scholarly journals Measuring mass-loss rates and constraining shock physics using X-ray line profiles of O stars from the Chandra archive

2014 ◽  
Vol 439 (1) ◽  
pp. 908-923 ◽  
Author(s):  
David H. Cohen ◽  
Emma E. Wollman ◽  
Maurice A. Leutenegger ◽  
Jon O. Sundqvist ◽  
Alex W. Fullerton ◽  
...  
Keyword(s):  
Mass Loss ◽  
Line Profiles ◽  
Shock Physics ◽  
X Ray ◽  
Loss Rates

scholarly journals What Do We Really Know About the Winds of Massive Stars?

2007 ◽  
Vol 3 (S250) ◽  
pp. 89-96
Author(s):  
D. John Hillier
Keyword(s):  
Mass Loss ◽  
Massive Stars ◽  
Standard Theory ◽  
Stellar Winds ◽  
X Rays ◽  
X Ray ◽  
Stellar Photosphere ◽  
Weak Winds ◽  
Ionization Balance ◽  
Loss Rates

AbstractThe standard theory of radiation driven winds has provided a useful framework to understand stellar winds arising from massive stars (O stars, Wolf-Rayet stars, and luminous blue variables). However, with new diagnostics, and advances in spectral modeling, deficiencies in our understanding of stellar winds have been thrust to the forefront of our research efforts. Spectroscopic observations and analyses have shown the importance of inhomogeneities in stellar winds, and revealed that there are fundamental discrepancies between predicted and theoretical mass-loss rates. For late O stars, spectroscopic analyses derive mass-loss rates significantly lower than predicted. For all O stars, observed X-ray fluxes are difficult to reproduce using standard shock theory, while observed X-ray profiles indicate lower mass-loss rates, the potential importance of porosity effects, and an origin surprisingly close to the stellar photosphere. In O stars with weak winds, X-rays play a crucial role in determining the ionization balance, and must be taken into account.

scholarly journals Radiation-hydrodynamical models of X-ray photoevaporation in carbon-depleted circumstellar discs

2019 ◽  
Vol 490 (4) ◽  
pp. 5596-5614 ◽  
Author(s):  
Lisa Wölfer ◽  
Giovanni Picogna ◽  
Barbara Ercolano ◽  
Ewine F van Dishoeck
Keyword(s):  
Mass Loss ◽  
Gas Phase ◽  
Central Star ◽  
X Rays ◽  
Hydrodynamical Models ◽  
X Ray ◽  
Energetic Radiation ◽  
Low Metallicity ◽  
Penetration Depths ◽  
Loss Rates

ABSTRACT The so-called transition discs provide an important tool to probe various mechanisms that might influence the evolution of protoplanetary discs and therefore the formation of planetary systems. One of these mechanisms is photoevaporation due to energetic radiation from the central star, which can in principal explain the occurrence of discs with inner cavities like transition discs. Current models, however, fail to reproduce a subset of the observed transition discs, namely objects with large measured cavities and vigorous accretion. For these objects the presence of (multiple) giant planets is often invoked to explain the observations. In our work, we explore the possibility of X-ray photoevaporation operating in discs with different gas-phase depletion of carbon and show that the influence of photoevaporation can be extended in such low-metallicity discs. As carbon is one of the main contributors to the X-ray opacity, its depletion leads to larger penetration depths of X-rays in the disc and results in higher gas temperatures and stronger photoevaporative winds. We present radiation-hydrodynamical models of discs irradiated by internal X-ray + EUV radiation assuming carbon gas-phase depletions by factors of three, 10, and 100 and derive realistic mass-loss rates and profiles. Our analysis yields robust temperature prescriptions as well as photoevaporative mass-loss rates and profiles which may be able to explain a larger fraction of the observed diversity of transition discs.

scholarly journals Massive star mass-loss revealed by X-ray observations of young supernovae

2018 ◽  
Vol 14 (S346) ◽  
pp. 83-87
Author(s):  
Vikram V. Dwarkadas
Keyword(s):  
Mass Loss ◽  
Massive Stars ◽  
Ambient Medium ◽  
Mass Loss Rate ◽  
Stellar Mass ◽  
X Rays ◽  
X Ray ◽  
The Common ◽  
Almost All ◽  
Loss Rates

AbstractMassive stars lose a considerable amount of mass during their lifetime. When the star explodes as a supernova (SN), the resulting shock wave expands in the medium created by the stellar mass-loss. Thermal X-ray emission from the SN depends on the square of the density of the ambient medium, which in turn depends on the mass-loss rate (and velocity) of the progenitor wind. The emission can therefore be used to probe the stellar mass-loss in the decades or centuries before the star’s death.We have aggregated together data available in the literature, or analysed by us, to compute the X-ray lightcurves of almost all young supernovae detectable in X-rays. We use this database to explore the mass-loss rates of massive stars that collapse to form supernovae. Mass-loss rates are lowest for the common Type IIP supernovae, but increase by several orders of magnitude for the highest luminosity X-ray SNe.

