Stellar and substellar companions of nearby stars from Gaia DR2 – Binarity from proper motion anomaly of stars within 50 pc. (arXiv:1811.08902v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Kervella_P/0/1/0/all/0/1">Pierre Kervella</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Arenou_F/0/1/0/all/0/1">Frédéric Arenou</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mignard_F/0/1/0/all/0/1">François Mignard</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Thevenin_F/0/1/0/all/0/1">Frédéric Thévenin</a>
The census of stellar and substellar companions of nearby stars is largely
incomplete, in particular towards the low mass brown dwarf and long-period
exoplanets. It is however of fundamental importance for stellar and planetary
formation and evolution mechanisms. We aim at characterizing the presence of
physical companions of stellar and substellar mass orbiting nearby stars.
Orbiting secondary bodies influence the proper motion (PM) of their parent
star. Using the Hipparcos (Hip) and Gaia DR2 (GDR2) catalogs, we determine the
long-term PM of each star. We then search for a proper motion anomaly (PMa)
between the long-term PM and the GDR2 (or Hip) measurements, indicative of the
presence of a secondary object. We present a catalog of the PMa of 6741 nearby
stars located within 50 pc. A fraction of ~40% of these objects presents a PMa
at a level of more than 2{sigma}, and ~30% at more than 3{sigma}. We present
a few illustrations of the PMa analysis. We set upper limits of 0.1 – 0.2 MJup
to potential planets of Proxima between 1 and 10 au and 2.5 MJup on any stable
orbit. We confirm that Proxima is gravitationally bound to alpha Cen. We
recover the masses of the known companions of eps Eri, eps Ind, Ross 614, GJ
229, tau Boo and beta Pic. We also detect a possible long-period planet of a
few jovian masses orbiting tau Ceti. The combination of the GDR2 with Hipparcos
and the very high accuracy of the derived PMa already enables to set valuable
constraints on the binarity of nearby objects. The detection of tangential
velocity anomalies at a level of {sigma}(dVtan) = 1.1 m/s per parsec of
distance is already possible with the GDR2. This opens the possibility to
identify long period orbital companions otherwise inaccessible. The
complementarity of Gaia, radial velocity and transit techniques already appears
as remarkably powerful.
The census of stellar and substellar companions of nearby stars is largely
incomplete, in particular towards the low mass brown dwarf and long-period
exoplanets. It is however of fundamental importance for stellar and planetary
formation and evolution mechanisms. We aim at characterizing the presence of
physical companions of stellar and substellar mass orbiting nearby stars.
Orbiting secondary bodies influence the proper motion (PM) of their parent
star. Using the Hipparcos (Hip) and Gaia DR2 (GDR2) catalogs, we determine the
long-term PM of each star. We then search for a proper motion anomaly (PMa)
between the long-term PM and the GDR2 (or Hip) measurements, indicative of the
presence of a secondary object. We present a catalog of the PMa of 6741 nearby
stars located within 50 pc. A fraction of ~40% of these objects presents a PMa
at a level of more than 2{sigma}, and ~30% at more than 3{sigma}. We present
a few illustrations of the PMa analysis. We set upper limits of 0.1 – 0.2 MJup
to potential planets of Proxima between 1 and 10 au and 2.5 MJup on any stable
orbit. We confirm that Proxima is gravitationally bound to alpha Cen. We
recover the masses of the known companions of eps Eri, eps Ind, Ross 614, GJ
229, tau Boo and beta Pic. We also detect a possible long-period planet of a
few jovian masses orbiting tau Ceti. The combination of the GDR2 with Hipparcos
and the very high accuracy of the derived PMa already enables to set valuable
constraints on the binarity of nearby objects. The detection of tangential
velocity anomalies at a level of {sigma}(dVtan) = 1.1 m/s per parsec of
distance is already possible with the GDR2. This opens the possibility to
identify long period orbital companions otherwise inaccessible. The
complementarity of Gaia, radial velocity and transit techniques already appears
as remarkably powerful.
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