Detection of Additional Be+sdO Systems from IUE Spectroscopy

There is growing evidence that some Be stars were spun up through mass transfer in a close binary system, leaving the former mass donor star as a hot, stripped-down object. There are five known cases of Be stars with hot subdwarf (sdO) companions that were discovered through International Ultraviole...

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Bibliographic Details
Published in:The Astrophysical journal 2018-02, Vol.853 (2), p.156
Main Authors: Wang, Luqian, Gies, Douglas R., Peters, Geraldine J.
Format: Article
Language:English
Subjects:
Astrophysics
binaries: spectroscopic
Binary stars
Mass transfer
Radial velocity
Spectra
Spectroscopy
Spectrum analysis
stars: emission-line, Be
stars: evolution
Subdwarf stars
subdwarfs
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Summary:There is growing evidence that some Be stars were spun up through mass transfer in a close binary system, leaving the former mass donor star as a hot, stripped-down object. There are five known cases of Be stars with hot subdwarf (sdO) companions that were discovered through International Ultraviolet Explorer (IUE) spectroscopy. Here we expand the search for Be+sdO candidates using archival FUV spectra from IUE. We collected IUE spectra for 264 stars and formed cross-correlation functions with a model spectrum for a hot subdwarf. Twelve new candidate Be+sdO systems were found, and eight of these display radial velocity variations associated with orbital motion. The new plus known Be+sdO systems have Be stars with spectral subtypes of B0-B3, and the lack of later-type systems is surprising given the large number of cooler B-stars in our sample. We discuss explanations for the observed number and spectral type distribution of the Be+sdO systems, and we argue that there are probably many Be systems with stripped companions that are too faint for detection through our analysis.
ISSN:0004-637X
1538-4357
DOI:10.3847/1538-4357/aaa4b8