X-Ray Sources
Abstract
M. Ricketts and B. A. Cooke, Leicester University, report: "The Ariel 5 sky-survey instrument has been observing flaring x-ray activity from a source in the region of 3U 0042+32. This is the first observation of this source by the ssi, although the source has been scanned for a total of 50 days since Nov. 1974, during which time the mean flux was less than 1.5 Uhuru cts/s. During 1977 Feb. 3-6 the flux was variable up to 25 Uhuru cts/s and during Feb. 14-17 up to 50 Uhuru cts/s. The 90-percent-confidence region is defined by R.A. = 0h42m, Decl. = +33o.5; 0h42m, +32o.6; 0h45m, +31o.5; 0h44m, +32o.2 (equinox 1950.0)." P. J. N. Davison, University College, London, writes that the Mullard Space Science Laboratory's experiment C on board Ariel 5 observed a turn-on of Her X-1 on Feb. 3d15h +/- 1h UT, the phase in the 1.7-day binary cycle being 0.28 +/- 0.02. R. H. Becker, S. H. Pravdo, J. R. Saba and P. J. Serlemitsos, Goddard Space Flight Center, report the discovery of an x-ray binary pulsator, consistent in position and intensity with 3U 1538-52. The source, detected by the cosmic x-ray spectroscopy experiment on OSO 8, has a pulsation period of 528s.96 +/- 0s.10 and a pulsed fraction of 0.5. Zero phase occurred on 1976 Aug. 25.8 +/- 10.1 UT. J. McClintock, F. Li, J. Nugent and S. Rappaport, Massachusetts Institute of Technology, report that the SAS-3 Group has discovered a 272s.2 +/- 0s.4 periodicity in the x-ray intensity of GX304-1 = 3U 1258-61. The source was observed during Feb. 14.8-21.9 UT and was variable with a mean 1-12 keV intensity ~ 0.02 that of the Crab Nebula. A prominent flare in the 1-12 keV intensity was observed to commence on Feb. 17.83328 UT; the duration of the flare was ~ 100s and the peak intensity > 3 times the ambient source intensity. W. H. G. Lewin, J. A. Hoffman and J. Doty, Massachusetts Institute of Technology, report that the SAS-3 Observatory has detected 23 x-ray bursts between Feb. 6 and 11 from within 1o.5 of the direction of the galactic center; this is a twofold increase over what was observed a year ago (IAUC 2918). A unique transient event, from a location at least 2o from the galactic center and having a brightness comparable to that of the Crab, was observed at about Feb. 7d20h01m25s UT. At low energies (1.3-5 keV) the risetime was 1s.5, and the decay took about 30 min; the hard x-rays (8-35 keV) were delayed by about 1.5 min, after which they rose to a maximum in an additional 2 min. The outburst was preceded by a precursor (simultaneously in the range 1.3-35 keV) of comparable brightness; the precursor started 9s before the onset of the main outburst at low energies and lasted only 4s.
- Publication:
-
International Astronomical Union Circular
- Pub Date:
- February 1977
- Bibcode:
- 1977IAUC.3039....1R