Multiwavelength properties of a new Geminga-like pulsar: PSRJ2021+4026

Abstract

In this paper, we report on a detailed investigation of the multiwavelength properties of a newly detected γ-ray pulsar, PSR J2021+4026, in both observational and theoretical aspects. We first identify an X-ray source in the XMM–Newton serendipitous source catalogue, 2XMM J202131.0+402645, located within the 95 per cent confidence circle of PSR J2021+4026. With an archival Chandra observation, this identification provides an X-ray position with arcsecond accuracy which is helpful in facilitating further investigations. Searching for the pulsed radio emission at the position of 2XMM J202131.0+402645 with a 25-m telescope at Urumqi Astronomical Observatory resulted in null detection and places an upper limit of 0.1 mJy for any pulsed signal at 18 cm. Together with the emission properties in X-ray and γ-ray, the radio quietness suggests PSR J2021+4026 to be another member of Geminga-like pulsars. In the radio sky survey data, extended emission features have been identified in the γ-ray error circle of PSR J2021+4026. We have also re-analysed the γ-ray data collected by Fermi's Large Area Telescope. We found that the X-ray position of 2XMM J202131.0+402645 is consistent with that of the optimal γ-ray timing solution. We have further modelled the results in the context of the outer gap model, which provides us with constraints for the pulsar emission geometry such as the magnetic inclination angle and the viewing angle. We have also discussed the possibility of whether PSR J2021+4026 has any physical association with the supernova remnant G78.2+2.1 (γ-Cygni).