Absence of Significant Cool Disks in Young Stellar Objects Exhibiting Repetitive Optical Outbursts

Absence of Significant Cool Disks in Young Stellar Objects Exhibiting Repetitive Optical Outbursts

Authors:

Liu et al

Abstract:

We report Submillimeter Array (SMA) 1.3 mm high angular resolution observations towards the four EXor type outbursting young stellar objects (YSOs) VY Tau, V1118 Ori, V1143 Ori, and NY Ori. The data mostly show low dust masses Mdust in the associated circumstellar disks. Among the sources, NY Ori possesses a relatively massive disk with Mdust∼9×10−4 M⊙. V1118 Ori has a marginal detection equivalent to Mdust∼6×10−5 M⊙. V1143 Ori has a non-detection also equivalent to Mdust less than 6×10−5 M⊙. For the nearest source VY Tau, we get a surprising non-detection which provides a stringent upper limit Mdust less than 6×10−6 M⊙. We interpret our findings as suggesting that the gas and dust reservoirs that feed the short duration, repetitive optical outbursts seen in some EXors may be limited to the small scale, innermost region of their circumstellar disks. This hot dust may have escaped our detection limits. Follow-up, more sensitive millimeter observations are needed to improve our understanding of the triggering mechanisms of EXor type outbursts.