演講資訊

摘要：

Most protostars have luminosities that are fainter than expected from steady-state accretion. One solution to this problem may lie in episodic mass accretion wherein protostars undergo prolonged periods of very low accretion punctuated by short bursts of rapid accretion. The timescales and amplitudes of these bursts and subsequent relaxations are almost entirely unconstrained at the protostellar phase. The James Clerk Maxwell Telescope (JCMT) Transient Survey is the first dedicated submillimetre-wavelength program focused on detecting variability events at the earliest stages of star formation. The Transient Survey performs monthly continuum observations of 8 nearby (<500 pc) star-forming regions at 450 and 850 microns. The survey area contains ~1,000 young stellar objects ranging from Class 0 (deeply embedded) protostars to more evolved Class II (disk-type) objects. By employing relative flux calibration techniques, light curves are produced with an unprecedented precision of 2%-3% rms at 850 microns and 4-6% rms at 450 microns. To date, more than a dozen sources have shown signs of accretion variability. Additionally, the data uncovered the first coronal flare discovered at submillimeter wavelengths, an event interpreted as a magnetic reconnection that energized charged particles to emit gyrosynchrotron/synchrotron radiation. The light curve of this most luminous stellar flare on record displayed a decrease in brightness by a factor of two in less than 30 minutes. The JCMT Transient Survey began in December 2015 and will continue through at least January 2020.