One of the most massive soft-gamma repeater stars to date
3XMM J185246.6+003317: an isolated massive neutron star with a low magnetic field and a carbon atmosphere
We present the results of ray-tracing modelling and bayesian inference for the analysis of several light curves spanning a period of around three weeks of 3xmm j185246.6+003317, a slowly rotating soft-gamma repeater (neutron star) in the vicinity of the supernova remnant kes\,79.79.3.Our analysis suggests that it may be one of the most massive neutron stars to date.In addition, our analysis suggests a multipolar magnetic field structure with a subcritical field strength and a carbon atmosphere composition.Due to the time-resolution limitation of the available lightcurves, we estimate the surface magnetic field and the mass to be and at confidence level, while the radius is estimated to be km at confidence level.The robustness of these estimates was verified by simulations, i.e., data injections with known model parameters, and their subsequent recovery.We interpret the above results as due to accretion of supernova layers/interstellar medium onto 3xmm j185246.6+003317 leading to burying and a subsequent re-emergence of the magnetic field, and a carbon atmosphere being formed possibly due to hydrorogen/helium diffusive nuclear burning.Finally, we briefly discuss some consequences of our findings for superdense matter constraints.
MOS 2 raw image for observation 0550670201. The image LUT is in log-scale; units are counts per pixel. Source and background extraction regions for