Optical and infrared photometry of new very low-mass stars and brown dwarfs in the Sigma Orionis cluster

Abstract

We present an RI photometric survey covering an area of 430 arcmin^2 around the multiple star Sigma Orionis. The observations were conducted with the 0.8 m IAC-80 Telescope at the Teide Observatory. The survey limiting R and I magnitudes are 22.5 and 21, and completeness magnitudes 21 and 20, respectively. We have selected 53 candidates from the I vs. R-I colour-magnitude diagram (I=14-20) that follow the previously known photometric sequence of the cluster. Adopting an age of 2-4 Myr for the cluster, we find that these objects span a mass range from 0.35 Msol to 0.015 Msol. We have performed J-band photometry of 52 candidates and Ks photometry for 12 of them, with the result that 50 follow the expected infrared sequence for the cluster, thus confirming with great confidence that the majority of the candidates are bona fide members. JHKs photometry from the Two Micron All Sky Survey (2MASS) is available for 50 of the candidates and are in good agreement with our data. Out of 48 candidates, which have photometric accuracies better than 0.1 mag in all bands, only three appear to show near-infrared excesses.

Acepted to be published in Astronomische Nachrichten. 9 pages, 7 figures

References in corpus (4)

• Lithium and Halpha in stars and brown dwarfs of sigma Orionis
• The Substellar Mass Function in sigma Orionis
• No disks around low-mass stars and brown dwarfs in the young sigma Orionis cluster?
• Proper motion of very low mass stars and brown dwarfs in the Pleiades cluster

Cited by in corpus (10)

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• Precision photometric monitoring of very low mass Sigma Orionis cluster members: variability and rotation at a few Myr
• A survey for low mass spectroscopic binary stars in the young clusters around sigma Orionis and lambda Orionis
• Determining the recurrence timescale of long-lasting YSO outbursts
• Search and characterization of T-type planetary mass candidates in the sigma Orionis cluster
• A Pulsation Search Among Young Brown Dwarfs and Very Low Mass Stars
• A novel survey for young substellar objects with the W-band filter VI: Spectroscopic census of sub-stellar members and the IMF of $\sigma$ Orionis cluster
• Characterization of the known T type dwarfs towards the Sigma Orionis cluster
• Exploration about the origin of galactic and extragalactic star clusters through simulated H-R diagrams