Hercules X-1 hard X-ray pulsations observed from HEAO 1.
Abstract
The 1.24-sec pulsations of Her X-1 in the energy range 13-75 keV have been analyzed in data obtained from the UCSD/MIT experiment on HEAO 1 during observations of the source on three dates in February 1978 and three in August 1978. Observational results are (1) the main pulse broadens somewhat with increasing energy; (2) the pulsation light curve undergoes pronounced changes at the leading edge of the main pulse from day to day; (3) spectral hardening within the main pulse is confirmed; (4) a 40-60 keV spectral feature in the spectrum is confirmed; (5) this feature is resolved, the pulse width broadening is greater than 20%, and its centroid varies with pulsation phase; and (6) the 13-75 keV spectrum does not noticeably vary from day to day, except for an overall intensity factor. Some implications of these results for the prevailing models of Her X-1 and the HZ Her-Her X-1 system are briefly discussed.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- September 1980
- DOI:
- 10.1086/183338
- Bibcode:
- 1980ApJ...240L.127G
- Keywords:
-
- Binary Stars;
- Heao 1;
- Light Curve;
- Stellar Spectra;
- Variable Stars;
- X Ray Sources;
- Earth Magnetosphere;
- Energy Spectra;
- Neutron Stars;
- Pulse Duration;
- Spectral Line Width;
- Spectrum Analysis;
- Astrophysics;
- Pulsations:X-Ray Binaries;
- Spectra:X-Ray Binaries;
- X-Ray Binaries:Models