Hunting for Compact Object Binaries from eRASS1 Optical Counterparts through ZTF Time-domain Photometry and Multi-wavelength Census

Abstract

Capitalizing on the eRASS1 optical counterpart catalog, we conduct a systematic census of compact object binary (COB) candidates, with a primary focus on X-ray binaries (XRBs), by integrating ZTF time-domain photometry with multi-wavelength observations. This framework establishes two complementary pipelines, yielding two distinct source 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 based on elevated X-ray luminosities or high $\log (F_{\mathrm{X}}/F_{\mathrm{opt}})$. 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 multi-wavelength surveys offers a highly efficient strategy for uncovering the hidden population of COBs.