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Keywords:

  • stars: magnetars;
  • X-rays: individual: SGR 0526-66

ABSTRACT

We present a systematic analysis of all archival Chandra observations of the soft gamma repeater SGR 0526−66. Our results show that the X-ray flux of SGR 0526−66 decayed by about 20 per cent between 2000 and 2009. We employ physically motivated X-ray spectral models and determine the effective temperature and the strength of the magnetic field at the surface as kT= 0.354+0.031−0.024 keV and inline image G, respectively. We find that the effective temperature remains constant within the statistical uncertainties and attribute the decrease in the source flux to a decrease in the emitting radius. We also perform timing analysis to measure the evolution of the spin period and the period derivative over the 9-year interval. We find a period derivative of inline image s s−1, which allows us to infer the dipole magnetic field strength and compare it with the one determined spectroscopically. Finally, we compare the effective temperature of SGR 0526−66 with the expected cooling trends from magnetized neutron stars and suggest an initial magnetic field strength of 1015–1016 G for the source.