Millimeter Continuum Image of the Circumstellar Disk around the Young Star Haro 6-5B

Abstract

Aperture synthesis observations of dust continuum emission at 2 mm from the class I object Haro 6-5B, made with the Nobeyama Millimeter Array, are presented. A disklike structure that coincides with the dark lane in the visible and near-infrared images is clearly resolved with a small synthesized beam of 1.33"×1.21" with its position angle (P.A.) of 134°. The beam-deconvolved size of the disk is 2.33"×0.97" at P.A.=138^deg, and the total flux density is 36.7+/-2.6 mJy. The radius and inclination angle of the disk derived from the image are 309+/-18 AU and 67^deg+/-5^deg, respectively. By model fitting of the spectral energy distribution of Haro 6-5B with these values, the power-law index of the dust opacity, β, is derived to be 1.05+/-0.04 and the disk mass is calculated to be 0.021+/-0.002 M_solar. No extended emission with 1000 AU scale is detected, suggesting that the envelope around Haro 6-5B has been almost dissipated and that the object is a transient source from the protostar stage to the T Tauri stage. Based on the observations made at the Nobeyama Radio Observatory, which is a branch of the National Astronomical Observatory, an interuniversity research institute operated by the Ministry of Education, Science, Sports, Culture, and Technology.