X-ray follow-up observations of the two γ-ray pulsars PSR J1459-6053 and PSR J1614-2230

Abstract

Aims. We have observed two newly detected γ-ray pulsars, PSR J1459-6053 and PSR J1614-2230, in the X-ray domain with XMM-Newton to try to enlarge the sample of pulsars for which multi-wavelength data exist. We use these data with the aim of understanding the pulsar emission mechanisms of these pulsars. Methods. We analysed the X-ray spectra to determine whether the emission emanates from the neutron star surface (thermal emission) or from the magnetosphere (non-thermal emission) and compared this to the region in the magnetosphere in which the γ-ray emission is generated. Furthermore, we compared the phase-folded X-ray lightcurves with those in the γ-ray and, where possible, radio domains, to elicit additional information on the emission sites. Results. J1459-6053 shows X-ray spectra that are best fitted with a power law model with a photon index Γ=2.10 +1.24-0.85. The γ-ray data suggest that either the slot gap or the outer gap model may be best to describe the emission from this pulsar. Analysis of the X-ray lightcurve folded on the γ-ray ephemeris shows modulation at the 3.7σ level in the 1.0-4.5 keV domain. Possible alignment of the main γ-ray and X-ray peaks also supports the interpretation that the emission in the two energy domains emanates from similar regions. The millisecond pulsar J1614-2230 exhibits an X-ray spectrum with a substantial thermal component, where the best-fitting spectral model is either two blackbodies, with kT=0.15 +0.04-0.04 and 0.88 +2.54-0.54 keV or a blackbody with similar temperature to the previous cooler component, kT=0.13 +0.04-0.02 keV and a power law component with a photon index Γ=1.25 +2.30-1.75. The cooler blackbody component is likely to originate from the hot surface at the polar cap. Analysis of the X-ray lightcurve folded on the radio ephemeris shows modulation at the 4.0σ level in the 0.4-3.0 keV domain. © 2012 ESO.