Exploring the substellar population in the Hyades open cluster

¹ Dpto. Física Aplicada, Universidad Politécnica de Cartagena, 30202 Cartagena, Murcia, Spain
e-mail antonio.perez@upct.es
² Instituto de Astrofísica de Canarias (IAC), Calle Vía Láctea s/n, 38200 La Laguna, Tenerife, Spain
³ Departamento de Astrofísica, Universidad de La Laguna (ULL), 38206 La Laguna, Tenerife, Spain
⁴ Consejo Superior de Investigaciones Científicas, CSIC, Spain

Received: 19 June 2018
Accepted: 21 October 2018

Abstract

Aims. Our aim is to identify substellar members of the nearby Hyades open star cluster to determine the photometric and spectroscopic properties of brown dwarfs at moderately old ages and extend our knowledge of the substellar mass function of the cluster.

Methods. We cross-matched the 2MASS and WISE public catalogues and measured proper motions to identify low-mass stars and brown dwarf member candidates in an area of a radius of ten degrees around the central region of the Hyades cluster. We employed astrometric and photometric criteria, Gaia data, and a maximum likelihood method developed by our group to estimate distances. We selected 36 objects that are candidate Hyades members, 21 of which have not been reported previously.

Results. We have identified 21 new Hyades member candidates that are placed at the lower end of the main sequence. The photometry of 9 candidates places them in the substellar regime, and 2 are at the L/T transition. We also recovered a number of L dwarfs from earlier surveys. Finally, we calculated the mass function for the low-mass population of the cluster and found that the Hyades cluster might have lost 60%–80% of its substellar members.