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A near-infrared spectroscopic search for very-low-mass cool companions to notable DA white dwarfs

By P. D. Dobbie, Matthew R. Burleigh, Andrew J. Levan, Martin A. Barstow, R. Napiwotzki, J. B. Holberg, I. Hubeny and S. B. Howell


We have undertaken a detailed near-infrared spectroscopic analysis of eight notable white dwarfs, predominantly of southern declination. In each case the spectrum failed to reveal compelling evidence for the presence of a spatially unresolved, cool, late-type companion. Therefore, we have placed an approximate limit on the spectral type of a putative companion to each degenerate. From these limits we conclude that if GD659, GD50, GD71 or WD2359−434 possesses an unresolved companion then most probably it is substellar in nature (M < 0.072 M⊙). Furthermore, any spatially unresolved late-type companion to RE J0457−280, RE J0623−374, RE J0723−274 or RE J2214−491 most likely has M < 0.082 M⊙. These Results imply that if weak accretion from a nearby late-type companion is the cause of the unusual photospheric composition observed in a number of these degenerates then the companions are of very low mass, beyond the detection thresholds of this study. Furthermore, these Results do not contradict a previously noted deficit of very-low-mass stellar and brown dwarf companions to main sequence F, G, K and early-M type primaries (a≲ 1000 au)

Topics: stars: abundances, binaries: spectroscopic, stars: abundances binaries: spectroscopic, white dwarfs
Publisher: Oxford University Press (OUP), Royal Astronomical Society
Year: 2005
DOI identifier: 10.1111/j.1365-2966.2005.08720.x
OAI identifier:

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