X-ray spectra of Orion OB supergiants.
Abstract
The 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.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- August 1983
- DOI:
- 10.1086/161235
- Bibcode:
- 1983ApJ...271..681C
- Keywords:
-
- Orion Constellation;
- Supergiant Stars;
- X Ray Spectra;
- B Stars;
- Early Stars;
- Heao 2;
- O Stars;
- Spaceborne Astronomy;
- Stellar Spectrophotometry;
- Stellar Winds;
- Astrophysics