Five years of SGR 1900+14 observations with BeppoSAX

¹ Università degli Studi di Pavia, Dipartimento di Fisica Nucleare e Teorica and INFN-Pavia, via Bassi 6, 27100 Pavia, Italy e-mail: paoloesp@iasf-milano.inaf.it
² INAF - Istituto di Astrofisica Spaziale e Fisica Cosmica Milano, via Bassini 15, 20133 Milan, Italy
³ INAF - Istituto di Astrofisica Spaziale e Fisica Cosmica Roma, via Fosso del Cavaliere 100, 00133 Rome, Italy
⁴ Dynetics, Inc., 1000 Explorer Boulevard, Huntsville, AL 35806, USA
⁵ National Space Science and Technology Center, 320 Sparkman Drive, Huntsville, AL 35805, USA

Received: 2 May 2006
Accepted: 27 August 2006

Abstract

We present a systematic analysis of all the BeppoSAX data of the soft gamma-ray repeater SGR 1900+14: these observations allowed us to study the long term properties of the source quiescent emission. In the observation carried out before the 1998 giant flare the spectrum in the 0.8–10 keV energy range was harder and there was evidence for a 20–150 keV emission, possibly associated with SGR 1900+14. This possible hard tail, if compared with the recent INTEGRAL detection of SGR 1900+14, has a harder spectrum (power-law photon index ~1.6 versus ~3) and a 20–100 keV flux ~4 times larger. In the last BeppoSAX observation (April 2002), while the source was entering the long quiescent period that lasted until 2006, the 2–10 keV flux was ~25% below the historical level. We also studied in detail the spectral evolution during the 2001 flare afterglow. This was characterized by a softening that can be interpreted in terms of a cooling blackbody-like component.