Volume 542, June 2012
|Number of page(s)||4|
|Published online||30 May 2012|
A relativistic iron emission line from the neutron star low-mass X-ray binary GX 3+1
1 INAF-IASF di Palermo, via Ugo La Malfa 153, 90146 Palermo, Italy
2 Institut für Astronomie und Astrophysik, Kepler Center for Astro and Particle Physics, Sand 1, 72076 Tübingen, Germany
3 Department of Physics and Astronomy University of Iowa, Iowa City, IA 52242, USA
4 Dipartimento di Fisica, Università degli Studi di Palermo, via Archirafi, 90100 Palermo, Italy
5 Dipartimento di Fisica, Università degli Studi di Cagliari, SP Monserrato-Sestu, KM 0.7, Monserrato, Italy
Received: 26 March 2012
Accepted: 8 May 2012
We present the results of a spectroscopic study of the Fe Kα emission of the persistent neutron-star atoll low-mass X-ray binary and type I X-ray burster GX 3+1 with the EPIC-PN on board XMM-Newton. The source shows a flux modulation over several years and we observed it during its fainter phase, which corresponds to an X-ray luminosity of LX ~ 1037 erg s-1. When fitted with a two-component model, the X-ray spectrum shows broad residuals at ~6−7 keV that can be ascribed to an iron Kα fluorescence line. In addition, lower energy features are observed at ~3.3 keV, ~3.9 keV and might originate from Ar XVIII and Ca XIX. The broad iron line feature is well fitted with a relativistically smeared profile. This result is robust against possible systematics caused by instrumental pile-up effects. Assuming that the line is produced by reflection from the inner accretion disk, we infer an inner disk radius of ~25Rg and a disk inclination of 35° < i < 44°.
Key words: line: identification / line: profiles / X-rays: individuals: GX 3+1 / X-rays: binaries / stars: neutron
© ESO, 2012
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