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Full-Text Articles in Physical Sciences and Mathematics
Measuring The Shock-Heating Rate In The Winds Of O Stars Using X-Ray Line Spectra, David H. Cohen, Zequn Li , '16, K. G. Gayley, S. P. Owocki, J. O. Sundqvist, V. Petit, M. A. Leutenegger
Measuring The Shock-Heating Rate In The Winds Of O Stars Using X-Ray Line Spectra, David H. Cohen, Zequn Li , '16, K. G. Gayley, S. P. Owocki, J. O. Sundqvist, V. Petit, M. A. Leutenegger
Physics & Astronomy Faculty Works
We present a new method for using measured X-ray emission line fluxes from O stars to determine the shock-heating rate due to instabilities in their radiation-driven winds. The high densities of these winds means that their embedded shocks quickly cool by local radiative emission, while cooling by expansion should be negligible. Ignoring for simplicity any non-radiative mixing or conductive cooling, the method presented here exploits the idea that the cooling post-shock plasma systematically passes through the temperature characteristic of distinct emission lines in the X-ray spectrum. In this way, the observed flux distribution among these X-ray lines can be used …
X-Ray Emission From Magnetic Massive Stars, Y. Nazé, V. Petit, M. Rinbrand, David H. Cohen, S. Owocki, A. Ud-Doula, G. A. Wade
X-Ray Emission From Magnetic Massive Stars, Y. Nazé, V. Petit, M. Rinbrand, David H. Cohen, S. Owocki, A. Ud-Doula, G. A. Wade
Physics & Astronomy Faculty Works
Magnetically confined winds of early-type stars are expected to be sources of bright and hard X-rays. To clarify the systematics of the observed X-ray properties, we have analyzed a large series of Chandra and XMM-Newton observations, corresponding to all available exposures of known massive magnetic stars (over 100 exposures covering ~60% of stars compiled in the catalog of Petit et al.). We show that the X-ray luminosity is strongly correlated with the stellar wind mass-loss rate, with a power-law form that is slightly steeper than linear for the majority of the less luminous, lower-${\dot{M}}$ B stars and flattens for the …
Measuring Mass-Loss Rates And Constraining Shock Physics Using X-Ray Line Profiles Of O Stars From The Chandra Archive, David H. Cohen, Emma E. Wollman , '09, M. A. Leutenegger, J. O. Sundqvist, A. W. Fullerton, J. Zsargó, S. P. Owocki
Measuring Mass-Loss Rates And Constraining Shock Physics Using X-Ray Line Profiles Of O Stars From The Chandra Archive, David H. Cohen, Emma E. Wollman , '09, M. A. Leutenegger, J. O. Sundqvist, A. W. Fullerton, J. Zsargó, S. P. Owocki
Physics & Astronomy Faculty Works
We quantitatively investigate the extent of wind absorption signatures in the X-ray grating spectra of all non-magnetic, effectively single O stars in the Chandra archive via line profile fitting. Under the usual assumption of a spherically symmetric wind with embedded shocks, we confirm previous claims that some objects show little or no wind absorption. However, many other objects do show asymmetric and blueshifted line profiles, indicative of wind absorption. For these stars, we are able to derive wind mass-loss rates from the ensemble of line profiles, and find values lower by an average factor of 3 than those predicted by …