Stars and brown dwarfs in the σ Orionis cluster: the Mayrit catalogue

Context: The young σ Orionis cluster is an indispensable basis for understanding the formation and evolution of stars, brown dwarfs, and planetary-mass objects. Our knowledge of its stellar population is, however, incomplete.
Aims: I present the Mayrit catalogue, which comprises most of the stars and high-mass brown dwarfs in the cluster.
Methods: The basis of this work is an optical-near infrared correlation between the 2MASS and DENIS catalogues in a circular area of radius 30 arcmin centred on the OB-type binary σ Ori AB. The analysis is supported by a bibliographic search of confirmed cluster members with features of youth and by additional X-ray, mid-infrared, and astrometric data.
Results: I list 241 σ Orionis stars and brown dwarfs with known features of youth, 97 candidate cluster members (40 are new), and 115 back- and foreground sources in the survey area. The 338 cluster members and member candidates constitute the Mayrit catalogue.
Conclusions: This catalogue is a suitable input for studying the spatial ditribution, multiplicity, properties and frequency of discs, and the complete mass function of σ Orionis.

Tables A.1 to A.7 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/478/667