BATSE Search for the ~540 keV Feature in the Crab Spectrum Observed by Granat-SIGMA
Abstract
We report the first simultaneous observations of the γ-ray spectrum of the Crab in the energy range 25-1.7 MeV made by the BATSE and SIGMA experiments. These observations were made on 1992 March 10-11. We report specifically results of a search in the JPL BATSE Earth Occultation database for the transient high-energy feature at ~540 keV reported by Granat-SIGMA during this period. We obtain a null result for this feature on both March 10 and March 11. The time-averaged continuum spectrum in the 25 keV-MeV range for the 2 day average spectrum is consistent with a single power law, with photon index of 2.25+/-0.02. The best-fit line flux for either a narrow (0 keV FWHM) feature at 541 keV or a broad (44 keV FWHM) feature at 536 keV of the same 2 day spectrum is (-1.2+/-0.8)×10-3 and (-1.3+/-0.8)×10-3 photons cm-2 s-1, compared to (4.3+/-1.2)×10-3 and (5.1+/-1.7)×10-3 photons cm-2 s-1, respectively, reported by the SIGMA investigators. The difference of the line fluxes measured simultaneously by the BATSE and SIGMA experiments is estimated to be 3.8 σ significance for the narrow feature and 3.4 σ significance for the broad feature.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- September 2001
- DOI:
- 10.1086/322318
- Bibcode:
- 2001ApJ...559..342W
- Keywords:
-
- Gamma Rays: Observations;
- Stars: Pulsars: Individual: Name: Crab Pulsar