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Title:
Spectroscopy of Young Planetary Mass Candidates with Disks
Authors:
Jayawardhana, Ray; Ivanov, Valentin D.
Affiliation:
AA(Department of Astronomy and Astrophysics, University of Toronto, Toronto, ON M5S 3H8, Canada; ), AB(European Southern Observatory, Ave. Alonso de Cordova 3107, Vitacura, Santiago 19001, Chile; )
Publication:
The Astrophysical Journal, Volume 647, Issue 2, pp. L167-L170. (ApJL Homepage)
Publication Date:
08/2006
Origin:
UCP
ApJ Keywords:
Accretion, Accretion Disks, Stars: Circumstellar Matter, Stars: Planetary Systems, Stars: Formation, Stars: Low-Mass, Brown Dwarfs
DOI:
10.1086/507522
Bibliographic Code:
2006ApJ...647L.167J

Abstract

It is now well established that many young brown dwarfs exhibit characteristics similar to classical T Tauri stars, including infrared excess from disks and emission lines related to accretion. Whether the same holds true for even lower mass objects, namely, those near and below the Deuterium-burning limit, is an important question. Here we present optical spectra of six isolated planetary mass candidates in Chamaeleon II, Lupus I, and Ophiuchus star-forming regions, recently identified by Allers and collaborators to harbor substantial mid-infrared excesses. Our spectra, from ESO's Very Large Telescope and New Technology Telescope, show that four of the targets have spectral types in the ~M9-L1 range, and three of those also exhibit Hα. Their luminosities are consistent with masses of ~5MJ-15MJ according to models of Baraffe and coworkers, thus placing these four objects among the lowest mass brown dwarfs known to be surrounded by circum-substellar disks. Our findings bolster the idea that free-floating planetary mass objects could have infancies remarkably similar to those of Sun-like stars and suggest the intriguing possibility of planet formation around primaries whose masses are comparable to those of extrasolar giant planets. Another target appears to be a brown dwarf (~M8) with prominent Hα emission, possibly arising from accretion. The sixth candidate is likely a background source, underlining the need for spectroscopic confirmation.
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