A comprehensive search for high-velocity X-ray sources: new compact object binary candidates in the Gaia era
Year: 2026
Type: article
Abstract: ABSTRACT We perform a comprehensive search for high-velocity X-ray sources with large X-ray/optical flux ratios ($F_\mathrm{X}/F_\mathrm{G}$), identifying candidates for interacting black hole or neutron star binaries potentially accelerated by supernova natal kicks. We cross-match X-ray points sources from a variety of catalogues (Chandra, XMM–Newton, Swift, and eROSITA) with Gaia DR3. Using Gaia coordinates, parallaxes, and proper motions, we compute peculiar velocities ($\upsilon _\mathrm{pec}$) relative to Galactic disc rotation. Remaining agnostic about radial velocities (RVs), we vary RVs to find the minimum possible $\upsilon _\mathrm{pec}$ values ($\upsilon _\mathrm{pec, min}$). Uncertainties on $\upsilon _\mathrm{pec, min}$ are estimated via Monte Carlo resampling, and we select X-ray sources that have $1\, \sigma$ lower limits on $\upsilon _\mathrm{pec, min}\ge 200\, \mathrm{km~s^{-1}}$ and high $F_\mathrm{X}/F_\mathrm{G}$ values. We show that this velocity threshold excludes most contaminants (e.g. cataclysmic variables and active binaries) while retaining a sensible fraction of compact object binaries, demonstrating that $\upsilon _\mathrm{pec}$ could serve as an effective indicator for the presence of a neutron star or black hole companion. Our selection yields a sample of $2372$ sources, from which we construct a gold sample of $7$ sources that have relatively well-constrained astrometry and confident optical counterparts. Follow-up is necessary to confirm and characterise their high-energy emission, as well as a Galactic disc vs. halo origin.
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $3,046
Funders: National Aeronautics and Space Administration, Engineering Information Foundation Grant, California Institute of Technology, Florida Atlantic University, Australian National Data Service, National Computational Infrastructure, Diabetes Patient Advocacy Coalition, European Space Agency, Leverhulme Trust, Australian National University, Monash University, Swinburne University of Technology, Curtin University of Technology, Jet Propulsion Laboratory, Science and Technology Facilities Council, Australian Research Council, Australian Astronomical Optics-Macquarie, National Cancer Institute
OpenAlex ID: W7120061395