Reaching the boundary between stellar kinematic groups and very wide binaries

III. Sixteen new stars and eight new wide systems in the β Pictoris moving group

¹ Departamento de Astrofísica y Ciencias de la Atmósfera, Facultad de Ciencias Físicas, Universidad Complutense de Madrid, 28040 Madrid, Spain
e-mail: fjalonso@ucm.es
² Centro de Astrobiología (CSIC-INTA), ESAC PO box 78, 28691 Villanueva de la Cañada, Madrid, Spain
³ Spanish Virtual Observatory, ESAC PO box 78, 28691 Villanueva de la Cañada, Madrid, Spain

Received: 19 June 2015
Accepted: 8 August 2015

Abstract

Aims. We look for common proper motion companions to stars of the nearby young β Pictoris moving group.

Methods. First, we compiled a list of 185 β Pictoris members and candidate members from 35 representative works. Next, we used the Aladin and STILTS virtual observatory tools and the PPMXL proper motion and Washington Double Star catalogues to look for companion candidates. The resulting potential companions were subjects of a dedicated astro-photometric follow-up using public data from all-sky surveys. After discarding 67 sources by proper motion and 31 by colour-magnitude diagrams, we obtained a final list of 36 common proper motion systems. The binding energy of two of them is perhaps too small to be considered physically bound.

Results. Of the 36 pairs and multiple systems, eight are new, 16 have only one stellar component previously classified as a β Pictoris member, and three have secondaries at or below the hydrogen-burning limit. Sixteen stars are reported here for the first time as moving group members. The unexpected large number of high-order multiple systems, 12 triples and two quadruples among 36 systems, may suggest a biased list of members towards close binaries or an increment of the high-order-multiple fraction for very wide systems.