The Soft Gamma-Ray Spectrum of A0535+26: Detection of an Absorption Feature at 110 keV by OSSE
Abstract
We present soft gamma-ray observations by the Oriented Scintillation Spectrometer Experiment (OSSE) on the Compton Gamma Ray Observatory (GRO) of the transient X-ray binary pulsar A0535+26. The observations were made 1994 February 8{17, immediately prior to the peak of a giant outburst. The phase- averaged spectrum is complex and cannot be described by a single-component model. We find that structure in the spectrum above 100 keV can best be modeled by an absorption feature near 110 keV, which we interpret as the signature of cyclotron resonant scattering. Because of OSSE's 45-keV threshold, we are unable to make a definitive statement on the presence of a 55-keV absorption line; however we can conclude that if this line does exist, it must have a smaller optical depth than the line at 110 keV. A first harmonic (= fundamental) cyclotron resonance at 110 keV corresponds to a magnetic field strength at the surface of the neutron star of ~1 x 10(exp 13) G (~5 x 10(exp 12) G if the first harmonic is at 55 keV).
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 1995
- Accession Number
- ADA461878
Entities
People
- C. H. Starr
- E. Kendziorra
- G. V. Jung
- J. Eric Grove
- James D. Kurfess
- M. Maisack
- Mark S. Strickman
- P. Kretschmar
- R. Staubert
- Robert L. Kinzer
- W. Neil Johnson
Organizations
- United States Naval Research Laboratory