A search for counterparts of γ-ray pulsars detected by the FERMI Large Area Telescope

Aims. A group of new γ−ray pulsars has recently been detected by FERMI Large Area Telescope (LAT) in a blind search. In this paper, we report the results from searching for the multi-wavelength counterparts of these pulsars. Methods. To search for their counterparts, we have cross-correlated the FERMI LAT Bright γ-ray Source List with the XMM-Newton serendipitous source catalogue (SSC), data archives of Chandra and NRAO/VLA Sky Survey as well as USNO-B1.0 optical source catalogue. Results. We report the identification of an X-ray source in the XMM-Newton SSC, 2XMM J202131.0+402645, located within the 95% confidence circle of 0FGL J2021.5+4026. With an independent archival Chandra observation, we do not find any variability of this X-ray source. Together with the non-detection of any associated optical counterpart and its X-ray hardness, we suggest 2XMM J202131.0+402645 to be the only possible X-ray counterpart located in the error circle of 0FGL J2021.5+4026. This identification provides an X-ray position with arc-second accuracy, RA (J2000) = 202130. 553, Dec (J2000) = +40◦26′46. ′′89 (with uncertainties δRA=1.18” and δDec=0.84”), which is helpful in facilitating further investigations. In the radio sky survey data, an elliptical excess as well as an orthogonal jet-like structure have been identified in the error circle of 0FGL J2021.5+4026, which have morphologies similar to that of known pulsar wind nebulae.