[Submitted on 13 Oct 2022]

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    Abstract: 3XMM J185246.6+003317 is a slowly rotating soft-gamma repeater (neutron star)
    in the vicinity of the supernova remnant Kes\,79. So far, observations have
    only set upper limits to its surface magnetic field and spindown, and there is
    no estimate for its mass and radius. Using ray-tracing modelling and Bayesian
    inference for the analysis of several light curves spanning a period of around
    three weeks, we have found 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 light
    curves, we estimate the surface magnetic field and the mass to be $\log_{10}
    (B/{\rm G}) = 11.89^{+0.19}_{-0.93}$ and $M=2.09^{+0.16}_{-0.09}$~$M_{\odot}$
    at $1\sigma$ confidence level, while the radius is estimated to be
    $R=12.02^{+1.44}_{-1.42}$ km at $2\sigma$ confidence level. The robustness of
    these estimates was verified by simulations, i.e., data injections with known
    model parameters, and their subsequent recovery. The best-fit model has three
    small hot spots, two of them in the southern hemisphere. 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
    hydrogen/helium diffusive nuclear burning. Finally, we briefly discuss some
    consequences of our findings for superdense matter constraints.

    Submission history

    From: Jaziel Goulart Coelho [view email]

    Thu, 13 Oct 2022 01:07:47 UTC (2,554 KB)

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