A proto brown dwarf candidate in Taurus

¹ LAEX-CAB, depto. Astrofísica (INTA-CSIC), PO Box 78, 28691 Villanueva de la Cañada (Madrid), Spain e-mail: barrado@cab.inta-csic.es
² Spitzer Science Center, California Institute of Technology, Pasadena, CA 91125, USA
³ European Southern Observatory, Alonso de Córdova 3107, Vitacura, Santiago, Chile
⁴ Depto. Física Teórica, Facultad de Ciencias, Universidad Autónoma de Madrid, 28049 Madrid, Spain
⁵ Instituto de Astrofísica de Canarias, Av. Vía Láctea s/n, 38200 La Laguna, Spain
⁶ European Space Agency (ESAC), PO Box 78, 28691 Villanueva de la Cañada (Madrid), Spain
⁷ Academia Sinica, Institute of Astronomy and Astrophysics, PO Box 23-141, Taipei 106, Taiwan
⁸ Department of Earth Sciences, National Taiwan Normal University, 88 Sec.4, Ting Chou Rd., Taipei 116, Taiwan

Received: 4 April 2009
Accepted: 22 September 2009

Abstract

Aims. We search for brown dwarfs at the Class 0/I evolutionary stage, or proto brown dwarfs.

Methods. We present a multi wavelength study, ranging from optical at 0.8 μm to radio wavelengths at 6 cm, of a cool, very faint, and red multiple object, SSTB213 J041757, detected by Spitzer toward the Barnard 213 dark cloud, in Taurus.

Results. The SED of SSTB213 J041757 displays a clear excess at long wavelengths resembling that of a Class I object. The mid-IR source has two possible counterparts, A and B, in the near-IR and optical images, and the 350 μm observations detect clear extended emission, presumably from an envelope around the two sources. The position of A & B in the versus colour-colour diagram is consistent with them being Galactic sources and not extragalactic contaminants. A proper-motion study confirms this result for A, while it is inconclusive for B. The temperature and mass of the two possible central objects, according to COND evolutionary models, range between 1550-1750 K and 3-4 , and 950-1300 K and 1-2 , for A and B, respectively. The integrated SED provides bolometric temperatures and luminosities of 280 K and 0.0034 , assuming that the emission at wavelengths >5 μm is associated with component A, and 150 K and 0.0033 , assuming that the emission at wavelengths >5m is associated with component B, which would imply the SSTB213 J041757 object has a luminosity well below the luminosity of other very low luminosity objects discovered up to date.

Conclusions. With these characteristics, SSTB213 J041757 seems to be a promising, and perhaps double, proto brown dwarf candidate.