Evidence for Surface Cooling Emission in the XMM-Newton Spectrum of the X-Ray Pulsar PSR B2334+61

Abstract

We report on the first XMM-Newton observation of the Vela-like pulsar PSR B2334+61. Spectral analysis reveals soft X-ray emission, with the bulk of the photons emitted at energies below ~1.5 keV. We find that the spectrum has a thermal origin and is well-fitted with either a blackbody or a magnetized, pure H atmospheric model. In the latter case, for a neutron star with a radius of 13 km and a magnetic field of 10¹³ G, the best fit gives a hydrogen column density N_H=0.33×10²² cm^-2 and an effective temperature T^∞_eff=0.65×10⁶ K, as measured at Earth. A comparison of the surface temperature of PSR B2334+61 obtained from this fit with cooling curves favors a medium-mass neutron star with M~1.45 M_solar or M~1.6 M_solar, depending on which of two different models of proton superfluidity in the interior is used. We do not detect any pulsed emission from the source and determine an upper limit of 5% for the modulation amplitude of the emission on the pulsar's radio frequency.