The BP tau disk: A missing link between class II and III objects?

Abstract

We present new single-dish (30-m) observations and an improved analysis of our earlier interferometric observations (Simon et al. 2000) of BP Tau*. Our analysis yields a detailed description of the properties of the circumstellar disk. The disk is small (outer radius 120 AU) and marginally optically thick in the 12COJ = 2→1 line. It is also relatively hot, about 50 K at 100 AU. The mm continuum emission is consistent with a thermal emission from circumstellar dust with an emissivity index β ≃ 0.7, and a disk mass about 1.2 × 10-3 M⊙ for 140 pc). The unusual properties of the circumstellar disk suggest that BP Tau may be a transient object in the process of clearing its disk.