Cyclotron lines from Her X-1

Abstract

Data obtained during four balloon flight observations of hard X-ray emission from Her X-1 provide strong support for the existence of a spectral line feature at 54 keV to 58 keV, while the existence of a second harmonic is uncomfirmed. Because it is difficult to explain the observed feature by a second continuum spectrum or by atomic or nuclear processes, an interpretation in terms of a cyclotron line seems likely. There are two possibilities. There may be a cyclotron absorption feature at approximately 42 keV, and a possible second one at approximately 80 keV. In particular there may be a rather broad absorption feature between the spectral break (25 keV) and approximately 40 keV.