The multiple young stellar objects of HBC 515: An X-ray and millimeter-wave imaging study in (pre-main sequence) diversity

摘要

We present Chandra X-ray Observatory and Submillimeter Array (SMA) imaging of HBC 515 , a system consisting of multiple young stellar objects (YSOs). The five members of HBC 515 represent a remarkably diverse array of YSOs, ranging from the low-mass Class I/II protostar HBC 515B , through Class II and transition disk objects ( HBC 515D and C, respectively), to the “diskless”, intermediate-mass, pre-main sequence (pre-MS) binary HBC 515A. Our Chandra /ACIS imaging establishes that all five components are X-ray sources, with HBC 515A – a subarcsecond-separation binary that is partially resolved by Chandra – being the dominant X-ray source. We detect an X-ray flare associated with HBC 515B. In the SMA imaging, HBC 515B is detected as a strong 1.3 mm continuum emission source; a second, weaker mm continuum source is coincident with the position of the transition disk object HBC 515C . These results strongly support the protostellar nature of HBC 515B, and firmly establish HBC 515A as a member of the rare class of relatively massive, X-ray luminous weak-lined T Tauri stars that are binaries and have shed their disks at very early stages of pre-MS evolution. The coexistence of two such disparate objects within a single, presumably coeval multiple YSO system highlights the influence of pre-MS star mass, binarity, and X-ray luminosity in regulating the lifetimes of circumstellar, planet-forming disks, and the timescales of star-disk interactions.