Identification of Candidate Millisecond Pulsars from Fermi LAT Observations

TL;DR

This study analyzes 39 Fermi LAT gamma-ray sources to identify candidate millisecond pulsars, finding several promising candidates and providing insights into their multiwavelength properties, but further observations are needed for confirmation.

Contribution

The paper introduces a selection method for candidate MSPs from Fermi LAT data and provides detailed analysis of their gamma-ray and X-ray properties, identifying promising candidates.

Findings

24 sources are point-like and uncontaminated

Three sources are likely MSPs based on previous studies

Most sources have low gamma-ray to X-ray flux ratios

Abstract

We report our detailed data analysis for 39 $\gamma$-ray sources selected from the 992 unassociated sources in the \textit{Fermi} Large Area Telescope (LAT) third source catalog. The selection criteria, which were set for finding candidate millisecond pulsars (MSPs), are non-variables with curved spectra and $>$5$^{\circ}$ Galactic latitudes. From our analysis, 24 sources were found to be point-like sources not contaminated by background or nearby unknown sources. Three of them, J1544.6$-$1125, J1625.1$-$0021, and J1653.6$-$0158, have been previously studied, indicating that they are likely MSPs. The spectra of J0318.1+0252 and J2053.9+2922 do not have properties similar to that of known $\gamma$-ray MSPs, and we thus suggest that they are not MSPs. Analysis of archival X-ray data for most of the 24 sources were also conducted. Four sources were found with X-ray objects in their error circles, and 16 with no detection. The ratios between the $\gamma$-ray fluxes and X-ray fluxes or flux upper limits are generally lower than those of the known $\gamma$-ray MSPs, suggesting that if the $\gamma$-ray sources are MSPs, none of the X-ray objects are the counterparts. Deep X-ray or radio observations of these sources are needed in order to identify their MSP nature.