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The Substellar Population in σ Orionis

Published online by Cambridge University Press:  26 May 2016

M. R. Zapatero Osorio ,
D. Barrado y Navascués ,
V. J. S. Béjar ,
R. Rebolo ,
J. A. Caballero ,
E.L. Martín ,
R. Mundt  and
J. Eislöffel
M. R. Zapatero Osorio
Affiliation:
LAEFF-INTA, PO 50727, E-28080 Madrid, Spain
D. Barrado y Navascués
Affiliation:
LAEFF-INTA, PO 50727, E-28080 Madrid, Spain
V. J. S. Béjar
Affiliation:
Instituto de Astrofísica de Canarias, E-38200 La Laguna, Spain
R. Rebolo
Affiliation:
Instituto de Astrofísica de Canarias, E-38200 La Laguna, Spain
J. A. Caballero
Affiliation:
Instituto de Astrofísica de Canarias, E-38200 La Laguna, Spain
E.L. Martín
Affiliation:
Institute of Astronomy, Univ. of Hawaii, Honolulu, HI 96822 USA
R. Mundt
Affiliation:
Max-Planck-Institut für Astronomie, D-69117 Heidelberg, Germany
J. Eislöffel
Affiliation:
Thüringer Landessternwarte Tautenburg, D-07778 Tautenburg, Germany

Abstract

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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 1 M⊙ down to roughly 3 MJup. The substellar domain covers spectral types that go from mid-M classes to the recently defined “methane” T-types, i.e., surface temperatures between ~3000K and 800 K. We derive a rising initial substellar mass function in the mass interval of 150–5 MJup (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 2–3 MJup. This indicates that the population of isolated planetary mass objects with masses below the deuterium burning threshold is rather abundant in the cluster.

Type
Part 2. Observations of Recently Born Substellar Objects
Information
Symposium - International Astronomical Union , Volume 211: Brown Dwarfs , 2003 , pp. 111 - 118
Copyright
Copyright © Astronomical Society of the Pacific 2001 

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