Effects of coronal regions on the x-ray flux and ionization conditions in the winds of ob supergiants and of stars

Journal Article · Sun Apr 01 04:00:00 EST 1979 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/156956· OSTI ID:5990868

Cassinelli, J P; Olson, G L

The anomalously strong O VI and N V lines in O stars and the C IV lines in B supergiants may be due to Auger ionization by X-rays from a thin coronal zone at the base of the cool stellar winds. We determine the size of a corona that is necessary to produce the overall ionization conditions in zeta Pup as has been deduced by Olson from line profile analysis. In the ionization balance calculations we account for diffuse radiation field in the wind and for the large optical depths in the He II continuum due to radiative and Auger ionization edges of abundant elements. The X-ray flux transmitted through the wind is calculated and compared with upper limits derived for upper limits derived for zeta Pup observations from ANS and Uhuru satellites. It is found that a coronal zone with a temperature of 5x10/sup 6/ K and a volume emission measure of 10/sup 58/ cm/sup -3/ can produce the required ionization in a wind having a temperature of 30,000--35,000 K. The emergent X-ray flux bears little resemblance to the coronal emissivity because of the opacity of the wind. The X-ray flux nearly reaches the upper limits derived from the ANS observations and, at several energy bands, should be detectable by the HEAO B satellite. A simplified analysis of the Auger ionization process is developed and applied to other Of and OB supergiants. We find that the model can explain the presence of C IV and Si IV in supergaints with effective temperatures as low as 12,000 K and can explain the appearance of O VI and N V lines in early type supergiants as late as BO.5 and B2, respectively.

• Research Organization: Washburn Observatory, University of Wisconsin--Madison
• OSTI ID: 5990868
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 229:1; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640102* -- Astrophysics & Cosmology-- Stars & Quasi-Stellar
Radio & X-Ray Sources
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ABUNDANCE
ATMOSPHERES
CHARGED PARTICLES
CHEMICAL COMPOSITION
ELECTROMAGNETIC RADIATION
GIANT STARS
IONIZATION
IONIZING RADIATIONS
IONS
MATHEMATICAL MODELS
RADIATIONS
STAR MODELS
STARS
STELLAR ATMOSPHERES
STELLAR WINDS
SUPERGIANT STARS
ULTRAVIOLET RADIATION
X RADIATION