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

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 $\approx 18\pm 6$ 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 ($\gtrsim 0.7$ 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 $\approx (2-3)\times 10^5$ 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 $\Gamma =1.9\pm 0.5$ suggesting that it is likely a pulsar wind nebula powered by J1957+5033.

14 pages, 13 figures, published in MNRAS

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Cited by in corpus (7)

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• Two-blackbody portraits of radiation from magnetized neutron stars
• XMM-Newton observations of PSR J0554+3107: pulsing thermal emission from a cooling high-mass neutron star
• Likely optical counterpart of the cool middle-aged pulsar J1957+5033
• A Simple Model of Radiation from a Magnetized Neutron Star: Accreted Matter and Polar Hotspots