the relationship between magnetism, stellar winds and X-ray emission of OB stars, by providing empirical observations and confronting theory. In conjunction with the COUP survey of the Orion Nebula Cluster, we carried out spectropolarimatric ESPaDOnS observations to determine the magnetic properties of massive OB stars of this cluster.

scholarly journals Asteroseismology of OB stars with hundreds of single snapshot spectra (and a few time-series of selected targets)

2014 ◽  
Vol 9 (S307) ◽  
pp. 194-199 ◽  
Author(s):  
S. Simón-Díaz
Keyword(s):  
Time Series ◽  
Massive Stars ◽  
Ob Stars ◽  
Stellar Oscillations ◽  
Large Samples ◽  
Single Snapshot

AbstractImagine we could do asteroseismology of large samples of OB-type stars by using just one spectrum per target. That would be great! But this is probably a crazy and stupid idea. Or maybe not. Maybe we have the possibility to open a new window to investigate stellar oscillations in massive stars that has been in front of us for many years, but has not attracted very much our attention: the characterization and understanding of the so-called macroturbulent broadening in OB-type stars.

scholarly journals Magnetic fields, winds and X-rays of massive stars in the Orion Nebula Cluster

2008 ◽  
Vol 4 (S259) ◽  
pp. 449-452 ◽  
Author(s):  
Véronique Petit ◽  
G. A. Wade ◽  
L. Drissen ◽  
T. Montmerle ◽  
E. Alecian
Keyword(s):  
Magnetic Fields ◽  
Massive Stars ◽  
Magnetic Confinement ◽  
Stellar Winds ◽  
X Rays ◽  
Orion Nebula ◽  
X Ray ◽  
Ob Stars ◽  
Complex Processes ◽  
The Relationship

AbstractIn massive stars, magnetic fields are thought to confine the outflowing radiatively-driven wind, resulting in X-ray emission that is harder, more variable and more efficient than that produced by instability-generated shocks in non-magnetic winds. Although magnetic confinement of stellar winds has been shown to strongly modify the mass-loss and X-ray characteristics of massive OB stars, we lack a detailed understanding of the complex processes responsible. The aim of this study is to examine the relationship between magnetism, stellar winds and X-ray emission of OB stars. In conjunction with a Chandra survey of the Orion Nebula Cluster, we carried out spectropolarimatric ESPaDOnS observations to determine the magnetic properties of massive OB stars of this cluster.

scholarly journals X-rays from magnetic massive OB stars

2013 ◽  
Vol 9 (S302) ◽  
pp. 330-333
Author(s):  
V. Petit ◽  
D. H. Cohen ◽  
Y. Nazé ◽  
M. Gagné ◽  
R. H. D. Townsend ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Large Scale ◽  
Massive Stars ◽  
Magnetic Activity ◽  
Magnetic Characteristics ◽  
Driving Mechanism ◽  
X Rays ◽  
X Ray ◽  
Ob Stars ◽  
Strong Winds

AbstractThe magnetic activity of solar-type and low-mass stars is a well known source of coronal X-ray emission. At the other end of the main sequence, X-rays emission is instead associated with the powerful, radiatively driven winds of massive stars. Indeed, the intrinsically unstable line-driving mechanism of OB star winds gives rise to shock-heated, soft emission (~0.5 keV) distributed throughout the wind. Recently, the latest generation of spectropolarimetric instrumentation has uncovered a population of massive OB-stars hosting strong, organized magnetic fields. The magnetic characteristics of these stars are similar to the apparently fossil magnetic fields of the chemically peculiar ApBp stars. Magnetic channeling of these OB stars' strong winds leads to the formation of large-scale shock-heated magnetospheres, which can modify UV resonance lines, create complex distributions of cooled Halpha emitting material, and radiate hard (~2-5 keV) X-rays. This presentation summarizes our coordinated observational and modelling efforts to characterize the manifestation of these magnetospheres in the X-ray domain, providing an important contrast between the emission originating in shocks associated with the large-scale fossil fields of massive stars, and the X-rays associated with the activity of complex, dynamo-generated fields in lower-mass stars.

scholarly journals Observations of low mass companions to massive stars

2009 ◽  
Vol 5 (H15) ◽  
pp. 760-760
Author(s):  
H. Zinnecker
Keyword(s):  
Massive Stars ◽  
High Mass ◽  
Multiple Systems ◽  
X Ray ◽  
Ob Stars ◽  
Spectroscopic Monitoring ◽  
Short Period ◽  
Low Mass ◽  
X Ray Binaries

Massive stars are known to be multiple systems, often in tight, short-period OB stars binaries (SB1 and SB2, found by spectroscopic monitoring). However, little is known about low-mass companions to massive stars, such as A, F, and G stars with masses in the range of 1 to 3 solar masses. Yet systems of massive stars with wide low-mass companions (of the order of a few AU) must exist, for these are the progenitors of LMXB and HMXB (low-mass and high-mass X-ray binaries).

scholarly journals Chemical abundances of fast-rotating OB stars

2014 ◽  
Vol 9 (S307) ◽  
pp. 94-95
Author(s):  
Constantin Cazorla ◽  
Thierry Morel ◽  
Yaël Nazé ◽  
Gregor Rauw
Keyword(s):  
Massive Stars ◽  
Evolutionary Models ◽  
Rotating Stars ◽  
Chemical Abundances ◽  
Single Star ◽  
Ob Stars ◽  
Detailed Surface ◽  
Normal Nitrogen ◽  
First Time ◽  
Fast Rotating

