NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
Two new extremely hot pulsating white dwarfsHigh speed photometry of the extremely hot, nearly degenerate stars PG 1707 + 427 and PG 2131 + 066 reveals that they are low-amplitude pulsating variables. Power spectral analysis shows both to be multiperiodic, with dominant periods of 7.5 and 6.4-6.9 minutes, respectively. Together with the known pulsators PG 1159 - 035 and the central star of the planetary nebula Kohoutek 1-16, these objects define a new pulsational instability strip at the hot edge of the H-R diagram. The variations of these objects closely resemble those of the much cooler pulsating ZZ Ceti DA white dwarfs; both groups are probably nonradial g-mode pulsators. Evolutionary contraction of the PG 1159 - 035 variables may lead to period changes that would be detectable in as little as 1 year. The optical and IUE spectra of the PG 1159 - 035 variables are characterized by absorption lines of C IV and other CNO ions, indicating radiative levitation of species heavier than helium. He II is also present in the spectra, but the hydrogen Balmer lines are absent. Effective temperatures near 100,000 K are required, and the He II 4686 A profiles indicate log g greater than 6. These helium-rich pulsators form the hottest known subgroup of the DO white dwarfs.
Document ID
19840050796
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Bond, H. E.
Grauer, A. D.
Green, R. F.
Liebert, J. W.
Date Acquired
August 12, 2013
Publication Date
April 15, 1984
Publication Information
Publication: Astrophysical Journal, Part 1
Volume: 279
ISSN: 0004-637X
Subject Category
Astrophysics
Report/Patent Number
AD-A144474
AFOSR-TR-84-0652
Accession Number
84A33583
Funding Number(s)
CONTRACT_GRANT: NAG5-38
CONTRACT_GRANT: AF-AFOSR-82-0192
CONTRACT_GRANT: NSF AST-80-17054
CONTRACT_GRANT: NSF AST-82-18624
CONTRACT_GRANT: NSF AST-82-11905
Distribution Limits
Public
Copyright
Other

Available Downloads

There are no available downloads for this record.
No Preview Available