Bibcode
Lodieu, N.; Leggett, S. K.; Bergeron, P.; Nitta, A.
Referencia bibliográfica
The Astrophysical Journal, Volume 692, Issue 2, pp. 1506-1516 (2009).
Fecha de publicación:
2
2009
Revista
Número de citas
7
Número de citas referidas
6
Descripción
We have paired the second data release of the Large Area Survey of the
UKIRT Infrared Deep Sky Survey with the fifth data release of the Sloan
Digital Sky Survey to identify 10 cool white dwarf candidates, from
their photometry and astrometry. Of these 10, one was previously known
to be a very cool white dwarf. We have obtained optical spectroscopy for
seven of the candidates using the GMOS-N spectrograph on Gemini North,
and have confirmed all seven as white dwarfs. Our photometry and
astrometry indicate that the remaining two objects are also white
dwarfs. The model analysis of the photometry and available spectroscopy
shows that the seven confirmed new white dwarfs, and the two new likely
white dwarfs, have effective temperatures in the range of T
eff = 5400-6600 K. Our analysis of the previously known white
dwarf confirms that it is cool, with T eff = 3800 K. The
cooling age for this dwarf is 8.7 Gyr, while that for the nine ~ 6000 K
white dwarfs is 1.8-3.6 Gyr. We are unable to determine the masses of
the white dwarfs from the existing data, and therefore we cannot
constrain the total ages of the white dwarfs. The large cooling age for
the coolest white dwarf in the sample, combined with its low estimated
tangential velocity, suggests that it is an old member of the thin disk,
or a member of the thick disk of the Galaxy, with an age of 10-11 Gyr.
The warmer white dwarfs appear to have velocities typical of the thick
disk or even halo; these may be very old remnants of low-mass stars, or
they may be relatively young thin-disk objects with unusually high space
motion.