On the X-ray emission mechanisms of the persistent source and very low-fluence bursts of SGR J0501+4516

TL;DR

This study analyzes the X-ray emission of SGR J0501+4516, revealing detailed properties of its persistent emission and faint bursts, including magnetic field strength, surface temperature, and evidence of cooling during bursts.

Contribution

It provides the first detailed spectral analysis of both persistent and low-fluence burst emissions of SGR J0501+4516 using physically motivated models.

Findings

Surface magnetic field strength of 2.2×10^14 G

Surface temperature of 0.38 keV during persistent emission

Burst temperature of 1.16 keV with evidence of cooling

Abstract

We present here a detailed spectral study of the X-ray emission of the persistent source and the low-fluence bursts of SGR J0501+4516 observed during a deep XMM-Newton observation near the peak of its 2008 outburst. For the persistent emission we employ a physically motivated continuum emission model and spectroscopically determine important source properties; such as, the surface magnetic field strength and the magnetospheric scattering optical depth. We find that the magnetar surface temperature near the peak of its activity is 0.38 keV, corresponding to an emission area of 131 km^2 at a distance of 2 kpc. The surface magnetic field strength determined spectroscopically, B=2.2E14 G, is consistent with the dipole field strength inferred from the source spin and spin down rate. We fit the stacked spectra of 129 very faint bursts with a modified blackbody model and find a temperature of 1.16 keV, corresponding to an emission area of 93 km^2. We also find an evidence for cooling during the burst decay phase.