scholarly journals Stellar Winds and Mass-Loss Rates from Be Stars

1982 ◽  
Vol 98 ◽  
pp. 377-385 ◽  
Author(s):  
Theodore P. Snow
Keyword(s):  
Mass Loss ◽  
Stellar Evolution ◽  
Stellar Winds ◽  
Be Stars ◽  
Line Profiles ◽  
Sample Group ◽  
Show Evidence ◽  
Acceleration Zone ◽  
Low Levels ◽  
Loss Rates

Resonance-line profiles of SiIII and SiIV lines in 22 B and Be stars have been analyzed in the derivation of mass-loss rates. Of the 19 known Be or shell stars in the sample group, all but one show evidence of winds. It is argued that for stars of spectral type B1.5 and later, SiIII and SiIV are the dominant stages of ionization, and this conclusion, together with theoretical fits to the line profiles, leads to mass-loss rates between 10-11 and 3 × 10-9 for the stars. The rate of mass loss does not correlate simply with stellar parameters, and probably is variable with time. The narrow FeIII shell lines often seen in the ultraviolet spectra of Be stars may arise at low levels in the wind, below the strong acceleration zone. The mass-loss rates from Be stars are apparently insufficient to affect stellar evolution.

Mass Loss and Stellar Wind in Massive X-Ray Binaries

1980 ◽  
Vol 5 ◽  
pp. 541-547
Author(s):  
H. F. Henrichs
Keyword(s):  
Mass Loss ◽  
Stellar Wind ◽  
Binary Systems ◽  
Massive Stars ◽  
Compact Star ◽  
X Rays ◽  
Early Type ◽  
X Ray ◽  
X Ray Binaries ◽  
Loss Rates

A number of massive stars of early type is found in X-ray binary systems. The catalog of Bradt et al. (1979) contains 21 sources optically identified with massive stars ranging in spectral type from 06 to B5 out of which 13 are (nearly) unevolved stars and 8 are supergiants. Single stars of this type generally show moderate to strong stellar winds. The X-rays in these binaries originate from accretion onto a compact companion (we restrict the discussion to this type of X-rays).We consider the compact star as a probe traveling through the stellar wind. This probe enables us to derive useful information about the mass outflow of massive stars.After presenting the basic data we derive an upper limit to mass loss rates of unevolved early type stars by studying X-ray pulsars. Next we consider theoretical predictions concerning the influence of X-rays on the stellar wind and compare these with the observations. Finally, using new data from IUE, we draw some conclusions about mass loss rates and velocity laws as derived from X-ray binaries.

scholarly journals Is there a Connection Between Non-Synchronous Rotation and X-Ray Emission in Massive Binary Systems?

2004 ◽  
Vol 215 ◽  
pp. 163-165 ◽  
Author(s):  
Sinhué Haro ◽  
Juan Antonio Juárez ◽  
Gloria Koenigsberger
Keyword(s):  
Mass Loss ◽  
Orbital Period ◽  
Binary Systems ◽  
X Ray ◽  
Rotating Systems ◽  
Tidal Forces ◽  
Synchronous Rotation ◽  
Massive Binary Systems ◽  
Loss Rates

A correlation between orbital period and log(LX/Lbol) is found for a sample of B-type binary systems. We suggest that wind-wind collisions are the likely mechanism for generating the X-ray emission, and that the mass-loss rates may be enhanced in non-synchronously rotating systems due to the oscillations that are excited by the tidal forces.

scholarly journals Colliding stellar wind modelling of the X-ray emission from WR 140

2020 ◽  
Vol 500 (4) ◽  
pp. 4837-4848
Author(s):  
Svetozar A Zhekov
Keyword(s):  
Mass Loss ◽  
Effective Mass ◽  
Stellar Wind ◽  
Mass Loss Rate ◽  
Emission Measure ◽  
Strong Line ◽  
Stellar Winds ◽  
Line Profiles ◽  
X Ray ◽  
Binary Orbit

