Letter to the Editor
The young, wide and very low mass visual binary Lambda Orionis 167*
Laboratorio de Astrofisica Espacial y Fisica Fundamental, LAEFF-INTA, Madrid, Spain e-mail: firstname.lastname@example.org
2 IPAC, Caltech, Pasadena, USA e-mail: email@example.com
3 Astronomy Department, University of California, Berkeley, USA e-mail: firstname.lastname@example.org
Accepted: 11 April 2007
Aims.We look for wide, faint companions around members of the 5 Myr Lambda Orionis open cluster.
Methods.We used optical, near-infrared, and Spitzer/IRAC photometry.
Results.We report the discovery of a very wide very low mass visual binary, LOri167, formed by a brown dwarf and a planetary-mass candidate located at 5 arcsec, which seems to belong to the cluster. We derive Teff of 2125 and 1750 K. If they are members, comparisons with theoretical models indicate masses of 17 and 8 Mjup, with a projected separation of 2000 AU.
Conclusions.Such a binary system would be difficult to explain in most models, particularly those where substellar objects form in the disks surrounding higher mass stars.
Key words: open clusters and associations: individual: Collinder 69 / stars: low-mass, brown dwarfs / stars: binaries: visual / stars: pre-main sequence
© ESO, 2007