Observations of short-duration X-ray transients by WATCH on GRANAT
Abstract
During 1990-92, the WATCH all-sky X-ray monitor on Granat discovered six short-duration X-ray transients. In this paper we discuss their possible relationship to peculiar stars. Only one of the fast (few hours) X-ray transients (GRS 1100-771) might be tentatively ascribed to a superflare arising from a young stellar object in the Chamaeleon I star-forming cloud. At the distance of ~ 150 pc, Lx = 1.35 x 10(34) erg s(-1) (8-15 keV), or 2.6 x 10(34) erg s(-1) (0.1-2.4 keV) assuming a thermal spectrum with kT ~ 10 keV, a temperature higher than those previously seen in T Tauri stars (Tsuboi et al. 1998). The peak X-ray luminosity is at least 2 times higher than that derived for the protostar IRS 43 (Grosso et al. 1997) which would make -to our knowledge- the strongest flare ever seen in a YSO. However, the possibility of GRS 1100-771 being an isolated neutron star unrelated to the cloud cannot be excluded, given the relatively large error box provided by WATCH. Regarding the longer duration ( ~ 1 day) X-ray transients, none of them seem to be related to known objects. We suggest that the latter are likely to have originated from compact objects in low-mass or high-mass X-ray binaries, similarly to XTE J0421+560.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- July 1999
- DOI:
- 10.48550/arXiv.astro-ph/9905078
- arXiv:
- arXiv:astro-ph/9905078
- Bibcode:
- 1999A&A...347..927C
- Keywords:
-
- STARS: FLARE;
- STARS: PRE-MAIN SEQUENCE;
- ISM: INDIVIDUAL OBJECTS: CHAMAELEON I CLOUD;
- X-RAYS: BURSTS;
- X-RAYS: STARS;
- Astrophysics
- E-Print:
- Accepted for publication in Astronomy and Astrophysics (5 pages, 2 figures)