Volume 433, Number 2, April II 2005
|Page(s)||L9 - L12|
|Published online||22 March 2005|
Letter to the Editor
INTEGRAL discovery of persistent hard X-ray emission from the Soft Gamma-ray Repeater SGR 1806–20 *
Istituto di Astrofisica Spaziale e Fisica Cosmica – Sezione di Milano “G. Occhialini” – INAF, via Bassini 15, 20133 Milano, Italy e-mail: firstname.lastname@example.org
2 European Southern Observatory, Alonso de Cordova 3107, Santiago, Chile
3 University of California at Berkeley, Space Sciences Laboratory, Berkeley, CA 94720-7450, USA
Accepted: 27 December 2004
We report the discovery of persistent hard X-ray emission extending up to 150 keV from the soft gamma-ray repeater SGR 1806–20 using data obtained with the INTEGRAL satellite in 2003–2004. Previous observations of hard X-rays from objects of this class were limited to short duration bursts and rare transient episodes of strongly enhanced luminosity (“flares”). The emission observed with the IBIS instrument above 20 keV has a power law spectrum with photon index in the range 1.5–1.9 and a flux of 3 milliCrabs, corresponding to a 20–100 keV luminosity of ~1036 erg s-1 (for a distance of 15 kpc). The spectral hardness and the luminosity correlate with the level of source activity as measured from the number of emitted bursts.
Key words: gamma rays: bursts / pulsars: general / stars: individual: SGR 1806–20
© ESO, 2005
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