Publications of the MPIfR
Optical & Infrared
Interferometry Group
Balega, Y.Y.; Beuzit, J.-L.; Delfosse,
X.; Forveille, T.; Perrier, C.; Mayor, M.; Ségransan, D.; Udry, S.;
Tokovinin, A. A.; Schertl, D.; Weigelt, G.; Balega, I.I.; Malogolovets,
E. V.
Accurate masses of low mass stars: GJ 765.2
AB(0.83 Mo + 0.76 Mo)
Astronomy and Astrophysics, Volume 464, Issue 2,
pp.635-640
Abstract
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 Mȯ to 0.9
Mȯ 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 MA=0.831± 0.020 Mȯ and MB=0.763± 0.019 Mȯ.
The obtained orbital parallax of the system, π_orb=31.0±0.5 mas, is 7
percent lower than the Hipparcos value. The absolute V magnitudes of
the stars, derived from the measured speckle magnitude differences,
are: MVA=5.99±0.04 and MVB=6.64±0.05. The effective temperatures of the
components, T_effA=5060±130 K and T_effB=4690±160 K, follow from the
V-K and J-K color indices. The star metallicity value, estimated from
the 6 m telescope spectrum, is [M/H]=-0.35±0.15 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 Mȯ. The
existing data on the kinematics of GJ 765.2 and its chromospheric
activity indicate that the binary belongs to the middle age (3-4× 109
yr) thin disk population of the galaxy.
You can get this publication ...