Unassociated Fermi-LAT sources seen with eROSITA

Our method combines the overlap of X-ray and gamma-ray source positions with a probabilistic classification (into pulsar and blazar candidates) of each source based on its gamma-ray properties and a prediction on the X-ray flux of pulsar- or blazar-type counterparts. Finally, an optical and infrared counterpart search is performed to exclude coronally emitting stars and active galactic nuclei from our catalog. We provide a catalog of our prior gamma-ray-based classifications of all 2600 unassociated sources in the Fermi-LAT catalog, with around equal numbers of pulsar and blazar candidates.

Our final list of candidate X-ray counterparts to suspected new high-energy pulsars, cleaned for spurious detections and sources with obvious non-pulsar counterparts, contains around 900 X-ray sources, the vast majority of which lies in the 95% gamma-ray error ellipse. We predict between 30 and 40 new pulsars among our top 200 candidates, with around equal numbers of young and recycled pulsars. This candidate list may serve as input to future follow-up campaigns, looking directly for pulsations or for the orbital modulation of possible binary companions, where it may allow for a drastic reduction in the number of candidate locations to search.

We furthermore detect the X-ray counterparts of 15 known rotation-powered pulsars, which were not seen in X-rays before.