ABSTRACT We modelled the Chandra and Rossi X-ray Timing Explorer X-ray spectra of the massive binary WR 140 in the framework of the standard colliding stellar wind (CSW) picture. Models with partial electron heating at the shock fronts are a better representation of the X-ray data than those with complete temperature equalization. Emission measure of the X-ray plasma in the CSW region exhibits a considerable decrease at orbital phases near periastron. This is equivalent to variable effective mass-loss rates over the binary orbit. At orbital phases near periastron, a considerable X-ray absorption in excess to that from the stellar winds in WR 140 is present. The standard CSW model provides line profiles that in general do not match well the observed line profiles of the strong line features in the X-ray spectrum of WR 140. The variable effective mass-loss rate could be understood qualitatively in CSW picture of clumpy stellar winds where clumps are efficiently dissolved in the CSW region near apastron but not at periastron. However, future development of CSW models with non-spherically symmetric stellar winds might be needed to get a better correspondence between theory and observations.

scholarly journals X-ray spectral diagnostics of activity in massive stars

2010 ◽  
Vol 6 (S272) ◽  
pp. 348-353 ◽  
Author(s):  
David H. Cohen ◽  
Emma E. Wollman ◽  
Maurice A. Leutenegger
Keyword(s):  
Mass Loss ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Broad Band ◽  
Variable Structure ◽  
Spectral Energy ◽  
X Rays ◽  
X Ray ◽  
Spectral Diagnostics ◽  
Loss Rates

AbstractX-rays give direct evidence of instabilities, time-variable structure, and shock heating in the winds of O stars. The observed broad X-ray emission lines provide information about the kinematics of shock-heated wind plasma, enabling us to test wind-shock models. And their shapes provide information about wind absorption, and thus about the wind mass-loss rates. Mass-loss rates determined from X-ray line profiles are not sensitive to density-squared clumping effects, and indicate mass-loss rate reductions of factors of 3 to 6 over traditional diagnostics that suffer from density-squared effects. Broad-band X-ray spectral energy distributions also provide mass-loss rate information via soft X-ray absorption signatures. In some cases, the degree of wind absorption is so high, that the hardening of the X-ray SED can be quite significant. We discuss these results as applied to the early O stars ζ Pup (O4 If), 9 Sgr (O4 V((f))), and HD 93129A (O2 If*).

scholarly journals Wind properties of variable B supergiants

2018 ◽  
Vol 614 ◽  
pp. A91 ◽  
Author(s):  
M. Haucke ◽  
L. S. Cidale ◽  
R. O. J. Venero ◽  
M. Curé ◽  
M. Kraus ◽  
...  
Keyword(s):  
Mass Loss ◽  
Mass Loss Rate ◽  
Empirical Relationship ◽  
Variable Stars ◽  
Stellar Winds ◽  
Radial Pulsation ◽  
Line Profiles ◽  
Stellar Radius ◽  
Wind Variability ◽  
Loss Rates

Context. Variable B supergiants (BSGs) constitute a heterogeneous group of stars with complex photometric and spectroscopic behaviours. They exhibit mass-loss variations and experience different types of oscillation modes, and there is growing evidence that variable stellar winds and photospheric pulsations are closely related. Aims. To discuss the wind properties and variability of evolved B-type stars, we derive new stellar and wind parameters for a sample of 19 Galactic BSGs by fitting theoretical line profiles of H, He, and Si to the observed ones and compare them with previous determinations. Methods. The synthetic line profiles are computed with the non-local thermodynamic equilibrium (NLTE) atmosphere code FASTWIND, with a β-law for hydrodynamics. Results. The mass-loss rate of three stars has been obtained for the first time. The global properties of stellar winds of mid/late B supergiants are well represented by a β-law with β > 2. All stars follow the known empirical wind momentum–luminosity relationships, and the late BSGs show the trend of the mid BSGs. HD 75149 and HD 99953 display significant changes in the shape and intensity of the Hα line (from a pure absorption to a P Cygni profile, and vice versa). These stars have mass-loss variations of almost a factor of 2.8. A comparison among mass-loss rates from the literature reveals discrepancies of a factor of 1 to 7. This large variation is a consequence of the uncertainties in the determination of the stellar radius. Therefore, for a reliable comparison of these values we used the invariant parameter Qr. Based on this parameter, we find an empirical relationship that associates the amplitude of mass-loss variations with photometric/spectroscopic variability on timescales of tens of days. We find that stars located on the cool side of the bi-stability jump show a decrease in the ratio V∞∕Vesc, while their corresponding mass-loss rates are similar to or lower than the values found for stars on the hot side. Particularly, for those variable stars a decrease in V∞∕Vesc is accompanied by a decrease in Ṁ. Conclusions. Our results also suggest that radial pulsation modes with periods longer than 6 days might be responsible for the wind variability in the mid/late-type. These radial modes might be identified with strange modes, which are known to facilitate (enhanced) mass loss. On the other hand, we propose that the wind behaviour of stars on the cool side of the bi-stability jump could fit with predictions of the δ−slow hydrodynamics solution for radiation-driven winds with highly variable ionization.

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