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Hot Subluminous Stars

Published online by Cambridge University Press:  30 March 2016

Jesse L. Greenstein
Jesse L. Greenstein*
Affiliation:
Hale Observatories, California Institute of Technology, Carnegie Institution of Washington

Extract

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Extensive mass loss is observed for hot subluminous stars, through P Cygni lines in the ultraviolet. This persists in some sub-dwarf 0 stars, but is generally not observed in white dwarfs. The ultraviolet provides determination of effective temperatures. Among nine sdO’s, the maximum temperature reported is definitely below 60, 000 K; an object at 100, 000 K would be distinguishable. The sdO’s show a wide variety of line strengths, notably in N V, C IV and Si TV, as well as He II. One halo sdB is reported as rich in peculiar elements; it shows anomalous N V for its temperature. The comparison of effective temperatures of white dwarfs observed from space and from the ground gives excellent agreement. The hottest white dwarfs are near 60, 000 K, although one (helium-rich) reaches 80, 000 K. Another helium-rich close binary probably has an accretion disk; it is the only white dwarf to show the expanding shell of N V, C IV, Si IV characteristic of some subdwarfs. Two magnetic white dwarfs have been observed; one has strong unidentifiable features and the smallest known radius.

Type
Ultraviolet Astronomy-New Results from Recent Space Experiments
Information
Highlights of Astronomy , Volume 5: Highlights of Astronomy. As presented at the XVIIth General Assembly of the IAU, 1979 , 1980 , pp. 255 - 262
Copyright
Copyright © Cambridge University Press 1980

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