Observing Variability of Embedded Protostars: The JCMT Transient Survey

The mass of a star is determined by the amount of material accreted during protostellar assembly. Dense core observations within molecular clouds suggest that protostellar assembly is limited by the cloud’s ability to partition material into localized condensations. This is not the entire story, however, as the core material must still reach the forming star, likely through an accretion disk. Uncovering the, possibly variable, mass assembly of a (proto)star requires temporal measurements of the accretion-dominated bolometric luminosity. The JCMT, run by EAO, is using the SCUBA-2 sub-mm camera to monitor eight star-forming regions with a monthly cadence to search for evidence of accretion variability from embedded protostars. Here I present results on our first year of observing the sub-mm brightness of these sources. I discuss the enhanced reduction procedure that yields flux calibration with 2-3% uncertainty, a comprehensive comparison of these fluxes against SCUBA-2 observations taken roughly three years earlier as part of the Gould Belt Survey, and evidence for the first SCUBA-2 sub-mm identified variable source, a Class 0/I protostar with a sub-mm variability amplitude > 25%. The source a known 2 micron periodic binary and we propose that a companion, embedded in the inner disk, is responsible for producing regular bursts of enhanced accretion through the disk onto the forming protostar.

Doug Johnstone
KIAA-PKU Auditorium
Gregory Herczeg
Thursday, July 6, 2017 - 4:00pm to 5:00pm