S Ori J053825.4-024241: a classical T Tauri-like object at the substellar boundary

    Authors

    J. A. Caballero; E. L. Martin; M. R. Z. Osorio; V. J. S. Bejar; R. Rebolo; Y. Pavlenko;R. Wainscoat

    Comments

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    Abbreviated Journal Title

    Astron. Astrophys.

    Keywords

    stars : low mass, brown dwarfs; accretion, accretion discs; stars :; variables : general; Galaxy : open clusters and associations :; individuals : sigma Orionis; LOW-MASS STARS; SIGMA-ORIONIS CLUSTER; YOUNG BROWN DWARFS; O-TYPE STARS; H-ALPHA; EVOLUTIONARY MODELS; EMISSION-LINES; FORBIDDEN-LINE; ACCRETION; SPECTROSCOPY; Astronomy & Astrophysics

    Abstract

    We present a spectrophotometric analysis of S Ori J053825.4-024241, a candidate member close to the substellar boundary of the young (1-8 Myr), nearby (similar to 360 pc) sigma Orionis star cluster. Our optical and near-infrared photometry and low-resolution spectroscopy indicate that S Ori J053825.4-024241 is a likely cluster member with a mass estimated from evolutionary models at 0.06(-0.02)(+0.07) M-circle dot, which makes the object a probable brown dwarf. The radial velocity of S Ori J053825.4-024241 is similar to the cluster systemic velocity. This target, which we have classified as an M 6.0 +/- 1.0 low-gravity object, shows excess emission in the near-infrared and anomalously strong photometric variability for its type ( from the blue to the J band), suggesting the presence of a surrounding disc. The optical spectroscopic observations show a continuum excess at short wavelengths and a persistent and resolved Ha emission (pseudo-equivalent width of similar to-250 angstrom) in addition to the presence of other forbidden and permitted emission lines, which we interpret as indicating accretion from the disc and possibly mass loss. We conclude that despite the low mass of S Ori J053825.4-024241, this object exhibits some of the properties typical of active classical T Tauri stars.

    Journal Title

    Astronomy & Astrophysics

    Volume

    445

    Issue/Number

    1

    Publication Date

    1-1-2006

    Document Type

    Article

    Language

    English

    First Page

    143

    Last Page

    U63

    WOS Identifier

    WOS:000233995600016

    ISSN

    0004-6361

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