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

¹ Université de Toulouse, UPS-OMP, IRAP, 31028 Toulouse, France
e-mail: Natalie.Webb@irap.omp.eu
² CNRS, IRAP, 9 avenue du Colonel Roche, BP 44346, 31028 Toulouse Cedex 4, France
³ Max-Planck Institute für extraterr. Physik, Giessenbachstrasse 1, 85741 Garching, Germany
⁴ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
⁵ Laboratoire de Physique et Chimie de l’Environnement et de l’Espace LPC2E CNRS-Université d’Orléans, 45071 Orléans Cedex 2, France
⁶ Station de radioastronomie de Nançay, Observatoire de Paris, CNRS/INSU, 18330 Nançay, France
⁷ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
⁸ School of Physics and Astronomy, University of Southampton, Highfield, Southampton SO17 1BJ, UK
⁹ Department of Physics, Royal Institute of Technology, AlbaNova, 10691 Stockholm, Sweden
¹⁰ The Oskar Klein Centre for Cosmoparticle Physics, AlbaNova, 10691 Stockholm, Sweden
¹¹ Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey, RH5 6NT, UK
¹² Institute of Astronomy, University of Zielona Góra, Lubuska 2, 65-265 Zielona Góra, Poland
¹³ Institut de Ciencies de l’Espai (CSIC-IEEC), Campus UAB, Facultat de Ciencies, Torre C5-parell, 2a planta, 08193 Bellaterra (Barcelona), Spain

Received: 16 August 2011
Accepted: 28 April 2012

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 $\mathrm{\Gamma }\mathrm{=}\mathrm{2.1}{\mathrm{0}}_{-0.85}^{\mathrm{+}\mathrm{1.24}}$. 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 $\mathit{kT}\mathrm{=}\mathrm{0.1}{\mathrm{5}}_{-0.04}^{\mathrm{+}\mathrm{0.04}}$ and 0.88$\begin{array}{}\mathrm{+}\mathrm{2.54}\\ -0.54\end{array}$ keV or a blackbody with similar temperature to the previous cooler component, $\mathit{kT}\mathrm{=}\mathrm{0.1}{\mathrm{3}}_{-0.02}^{\mathrm{+}\mathrm{0.04}}$ keV and a power law component with a photon index $\mathrm{\Gamma }\mathrm{=}\mathrm{1.2}{\mathrm{5}}_{-1.75}^{\mathrm{+}\mathrm{2.30}}$. 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.