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Long term spectral variability in the soft gamma-ray repeater SGR 1900+14 |
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| Authors: | Andrea Tiengo Paolo Esposito Sandro Mereghetti Lara Sidoli Diego Götz Marco Feroci Roberto Turolla Silvia Zane Gian Luca Israel Luigi Stella Peter Woods |
| Institution: | 1. INAF-IASF Milano, via Bassini 15, I-20133, Milan, Italy 2. Dipartimento di Fisica Nucleare e Teorica, Università di Pavia, and INFN-Pavia, via Bassi 6, I-27100, Pavia, Italy 3. CEA Saclay, DSM/DAPNIA/Service d’Astrophysique, F-91191, Gif-sur-Yvette, France 4. INAF-IASF Roma, via Fosso del Cavaliere 100, I-00133, Roma, Italy 5. Dipartimento di Fisica, Università di Padova, via Marzolo 8, I-35131, Padova, Italy 6. Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking Surrey, RH5 6NT, United Kingdom 7. INAF, Osservatorio Astronomico di Roma, via Frascati 33, I-00040, Monteporzio Catone, Italy 8. Dynetics, Inc., 1000 Explorer Boulevard, Huntsville, AL, 35806, USA |
| Abstract: | We present a systematic analysis of all the BeppoSAX data of SGR1900+14. The observations spanning five years show that the source was brighter than usual on two occasions: ～20 days after the August 1998 giant flare and during the 105?s long X-ray afterglow following the April 2001 intermediate flare. In the latter case, we explore the possibility of describing the observed short term spectral evolution only with a change of the temperature of the blackbody component. In the only BeppoSAX observation performed before the giant flare, the spectrum of the SGR1900+14 persistent emission was significantly harder and detected also above 10 keV with the PDS instrument. In the last BeppoSAX observation (April 2002) the flux was at least a factor 1.2 below the historical level, suggesting that the source was entering a quiescent period. |
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