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arXiv · 2208.06160

XMM-Newton observations of PSR J0554+3107: pulsing thermal emission from a cooling high-mass neutron star

A. S. Tanashkin·A. V. Karpova·A. Y. Potekhin·Y. A. Shibanov·D. A. Zyuzin
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Abstract

XMM-Newton observations of the middle-aged radio-quiet $γ$-ray pulsar J0554+3107 allowed us, for the first time, firmly identify it in X-rays by detection of pulsations with the pulsar period. In the 0.2-2 keV band, the pulse profile shows two peaks separated by about a half of the rotation phase with the pulsed fraction of $25 \pm 6$ per cent. The profile and spectrum in this band can be mainly described by thermal emission from the neutron star with the hydrogen atmosphere, dipole magnetic field of $\sim 10^{13}$ G and non-uniform surface temperature. Non-thermal emission from the pulsar magnetosphere is marginally detected at higher photon energies. The spectral fit with the atmosphere+power law model implies that J0554+3107 is a rather heavy and cool neutron star with the mass of 1.6-2.1 $M_\odot$, the radius of $\approx 13$ km and the redshifted effective temperature of $\approx 50$ eV. The spectrum shows an absorption line of unknown nature at $\approx 350$ eV. Given the extinction-distance relation, the pulsar is located at $\approx 2$ kpc and has the redshifted bolometric thermal luminosity of $\approx 2 \times 10^{32}$ erg s$^{-1}$. We discuss cooling scenarios for J0554+3107 considering plausible equations of state of super-dense matter inside the star, different compositions of the heat-blanketing envelope and various ages.

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A. S. Tanashkin, A. V. Karpova, A. Y. Potekhin, Y. A. Shibanov, D. A. Zyuzin. 2022-08-12. XMM-Newton observations of PSR J0554+3107: pulsing thermal emission from a cooling high-mass neutron star. https://doi.org/10.1093/mnras%2Fstac2164

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