AbstractFast rotation in massive stars is predicted to induce mixing in their interior, but a population of fast-rotating stars with normal nitrogen abundances at their surface has recently been revealed (Hunter et al.2009; Brott et al.2011, but see Maeder et al.2014). However, as the binary fraction of these stars is unknown, no definitive statements about the ability of single-star evolutionary models including rotation to reproduce these observations can be made. Our work combines for the first time a detailed surface abundance analysis with a radial-velocity monitoring for a sample of bright, fast-rotating Galactic OB stars to put strong constraints on stellar evolutionary and interior models.

scholarly journals X-rays From Centrifugal Magnetospheres in Massive Stars

2014 ◽  
Vol 9 (S307) ◽  
pp. 449-450 ◽  
Author(s):  
Christopher Bard ◽  
Richard Townsend
Keyword(s):  
Mass Loss ◽  
Loss Rate ◽  
Massive Stars ◽  
Mass Loss Rate ◽  
X Rays ◽  
Stellar Rotation ◽  
Hydrodynamic Simulations ◽  
X Ray ◽  
Ob Stars ◽  
Magnetically Confined

AbstractIn the subset of massive OB stars with strong global magnetic fields, X-rays arise from magnetically confined wind shocks (Babel & Montmerle 1997). However, it is not yet clear what the effect of stellar rotation and mass-loss rate is on these wind shocks and resulting X-rays. Here, we present results from a grid of Arbitrary Rigid-Field Hydrodynamic simulations (ARFHD) of a B-star centrifugal magnetosphere with an eye towards quantifying the effect of stellar rotation and mass-loss rate on the level of X-ray emission. The results are also compared to a generalized XADM model for X-rays in dynamical magnetospheres (ud-Doula et al. 2014).

scholarly journals Looking through the photoionisation wake: Vela X−1 at φorb ≈ 0.75 with Chandra/HETG

2021 ◽  
Vol 648 ◽  
pp. A105
Author(s):  
R. Amato ◽  
V. Grinberg ◽  
N. Hell ◽  
S. Bianchi ◽  
C. Pinto ◽  
...  
Keyword(s):  
Compact Object ◽  
High Resolution Spectroscopy ◽  
Plasma Parameters ◽  
Plasma Properties ◽  
X Ray ◽  
Block Algorithm ◽  
Orbital Phase ◽  
Blind Search ◽  
Multi Phase ◽  
First Time

Context. The supergiant X-ray binary Vela X−1 represents one of the best astrophysical sources to investigate the wind environment of an O/B star irradiated by an accreting neutron star. Previous studies and hydrodynamic simulations of the system have revealed a clumpy environment and the presence of two wakes: an accretion wake surrounding the compact object and a photoionisation wake trailing it along the orbit. Aims. Our goal is to conduct, for the first time, high-resolution spectroscopy on Chandra/HETGS data at the orbital phase φorb ≈ 0.75, when the line of sight is crossing the photoionisation wake. We aim to conduct plasma diagnostics, inferring the structure and the geometry of the wind. Methods. We performed a blind search employing a Bayesian block algorithm to find discrete spectral features and identify them thanks to the most recent laboratory results or through atomic databases. Plasma properties were inferred both with empirical techniques and with photoionisation models within CLOUDY and SPEX. Results. We detect and identify five narrow radiative recombination continua (Mg XI-XII, Ne IX-X, O VIII) and several emission lines from Fe, S, Si, Mg, Ne, Al, and Na, including four He-like triplets (S XV, Si XIII, Mg XI, and Ne IX). Photoionisation models reproduce the overall spectrum well, except for the near-neutral fluorescence lines of Fe, S, and Si. Conclusions. We conclude that the plasma is mainly photoionised, but more than one component is most likely present, which is consistent with a multi-phase plasma scenario, where denser and colder clumps of matter are embedded in the hot, photoionised wind of the companion star. Simulations with the future X-ray satellites Athena and XRISM show that a few hundred seconds of exposure is sufficient to disentangle the lines of the Fe Kα doublet and the He-like Fe XXV, improving, in general, the determination of the plasma parameters.

scholarly journals Overall properties of hot, massive stars in the X-ray domain

2010 ◽  
Vol 6 (S272) ◽  
pp. 622-623
Author(s):  
Yael Nazé
Keyword(s):  
Massive Stars ◽  
Plasma Temperature ◽  
Temperature Variability ◽  
X Ray ◽  
Ob Stars ◽  
Bolometric Luminosity ◽  
Medium Resolution ◽  
Complex Project ◽  
The Relationship

AbstractDespite the absence of large surveys, the recent X-ray observatories provide X-ray data for hundreds of massive stars (294 OB stars detected in the 2XMM catalog, 129 OB stars detected in the Chandra Carina Complex Project). Analyzing medium-resolution spectra led to new results on the relationship between the X-ray luminosity and the bolometric luminosity, as well as on the typical properties (plasma temperature, variability) of these objects.

Diphosphinoazine Rhodium(I) and Iridium(I) Complexes

2006 ◽  
Vol 71 (2) ◽  
pp. 197-206 ◽  
Author(s):  
Martin Pošta ◽  
Jan Čermák ◽  
Pavel Vojtíšek ◽  
Ivana Císařová
Keyword(s):  
Rhodium Complexes ◽  
Iridium Complexes ◽  
X Ray ◽  
First Time

The first rhodium complexes of diphosphinoazines [{RhCl(1,2-η:5,6-η-CH=CHCH2CH2CH=CHCH2CH2)}2 {μ-R2PCH2C(But)=NN=C(But)CH2PR2] (R = Ph, Cy, Pri) were prepared by cleavage of the bridge in chloro(cycloocta-1,5-diene)rhodium(I) dimer, the analogous iridium(I) complexes were also prepared for the first time. The X-ray structures of isostructural rhodium and iridium complexes with bis(dicyclohexylphosphino)pinacoloneazine were determined. Diphosphinoazine ligands in the complexes remained in (Z,Z) configuration bridging two RhCl(C8H12) units.

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