ASCA Observations of X-Rays from YSOs
Abstract
We report two remarkable results from YSOs found with the hard X-ray band observations of ASCA (> 2 keV). We observed an extremely large flare on a T Tauri star V773 Tau. The peak luminosity in the 0.7-10 keV band is 1.2x1033 ergs s^{-1} at a distance of 150 pc, which is among the highest luminosities of flares on low mass young stellar objects. The temperature at the flare peak is about 10 keV, which is substantially higher than any other flares found in cool stars. It decreased as the flux decreased, but remained still high at about 6 keV. The absorption column is 3.5x1022 H cm^{-3} at the flare peak, and 3.0x1022 H cm^{-3} at the decay tail. Due to these large absorptions, the flare X-rays are invisible in the soft X-ray band of < 2 keV. Based on these high quality X-ray spectra during a full phase of the flare, we discuss the flare physics. We found hard X-rays from three embedded protostars EL29, WL6 and YLW15 in the rho Oph cloud with either a flare-like or a sinusoidal flux variations. We discuss the hard X-rays from the protostars, particularly, the highly variable phenomena.
- Publication:
-
Memorie della Societa Astronomica Italiana
- Pub Date:
- 1997
- Bibcode:
- 1997MmSAI..68.1039H