The Substellar Population in σ Orionis

Zapatero Osorio, M. R.; Barrado y Navascués, D.; Béjar, V. J. S.; Rebolo, R.; Caballero, J. A.; Martín, E. L.; Mundt, R.; Eislöffel, J.
Referencia bibliográfica

Brown Dwarfs, Proceedings of IAU Symposium #211, held 20-24 May 2002 at University of Hawaii, Honolulu, Hawaii. Edited by Eduardo Martín. San Francisco: Astronomical Society of the Pacific, 2003, p. 111

Fecha de publicación:
6
2003
Número de autores
8
Número de autores del IAC
2
Número de citas
3
Número de citas referidas
2
Descripción
The σ Orionis cluster (˜3 Myr, 350 pc) is an ideal site to investigate the early evolution of substellar (brown dwarf and planetary mass) objects. To date, the cluster photometric and spectroscopic sequence of free-floaters is known for a wide mass range from 1M&sun; down to roughly 3MJup. The substellar domain covers spectral types that go from mid-M classes to the recently defined ``methane'' T-types, i.e., surface temperatures between ˜3000 K and 800 K. We derive a rising initial substellar mass function in the mass interval of 150--5MJup (dN/dM ˜ M-α, with α = 0.9 ± 0.4). We also find evidence for a extension of this mass function toward lower masses down to 2--3MJup. This indicates that the population of isolated planetary mass objects with masses below the deuterium burning threshold is rather abundant in the cluster.