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20 April 2024 |
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Article overview
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New binaries among UV-selected, hot subdwarf stars and population properties | | A. Kawka
; S. Vennes
; S. O'Toole
; P. Nemeth
; D. Burton
; E. Kotze
; D.A.H. Buckley
; | | Date: |
13 Apr 2015 | | Abstract: | We have measured the orbital parameters of seven close binaries, including
six new objects, in a radial velocity survey of 38 objects comprising a hot
subdwarf star with orbital periods ranging from ~0.17 to 3 d. One new system,
GALEX J2205-3141, shows reflection on a M dwarf companion. Three other objects
show significant short-period variations, but their orbital parameters could
not be constrained. Two systems comprising a hot subdwarf paired with a bright
main-sequence/giant companion display short-period photometric variations
possibly due to irradiation or stellar activity and are also short-period
candidates. All except two candidates were drawn from a selection of
subluminous stars in the Galaxy Evolution Explorer ultraviolet sky survey. Our
new identifications also include a low-mass subdwarf B star and likely
progenitor of a low mass white dwarf (GALEX J0805-1058) paired with an unseen,
possibly substellar, companion. The mass functions of the newly identified
binaries imply minimum secondary masses ranging from 0.03 to 0.39 M_solar.
Photometric time series suggest that, apart from GALEX J0805-1058 and
J2205-3141, the companions are most likely white dwarfs. We update the binary
population statistics: Close to 40 per cent of hot subdwarfs have a companion.
Also, we found that the secondary mass distribution shows a low-mass peak
attributed to late-type dwarfs, and a higher-mass peak and tail distribution
attributed to white dwarfs and a few spectroscopic composites. Also, we found
that the population kinematics imply an old age and include a few likely halo
population members. | | Source: | arXiv, 1504.3241 | | Services: | Forum | Review | PDF | Favorites | |
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