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25 April 2024 |
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Activity at the Deuterium-Burning Mass Limit in Orion | | M.R. Zapatero Osorio
; V.J.S. Bejar
; E.L. Martin
; D. Barrado y Navascues
; R. Rebolo
; | | Date: |
18 Mar 2002 | | Subject: | astro-ph | | Affiliation: | LAEFF, Caltech), V.J.S. Bejar (IAC), E.L. Martin (IfA), D. Barrado y Navascues (LAEFF), R. Rebolo (IAC | | Abstract: | We report very intense and variable Halpha emission (pseudo-equivalent widths of ~180, 410 A) of S Ori 55, a probable free-floating, M9-type substellar member of the young sigma Orionis open star cluster. After comparison with state-of-the-art evolutionary models, we infer that S Ori 55 is near or below the cluster deuterium-burning mass borderline, which separates brown dwarfs and planetary-mass objects. We find its mass to be 0.008-0.015 Msun for ages between 1 Myr and 8 Myr, with ~0.012 Msun the most likely value at the cluster age of 3 Myr. The largest Halpha intensity reached the saturation level of log L(Halpha)/L(bol) = -3. We discuss several possible scenarios for such a strong emission. We also show that sigma Orionis M and L dwarfs have in general more Halpha emission than their older field spectral counterparts. This could be due to a decline in the strength of the magnetic field with age in brown dwarfs and isolated planetary-mass objects, or to a likely mass accretion from disks in the very young sigma Orionis substellar members. | | Source: | arXiv, astro-ph/0203283 | | Services: | Forum | Review | PDF | Favorites | |
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