| Issue |
A&A
Volume 464, Number 2, March III 2007
|
|
|---|---|---|
| Page(s) | 635 - 640 | |
| Section | Stellar structure and evolution | |
| DOI | https://doi.org/10.1051/0004-6361:20066224 | |
| Published online | 02 January 2007 | |
Accurate masses of low mass stars
GJ 765.2AB (0.83 
0.76 
) *,**
1
Special Astrophysical Observatory, N. Arkhyz, Karachai-Cherkesia 369167, Russia e-mail: balega@sao.ru
2
Laboratoire d'Astrophysique de Grenoble, BP 53X, 38041 Grenoble Cedex, France
3
Observatoire de Genève, 1290 Sauverny, Switzerland
4
Cerro Tololo Inter-American Observatory, Casilla 603, La Serena, Chile
5
Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
Received:
10
August
2006
Accepted:
8
November
2006
Context.Because of the lack of precise masses, the coverage of the main-sequence empirical mass-luminosity relation
for stars in the mass range from 0.6 to 0.9 is incomplete.
The nearby K-type visual and spectroscopic binary GJ 765.2 = MLR 224 is a good candidate for new
reliable points in this significant part of the relation.
Aims.We have found a combined orbital solution for the pair and derived physical properties of the components using interferometric and spectroscopic data.
Methods.The diffraction-limited speckle observations were mostly collected at the 6 m BTA telescope, and the velocities of the components were obtained using the CORAVEL radial velocity scanner on the Swiss 1 m telescope.
Results.In a combined solution, the orbital period is
found to be 11.919 yr. The masses of the GJ 765.2 components are
and 
.
The obtained orbital parallax of the system, 
mas,
is 7 percent lower than the Hipparcos value.
The absolute V magnitudes of the stars, derived from the measured speckle magnitude differences, are:
and 
.
The effective temperatures of the components, 
K and 
K,
follow from the 
and 
color indices.
The star metallicity value, estimated from the 6 m telescope spectrum, is [M/H]
dex.
Conclusions.The presented individual masses have 2.4% and 2.5% relative accuracies.
Therefore, the components of GJ 765.2 rank among a dozen stars with masses accurate to within a few percent
in the mass range 0.6-0.9 .
The existing data on the kinematics of GJ 765.2 and its chromospheric activity
indicate that the binary belongs to the middle age
(
yr) thin disk population of the galaxy.
Key words: stars: binaries: visual / stars: fundamental parameters / stars: late-type
© ESO, 2007
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