Astronomy & Astrophysics

Free access article

Issue		A&A Volume 389, Number 2, July II 2002
Page(s)		494 - 512
Section		Formation, structure and evolution of stars
DOI		10.1051/0004-6361:20020601

A&A 389, 494-512 (2002)
DOI: 10.1051/0004-6361:20020601

Near-infrared spectra of ISO selected Chamaeleon I young stellar objects

M. Gómez¹ and P. Persi²

¹ Observatorio Astronómico de Córdoba, Laprida 854, 5000 Córdoba, Argentina
² Istituto Astrofisica Spaziale e Fisica Cosmica, CNR, Via del Fosso del Cavaliere 100, 00133 Roma, Italia

(Received 15 January 2002 / Accepted 16 April 2002 )

Abstract
We present 0.95-2.5 $\mu$ m moderate ( $R \sim 500$ ) resolution spectra of 19 ISOCAM detected sources in the Chamaeleon I dark cloud. Thirteen of these stars are candidate very low mass members of the cloud proposed by Persi et al. (2000) on basis of the mid-IR color excess. The sample also includes a bona-fide young brown dwarf (Cha H $\alpha$ 1), a transition - stellar/sub-stellar - object one previously known T Tauri star (Sz 33) and three ISOCAM sources with no mid-IR excess. The spectra of the mid-IR color excess sources are relatively flat and featureless in this wavelength range. Both atomic and molecular lines (when in absorption) are partially veiled suggesting the presence of continuum emission from circumstellar dust. In addition some of the sources show Paschen and Brackett lines in emission. We apply the 2 $\mu$ m water vapor index defined by Wilking et al. (1999) to estimate spectral types. These stars have spectral types M0-8. We use Persi et al.'s stellar luminosity determinations, in combination with D'Antona & Mazzitelli latest pre-main sequence evolutionary tracks, to estimate masses and ages. The ISOCAM detected mid-IR excess sources have sub-solar masses down to the H-burning limit and a median age of few $\times$ 10 ⁶ yr, in good agreement with the higher mass members of this cloud.

Key words: techniques: spectroscopic -- stars: formation -- stars: pre-main sequence -- stars: Hertzsprung-Russell (HR) diagram -- stars: low-mass, brown dwarfs -- infrared: stars

Offprint request: M. Gómez, mercedes@oac.uncor.edu

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