X-Ray Spectral Study of Two X-Ray Binaries: 4U 1957+11 and 2S 1543-624
Abstract
The X-ray observations of two binary systems, 4U 1957+11 and 2S 1543-624, by the High Eccentric Lunar Occultation Satellite (EXOSAT) satellite are analyzed. The continuum spectra are best fitted by a superposition of a blackbody spectrum (kT approximately = 1 keV) and emission from a Comptonized region, consistent with the spectra of low-mass X-ray binary systems. The Comptonization parameters found for 4U 1957+11 are observed to change significantly from kTe greater than 12.5 keV and tau less than 4.5 in the higher intensity state to kTe approximately = 1.3 keV and tau approximately = 22 in the lower intensity state. The values of kTe and tau derived for 2S 1543-624 are limited to be greater than 4 keV and less than 4.8, respectively. A broad line ascribed to be due to the flouresence of iron is detected in both the objects with an equivalent width of approximately 60-200 eV. The blackbody radius is approxiamtely 3.3 km for 2S 1543-624 and approximately 4.9 km in the case of 4U 1957+11 in its higher intensity state. In an observation of 4U 1957+11 with approximately 20% lower intensity, the blackbody component was not detected. Some possible interpretations of the results are discussed, and an estimate of approximately 108 is derived for the magnetic field on the surface of the neutron star in 4U 1957+11.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- February 1994
- DOI:
- 10.1086/173687
- Bibcode:
- 1994ApJ...421..753S
- Keywords:
-
- Spaceborne Astronomy;
- Spectrum Analysis;
- Stellar Spectra;
- X Ray Astronomy;
- X Ray Binaries;
- X Ray Spectra;
- Black Body Radiation;
- Compton Effect;
- Data Reduction;
- Exos Satellites;
- Stellar Magnetic Fields;
- Astronomy;
- STARS: BINARIES: CLOSE;
- STARS: INDIVIDUAL ALPHANUMERIC: 2S 1543-624;
- STARS: INDIVIDUAL ALPHANUMERIC: 4U 1957;
- 11;
- X-RAYS: STARS