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X-ray spectra of Orion OB supergiantsThe spectra are at a higher energy resolution than earlier X-ray observations of OB supergiants, and this allows stronger constraints to be placed on the location of the emission source in the outer atmosphere. The spectra of all three stars are found to be consistent with thermal sources which are only slightly attenuated by stellar wind opacity and have temperatures of approximately 10 to the (6.5 + or - 0.2) power K. A number of explanations of the soft X-ray flux distributions of early-type stars are tested. A model with the X rays coming only from a corona in a slab at the base of the wind does not seem a possibility unless the ionization or density structure of the overlying material is significantly different from that usually assumed for a cool wind. A model where the X rays are produced by radiatively driven shocks, some of which must be strong, can explain the X-ray luminosity and satisfy upper limits on the absorption by oxygen derived from the data. A high-energy (greater than 1 keV) contribution from a base coronal zone is considered possible. The spectrum of Zeta Ori shows emission near 2 keV, wich can be interpreted as line emission of Si XIII and S XV from a very hot source component with T = 1.5 x 10 to the 7th K.
Document ID
19830061843
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Cassinelli, J. P.
(Washburn Observatory Madison, WI, United States)
Swank, J. H.
(NASA Goddard Space Flight Center Laboratory for High Energy Astrophysics, Greenbelt, MD, United States)
Date Acquired
August 11, 2013
Publication Date
August 15, 1983
Publication Information
Publication: Astrophysical Journal, Part 1
Volume: 271
ISSN: 0004-637X
Subject Category
Astrophysics
Accession Number
83A43061
Funding Number(s)
CONTRACT_GRANT: NAG8-410
Distribution Limits
Public
Copyright
Other

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