VizieR Online Data Catalog: X-ray/UV/opt counterparts of 4FGL gamma-ray sources (Kerby+, 2021)

The unassociated sources of the Fermi-LAT 4FGL catalog are comprised of gamma-ray sources of unknown astrophysical nature and no known counterpart (see Abdollahi+ 2020, J/ApJS/247/33).

After 10 continuous years of observations, the 4FGL-DR2 catalog (Ballet+ 2020arXiv200511208B) contains 5064 sources in total, of which over 1300 are unassociated; 1410 4FGL sources are targets for the Swift-XRT survey of unassociated sources. By observing the unassociated gamma-ray sources, the Swift program provides high-resolution X-ray, UV, and visual observations to find lower-energy counterparts to the unassociated sources. This survey is a further development after previously analyzing unassociated 3FGL sources (detailed in Kerby+ 2021, J/AJ/161/154) and has covered approximately 500 4FGL unassociated targets with >4ks of observations each.

So far Swift has detected possible X-ray counterparts within the Fermi-LAT uncertainty ellipse of 208 4FGL unassociated sources, with some unassociated sources having multiple possible X-ray counterparts.

(2 data files).