Hunting for Compact Object Binaries from eRASS1 Optical Counterparts through ZTF Time-domain Photometry and Multiwavelength Surveys

Abstract Capitalizing on the eRASS1 optical counterpart catalog, we conduct a systematic search for compact object binary (COB) candidates, with a primary focus on X-ray binaries (XRBs), by integrating Zwicky Transient Facility (ZTF) time-domain photometry with multiwavelength data. This framework establishes two independent pipelines, yielding two samples. The first sample consists of 151 periodically variable sources, from which a highly refined subset of 43 high-priority COB candidates is identified. The second sample comprises 1958 distance-constrained sources selected on the basis of their elevated X-ray luminosities or high log ( F X / F opt ) values. Crucially, cross-matching both samples with radio catalogs reveals seven radio-emitting sources, highlighting four promising XRB candidates. Our results underscore that coupling eROSITA with wide-field time-domain photometric and multiwavelength surveys offers a highly efficient strategy for uncovering the hidden population of COBs.