W. Wheaton, Massachusetts Institute of Technology, and the HEAO-A4 experimenters there and at the University of California at San Diego report the discovery of a strong absorption feature near 20 keV in the pulsed spectrum of the transient x-ray binary 4U 0115+63 (cf. IAUC 3163, 3171). The observations were made during Jan. 16d13h23m-16d16h01m UT (when the orbital phase relative to periastron of 4U 0115+63 was 0.35 +/- 0.01). Referred to the pulsed spectrum, the absorption feature has an equivalent width of ~ 2 keV. It is possible that the feature is due to cyclotron absorption. A cyclotron emission line was reported earlier for Her X-l by Trumper et al. (1978, Astrophys. J. 219, L105); see also IAUC 3184.
International Astronomical Union Circular
- Pub Date:
- June 1978