XMM-Newton observations of the Soft Gamma Ray Repeater SGR 1627-41 in a low luminosity state

¹ INAF - Istituto di Astrofisica Spaziale e Fisica Cosmica Milano, via Bassini 15, 20133 Milano, Italy e-mail: sandro@iasf-milano.inaf.it
² Università degli Studi di Milano, Dipartimento di Fisica, via Celoria 16, 20133 Milano, Italy
³ Università di Padova, Dipartimento di Fisica, via Marzolo 8, 35131 Padova, Italy
⁴ Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking Surrey, RH5 6NT, UK
⁵ INAF - Osservatorio Astronomico di Roma, via Frascati 33, 00040 Monteporzio Catone, Roma, Italy
⁶ INAF - Istituto di Astrofisica Spaziale e Fisica Cosmica Roma, via Fosso del Cavaliere 100, 00133 Roma, Italy
⁷ Università degli Studi dell'Insubria, via Valleggio 11, 22100 Como, Italy

Received: 15 September 2005
Accepted: 11 January 2006

Abstract

The sky region containing the soft gamma-ray repeater SGR 1627-41 has been observed three times with XMM-Newton in February and September 2004. SGR 1627-41 has been detected with an absorbed flux of ~ erg cm^-2 s^-1 (2-10 keV). For a distance of 11 kpc, this corresponds to a luminosity of ~ erg s^-1, the smallest ever observed for a Soft Gamma Repeater and possibly related to the long period of inactivity of this source. The observed flux is smaller than that seen with Chandra in 2001-2003, suggesting that the source was still fading and had not yet reached a steady quiescent level. The spectrum is equally well fit by a steep power law (photon index ~3.2) or by a blackbody with temperature  keV. We also report on the INTEGRAL transient IGR J16358-4726 that lies at ~10' from SGR 1627-41. It was detected only in September 2004 with a luminosity of ~ erg s^-1 (for  kpc), while in February 2004 it was at least a factor 10 fainter.