The enigmatic brown dwarf candidate [KG2001] 102 in the Chamaeleon I cloud: Is it a multiple system?

Abstract

We present deep IJHKs and H_2 images of a region in the Chamaeleon I dark cloud containing the very low-mass young object [KG2001]102, in an attempt to search for multiplicity and molecular outflow in the vicinity of this object. No low-velocity shocked structures were detected in our H_2 image. The broad-band and narrow-band images show that [KG2001]102 is composed of four objects within a radius of about 2 arcsec. The brightest component [KG2001]102 A shows near-IR excess emission and its mass is estimated to be in the range 33 to 55 M_Jup, depending on which model is adopted. Red spectra were obtained of the two fainter components B and C. The spectrum of the former suggests a K7V spectral type while the spectrum of component C is too noisy to allow a reliable classification but rules out a late M-type. The three faint components (B, C and D) have IJHK colors that suggest a much later spectral type, with extinctions similar to other members of the cloud. The computed probability of randomly finding a pair of field stars like [KG2001]102 AB is 1.5 × 10-3 while for a triple optical system like [KG2001]102 ABC, it would be 3.8 × 10-5 and more than an order of magnitude lower for finding a quadruple system like this by chance projection.