AstroSat Detection of a soft X-ray source in HR6819 (QV Tel)
ATel #14739; R. K. Manchanda (USQ, Australia), T. Katoch (TIFR, Mumbai), H. M. Antia (CEBS/TIFR, Mumbai)
on 25 Jun 2021; 13:09 UT
Credential Certification: Tilak Katoch (tilak@tifr.res.in)
Subjects: X-ray, Binary, Black Hole
Proposed non-accreting stellar mass black hole in binary around the B-star, in the B-Be double star system HR 6819 (Rivinis et al. A&A, 637, L3, 2020) was observed with AstroSat observatory [Singh et al., SPIE 9905E..1E, 2016] on three separate occasions corresponding to MJD 59273, 59310 and 59318 for a combined SXT exposure of ~14250 sec.
An ultrasoft X-ray flux was detected during all three observations in the SXT data. The spectral fits in the 0.3-3 keV band correspond to a black body temperature of 165 eV, 90 eV and 110 eV for a fixed n_H value of 5.0 x 10^20 cm^-2. The flux from source was observed to be 5e-12 ergs/cm^2/s in the energy range 0.3 - 3 keV. The observations correspond to binary phase value of 0.143, 0.06, 0.25 respectively (assuming T_conj = 53177.4). Preliminary analysis of the light curves from the large area X-ray proportional counters shows only a very weak emission at a level of ~2-4 counts/sec in the hard X-ray band of 20-80 keV. PDS analysis of the data do not show any short time variations in the source. Soft X-ray data is consistent with those observed from bright stars however, present observations do not preclude the presence of a dormant BH, which may mimic a very low black body temperature. Hard X-ray spectral features in BH sources arise mainly due to large mass accretion and during quiescence emission and the absence of any jet, the observed flux is very weak. Detail analysis of the data from LAXPC along with other co-aligned instruments is in progress.
