We have monitored the ultra-soft X-ray transient 4U 1630-47 in the hard X-ray band using the BATSE instrument on the Compton Gamma Ray Observatory. In a detailed analysis of the first year of data (May 1991 to April 1992), we have identified a possible ~3.5σ detection of a transient event in the light curve from TJD 8380-8410 (May 1991). In images made with the new BATSE occultation imaging technique, this event shows up as an excess consistent with the position of 4U 1630-47 to within the technique's angular resolution (~1°). Lacking independent data, and since the event does not concur with the observed 600 day period of the source, we cannot be certain that the outburst is associated with 4U 1630-47. In addition, we investigate those times during the BATSE data that the ephemeris for 4U 1630-47 does predict activity. Parmar et al. (1995) report the detection of 4U 1630-47 by ROSAT during an observation in September 1992. The source was not detected by BATSE and we derive a 2σ upper limit during September 1992 of ~2.2x10^-2^photons/cm^2^/s, or about 70mCrab, for 5-day integrations. 600-days later in April 1994, we do find evidence of weak emission from 4U 1630-47 at a level of ~15mCrab, owing to a fortuitous lack of interfering sources and good viewing geometry. We compare these results with previous X-ray observations of the source.
Astronomy and Astrophysics Supplement Series
- Pub Date:
- November 1996
- STARS: INDIVIDUAL: 4U 1630-47;
- X-RAYS: STARS