Possible astrometric discovery of a substellar companion to the closest binary brown dwarf system WISE J104915.57–531906.1^⋆,⋆⋆

¹ ESO, Av. Alonso de Cordova 3107, 19001 Casilla, Santiago 19, Chile
e-mail: hboffin@eso.org
² Institut d’Astronomie et d’Astrophysique, Université Libre de Bruxelles (ULB), 1050 Bruxelles, Belgium
³ Departamento de Física y Astronomía, Universidad de Valparaiso, Av. Gran Bretaña 1111, 5030 Playa Ancha, Casilla, Chile
⁴ Las Campanas Observatory, Carnegie Institution of Washington, Colina el Pino, 601 Casilla, La Serena, Chile
⁵ ESO, Karl-Schwarzschild-str. 2, 85478 Garching, Germany

Received: 3 November 2013
Accepted: 4 December 2013

Abstract

Using FORS2 on the Very Large Telescope, we have astrometrically monitored over a period of two months the two components of the brown dwarf system WISE J104915.57-531906.1, the closest one to the Sun. Our astrometric measurements – with a relative precision at the milli-arcsecond scale – allowed us to detect the orbital motion and derive more precisely the parallax of the system, leading to a distance of 2.020 ± 0.019 pc. The relative orbital motion of the two objects is found to be perturbed, which leads us to suspect the presence of a substellar companion around one of the two components. We also performed VRIz photometry of the two components and compared this with models. We confirm the flux reversal of the T dwarf.