Evidence for a Photoevaporated Circumbinary Disk in Orion

Abstract

We have found a photoevaporated disk in the Orion Nebula that includes a wide binary. HST ACS observations of the proplyd 124-132 show two pointlike sources separated by 0.15'', or about 60 AU at the distance of Orion. The two sources have nearly identical I and z magnitudes. We analyze the brightest component, source N, comparing the observed magnitudes with those predicted using a 1 Myr Baraffe/NextGen isochrone with different accretion luminosities and extinctions. We find that a low-mass (simeq0.04 M_⊙) brown dwarf ~1 Myr old with mass accretion rate log dot M simeq -10.3, typical for objects of this mass, and about 2 mag of visual extinction provides the best fit to the data. This is the first observation of a circumbinary disk undergoing photoevaporation and, if confirmed by spectroscopic observations, the first direct detection of a wide substellar pair still accreting and enshrouded in its circumbinary disk.

Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. These observations are associated with program 10246.