Open AccessA near‐infrared spectroscopic search for very‐low‐mass cool companions to notable DA white dwarfs
Author(s) -
Dobbie P. D.,
Burleigh M. R.,
Levan A. J.,
Barstow M. A.,
Napiwotzki R.,
Holberg J. B.,
Hubeny I.,
Howell S. B.
Publication year - 2005
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2005.08720.x
Subject(s) - physics , white dwarf , brown dwarf , astrophysics , stellar classification , infrared , accretion (finance) , astronomy , low mass , type (biology) , stars , ecology , biology
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).