Bibcode
Cortés-Contreras, M.; Béjar, V. J. S.; Caballero, J. A.; Gauza, B.; Montes, D.; Alonso-Floriano, F. J.; Jeffers, S. V.; Morales, J. C.; Reiners, A.; Ribas, I.; Schöfer, P.; Quirrenbach, A.; Amado, P. J.; Mundt, R.; Seifert, W.
Referencia bibliográfica
Astronomy and Astrophysics, Volume 597, id.A47, 13 pp.
Fecha de publicación:
1
2017
Revista
Número de citas
75
Número de citas referidas
67
Descripción
Aims: We search for low-mass companions of M dwarfs and
characterize their multiplicity fraction with the purpose of helping in
the selection of the most appropriate targets for the CARMENES exoplanet
survey. Methods: We obtained high-resolution images in the I band
with the lucky imaging instrument FastCam at the 1.5 m Telescopio Carlos
Sánchez for 490 mid- to late-M dwarfs. For all the detected
binaries, we measured angular separations, position angles, and
magnitude differences in the I band. We also calculated the masses of
each individual component and estimated orbital periods, using the
available magnitude and colour relations for M dwarfs and our own
MJ-spectral type and mass-MI relations. To avoid
biases in our sample selection, we built a volume-limited sample of
M0.0-M5.0 dwarfs that is complete up to 86% within 14 pc.
Results: From the 490 observed stars, we detected 80 companions in 76
systems, of which 30 are new discoveries. Another six companion
candidates require additional astrometry to confirm physical binding.
The multiplicity fraction in our observed sample is 16.7 ± 2.0%.
The bias-corrected multiplicity fraction in our volume-limited sample is
19.5 ± 2.3% for angular separations of 0.2 to 5.0 arcsec
(1.4-65.6 au), with a peak in the distribution of the projected physical
separations at 2.5-7.5 au. For M0.0-M3.5 V primaries, our search is
sensitive to mass ratios higher than 0.3 and there is a higher density
of pairs with mass ratios over 0.8 compared to those at lower mass
ratios. Binaries with projected physical separations shorter than 50 au
also tend to be of equal mass. For 26 of our systems, we estimated
orbital periods shorter than 50 a, 10 of which are presented here for
the first time. We measured variations in angular separation and
position angle that are due to orbital motions in 17 of these systems.
The contribution of binaries and multiples with angular separations
shorter than 0.2 arcsec, longer than 5.0 arcsec, and of spectroscopic
binaries identified from previous searches, although not complete, may
increase the multiplicity fraction of M dwarfs in our volume-limited
sample to at least 36%.
Tables A.1-A.6 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/597/A47
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