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arXiv · 2101.09989

Middle aged $\gamma$-ray pulsar J1957+5033 in X-rays: pulsations, thermal emission and nebula

D. A. Zyuzin·A. V. Karpova·Y. A. Shibanov·A. Y. Potekhin·V. F. Suleimanov
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Abstract

We analyze new XMM-Newton and archival Chandra observations of the middle-aged $\gamma$-ray radio-quiet pulsar J1957+5033. We detect, for the first time, X-ray pulsations with the pulsar spin period of the point-like source coinciding by position with the pulsar. This confirms the pulsar nature of the source. In the 0.15--0.5 keV band, there is a single pulse per period and the pulsed fraction is $\approx18\pm6$ per cent. In this band, the pulsar spectrum is dominated by a thermal emission component that likely comes from the entire surface of the neutron star, while at higher energies ($\gtrsim0.7$ keV) it is described by a power law with the photon index $\Gamma \approx 1.6$. We construct new hydrogen atmosphere models for neutron stars with dipole magnetic fields and non-uniform surface temperature distributions with relatively low effective temperatures. We use them in the spectral analysis and derive the pulsar average effective temperature of $\approx(2-3)\times10^5$ K. This makes J1957+5033 the coldest among all known thermally emitting neutron stars with ages below 1 Myr. Using the interstellar extinction--distance relation, we constrain the distance to the pulsar in the range of 0.1--1 kpc. We compare the obtained X-ray thermal luminosity with those for other neutron stars and various neutron star cooling models and set some constraints on latter. We observe a faint trail-like feature, elongated $\sim 8$ arcmin from J1957+5033. Its spectrum can be described by a power law with a photon index $\Gamma=1.9\pm0.5$ suggesting that it is likely a pulsar wind nebula powered by J1957+5033.

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D. A. Zyuzin, A. V. Karpova, Y. A. Shibanov, A. Y. Potekhin, V. F. Suleimanov. 2021-01-25. Middle aged $\gamma$-ray pulsar J1957+5033 in X-rays: pulsations, thermal emission and nebula. https://doi.org/10.1093/mnras/staa3991

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