Magnetars as persistent hard X-ray sources: INTEGRAL discovery of a hard tail in SGR 1900+14

Free access article

Issue		A&A Volume 449, Number 2, April II 2006


Page(s)		L31 - L34
Section		Letters
DOI		http://dx.doi.org/10.1051/0004-6361:20064870

A&A 449, L31-L34 (2006)
DOI: 10.1051/0004-6361:20064870

Letter

Magnetars as persistent hard X-ray sources: INTEGRAL discovery of a hard tail in SGR 1900+14

D. Götz¹, S. Mereghetti², A. Tiengo² and P. Esposito^{2, 3}

¹ CEA Saclay, DSM/DAPNIA/Service d'Astrophysique, 91191 Gif-sur-Yvette, France
e-mail: diego.gotz@cea.fr
² INAF - Istituto di Astrofisica Spaziale e Fisica Cosmica, via Bassini 15, 20133 Milano, Italy
³ Dipartimento di Fisica Nucleare e Teorica - Università degli Studi di Pavia, via Bassi 6, 27100 Pavia, Italy

(Received 17 January 2006 / Accepted 20 February 2006)

Abstract
Using 2.5 Ms of data obtained by the INTEGRAL satellite in 2003-2004, we discovered persistent hard X-ray emission from the soft gamma-ray repeater SGR 1900+14. Its 20-100 keV spectrum is well described by a steep power law with photon index $\Gamma=3.1\pm0.5$ and flux $1.5\times10^{-11}$ erg cm^-2 s^-1. Contrary to SGR 1806-20, the only other soft gamma-ray repeater for which persistent emission above 20 keV was reported, SGR 1900+14 has been detected in the hard X-ray range while it was in a quiescent state (the last bursts from this source were observed in 2002). By comparing the broad band spectra (1-100 keV) of all the magnetars detected by INTEGRAL (the two SGRs and three anomalous X-ray pulsars) we find evidence for a different spectral behaviour of these two classes of sources.

Key words: gamma-rays: observations -- pulsars: individual SGR 1900+14 -- pulsars: general

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