A Spectroscopic Orbit for Regulus
D. R. Gies1,2,
S. Dieterich1,
N. D. Richardson1,
A. R. Riedel1,
B. L. Team1,
H. A. McAlister1,
W. G. Bagnuolo, Jr.1,
E. D. Grundstrom1,2,3,
S. Štefl4,
Th. Rivinius4, and
D. Baade5
1
Center for High Angular Resolution Astronomy,
Department of Physics and Astronomy,
Georgia State University, P. O. Box 4106, Atlanta, GA 30302-4106;
gies@chara.gsu.edu, dieterich@chara.gsu.edu, richardson@chara.gsu.edu,
riedel@chara.gsu.edu, team@chara.gsu.edu, hal@chara.gsu.edu,
bagnuolo@chara.gsu.edu,
erika.grundstrom@vanderbilt.edu
2
Visiting Astronomer, Kitt Peak National Observatory,
National Optical Astronomy Observatory, operated by the Association
of Universities for Research in Astronomy, Inc., under contract with
the National Science Foundation.
3
Current address: Physics and Astronomy Department,
Vanderbilt University, 6301 Stevenson Center, Nashville, TN 37235
4
European Organisation for Astronomical Research
in the Southern Hemisphere, Alonso de Cordova 3107, Vitacura,
Santiago de Chile, Chile; sstefl@eso.org, triviniu@eso.org
5
European Organisation for Astronomical Research
in the Southern Hemisphere, Karl-Schwarzschild-Str. 2,
85748 Garching bei München, Germany; dbaade@eso.org
We present a radial velocity study of the rapidly rotating B-star
Regulus that indicates the star is a single-lined spectroscopic
binary. The orbital period (40.11 d) and probable semimajor axis
(0.35 AU) are large enough that the system is not interacting at
present. However, the mass function suggests that the secondary
has a low mass
(M2 > 0.30 M ),
and we argue that the companion may be a white dwarf. Such a star
would be the remnant of a former mass donor that was the source of the
large spin angular momentum of Regulus itself.
Accepted by ApJL
Preprints from
gies@chara.gsu.edu
or on the web at
http://xxx.lanl.gov/abs/0806.3473
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