XMM-Newton observations of a gamma-ray pulsar J0633+0632: pulsations, cooling and a large-scale emission

Andrey Danilenko, Anna Karpova, Dmitry Ofengeim, Yury Shibanov, Dmitry Zyuzin

Published 2020-01-29Version 1

We report results of XMM-Newton observations of a $\gamma$-ray pulsar J0633+0632 and its wind nebula. We reveal, for the first time, pulsations of the pulsar X-ray emission with a single sinusoidal pulse-profile and a pulsed fraction of $23\pm6$ per cent in the 0.3--2 keV band. We confirm previous Chandra findings that the pulsar X-ray spectrum consists of a thermal and a non-thermal components. However, we do not find the absorption feature that was previously detected at about 0.8 keV. Thanks to larger sensitivity of XMM-Newton, we get stronger, as compared to previous studies, constraints on spectral model parameters. The thermal component can be equally well described by either blackbody or neutron star's atmosphere models implying that this emission is coming from either hot, with temperature of about 120 eV, pulsar polar caps or from a colder, with temperature of about 50 eV, bulk of the neutron star surface. In the latter case, the pulsar appears to be one of the coolest among other neutron stars of similar ages with estimated surface temperatures. We discuss cooling scenarios relevant to this neutron star. Using an interstellar absorption--distance relation, we also constrain the distance to the pulsar being in the range of 0.7--2 kpc. Besides the pulsar and its compact nebula, we detect regions of weak large-scale diffuse non-thermal emission in the pulsar field and discuss their possible nature.