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Full-Text Articles in Physical Sciences and Mathematics
Measurements And Analysis Of Helium-Like Triplet Ratios In The X-Ray Spectra Of O-Type Stars, M. A. Leutenegger, F. B.S. Paerels, S. M. Kahn, David H. Cohen
Measurements And Analysis Of Helium-Like Triplet Ratios In The X-Ray Spectra Of O-Type Stars, M. A. Leutenegger, F. B.S. Paerels, S. M. Kahn, David H. Cohen
Physics & Astronomy Faculty Works
We discuss new methods of measuring and interpreting the forbidden-to-intercombination line ratios of heliumlike triplets in the X-ray spectra of O- type stars, including accounting for the spatial distribution of the X-ray-emitting plasma and using the detailed photospheric UV spectrum. Measurements are made for four O stars using archival Chandra HETGS data. We assume an X- ray-emitting plasma spatially distributed in the wind above some minimum radius R-0. We find minimum radii of formation typically in the range of 1.25 < R-0 / R-* < 1.67, which is consistent with results obtained independently from line profile fits. We find no evidence for anomalously low f / i ratios, and we do not require the existence of X-ray-emitting plasmas at radii that are too small to generate sufficiently strong shocks.
The Effect Of Porosity On X-Ray Emission-Line Profiles From Hot-Star Winds, S. P. Owocki, David H. Cohen
The Effect Of Porosity On X-Ray Emission-Line Profiles From Hot-Star Winds, S. P. Owocki, David H. Cohen
Physics & Astronomy Faculty Works
We investigate the degree to which the nearly symmetric form of X- ray emission lines seen in Chandra spectra of early- type supergiant stars could be explained by the possibly porous nature of their spatially structured stellar winds. Such porosity could effectively reduce the bound- free absorption of X- rays emitted by embedded wind shocks, and thus allow a more similar transmission of redshifted and blueshifted emission from the back and front hemispheres, respectively. To obtain the localized self- shielding that is central to this porosity effect, it is necessary that the individual clumps be optically thick. In a medium …
Wind Signatures In The X-Ray Emission-Line Profiles Of The Late-O Supergiant Zeta Orionis, David H. Cohen, M. A. Leutenegger, K. T. Grizzard, Catherine Lois Reed , '05, Roban Hultman Kramer , '03, S. P. Owocki
Wind Signatures In The X-Ray Emission-Line Profiles Of The Late-O Supergiant Zeta Orionis, David H. Cohen, M. A. Leutenegger, K. T. Grizzard, Catherine Lois Reed , '05, Roban Hultman Kramer , '03, S. P. Owocki
Physics & Astronomy Faculty Works
X-ray line-profile analysis has proved to be the most direct diagnostic of the kinematics and spatial distribution of the very hot plasma around O stars. The Doppler-broadened line profiles provide information about the velocity distribution of the hot plasma, while the wavelength-dependent attenuation across a line profile provides information about the absorption to the hot plasma, thus providing a strong constraint on its physical location. In this paper, we apply several analysis techniques to the emission lines in the Chandra High Energy Transmission Grating Spectrometer (HETGS) spectrum of the late-O supergiant zeta Ori (O9.7 Ib), including the fitting of a …