Issue |
A&A
Volume 516, June-July 2010
|
|
---|---|---|
Article Number | L7 | |
Number of page(s) | 4 | |
Section | Letters | |
DOI | https://doi.org/10.1051/0004-6361/201014796 | |
Published online | 22 June 2010 |
Letter to the Editor
The double degenerate system NLTT 11748*
1
Astronomický ústav, Akademie věd České republiky, Fričova 298, 251 65 Ondřejov, Czech Republic e-mail: [kawka;vennes]@sunstel.asu.cas.cz
2
Visiting Astronomer, Kitt Peak National Observatory, National Optical Astronomy Observatory, which is operated by the Association of Universities for Research in Astronomy (AURA) under cooperative
agreement with the National Science Foundation
3
Department of Physics & Astronomy, Francis Marion University, Box 100547, Florence, SC 29501, USA e-mail: tvaccaro@fmarion.edu
Received:
15
April
2010
Accepted:
18
May
2010
We show that the extremely low-mass white dwarf NLTT 11748 (0.17 ) is in a close binary with a fainter companion.
We obtained a series of radial velocity measurements of the low-mass white dwarf using the Hα core and determined an orbital
period of 5.64 h. The
velocity semi-amplitude (K = 274.8 km s-1) and orbital period imply that it is a degenerate star, and that the minimum mass
for the companion is 0.75
(assuming a mass of 0.167
for the primary). Our analysis of Balmer line profiles shows
that a 0.75
white dwarf companion does not contribute more than 2% or 5% of the flux (V-band) for helium- or hydrogen-rich
surfaces, respectively. The kinematics of the system suggest that it belongs to the Galactic halo.
Key words: binaries: close / stars: individual: NLTT 11748 / white dwarfs
© ESO, 2010
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.