Searching for Gamma-Ray Millisecond Pulsars: Selection of Candidates Revisited

Abstract

We are starting a project to find $\gamma$-ray millisecond pulsars (MSPs) among the unidentified sources detected by the Large Area Telescope (LAT) onboard the {Fermi Gamma-Ray Space Telescope (Fermi)}, by radio observations. The selection of good candidates from analysis of the LAT data is an important part of the project. Given that there is more than 10 years worth of LAT data and the advent of the newly released LAT 8-year point source list (FL8Y), we have conducted a selection analysis, on the basis of our previous analysis, and report the results here. Setting the requirements for the unidentified sources in FL8Y of Galactic latitudes $|b|>$ 5${}^{\circ }$ and curvature significances $>$3$\sigma$, there are 202 sources with detection signficances $>$6$\sigma$. We select 57 relatively bright ones (detection significances $>$15$\sigma$) and analyze their 10.2 years of LAT data. Their variability is checked to exclude variable sources (likely~blazars), test statistic maps are constructed to avoid contaminated sources, and curvature significances are re-obtained and compared to their $\gamma$-ray spectra to exclude non-significant sources. In the end, 48 candidates are found. Based on the available information, mostly from multi-wavelength studies, we discuss the possible nature of several of the candidates. Most of these candidates are currently being observed with the 65-meter Shanghai Tian Ma Radio Telescope.

arXiv comment10 Pages, 3 Figures, 4 Tables, Published in Galaxies, Special Issue "Observations of Gamma-Ray Pulsars"

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