Chandra Grating Spectroscopy Of Embedded Wind Shock X-Ray Emission From O Stars Shows Low Plasma Temperatures And Significant Wind Absorption
Monthly Notices Of The Royal Astronomical Society
We present a uniform analysis of six examples of embedded wind shock (EWS) O star X-ray sources observed at high resolution with the Chandra grating spectrometers. By modelling both the hot plasma emission and the continuum absorption of the soft X-rays by the cool, partially ionized bulk of the wind we derive the temperature distribution of the shock-heated plasma and the wind mass-loss rate of each star. We find a similar temperature distribution for each star’s hot wind plasma, consistent with a power-law differential emission measure, dlogEMdlogT, with a slope a little steeper than −2, up to temperatures of only about 107 K. The wind mass-loss rates, which are derived from the broadband X-ray absorption signatures in the spectra, are consistent with those found from other diagnostics. The most notable conclusion of this study is that wind absorption is a very important effect, especially at longer wavelengths. More than 90 per cent of the X-rays between 18 and 25 Å produced by shocks in the wind of ζ Pup are absorbed, for example. It appears that the empirical trend of X-ray hardness with spectral subtype among O stars is primarily an absorption effect.
radiative transfer, stars: early-type, stars: massive, stars: mass-loss, stars: winds, outflows, X-rays: stars
David H. Cohen; V. Vaughn Parts; Graham M. Doskoch , '20; Jiaming Wang , '22; V. Petit; M. A. Leutenegger; and M. Gagné.
"Chandra Grating Spectroscopy Of Embedded Wind Shock X-Ray Emission From O Stars Shows Low Plasma Temperatures And Significant Wind Absorption".
Monthly Notices Of The Royal Astronomical Society.
This work is freely available courtesy of Oxford University Press and the Royal Astronomical Society.