Wide-band Suzaku Analysis of the Persistent Emission from SGR 0501+4516 During the 2008 Outburst

We observed the soft gamma repeater SGR 0501+4516 with Suzaku for ~51 ks on 2008 August 26-27, about 4 days after its discovery. Following the first paper, which reported on the persistent soft X-ray emission and the wide-band spectrum of an intense short burst, this paper presents an analysis of the persistent broadband (1-70 keV) spectra of this source in outburst, taken with the X-ray Imaging Spectrometer (XIS) and the Hard X-ray Detector (HXD). Pulse-phase folding in the 12-35 keV HXD-PIN data on an ephemeris based on multi-satellite timing measurements at soft X-rays revealed the pulsed signals at gsim99% confidence in the hard X-ray band. The wide-band spectrum clearly consists of a soft component and a separate hard component, crossing over at ~7 keV. When the soft component is modeled by a blackbody plus a Comptonized blackbody, the hard component exhibits a 20-100 keV flux of 4.8+0.8 -0.6(stat.)+0.8 -0.4(sys.) × 10-11 erg s-1 cm-2 and a photon index of Γ = 0.79+0.20 -0.18(stat.)+0.01 -0.06(sys.). The hard X-ray data are compared with those obtained by INTEGRAL about 1 day later. Combining the present results with those on other magnetars, we discuss a possible correlation between the spectral hardness of magnetars and their characteristic age and magnetic field strengths.