SED and Galactic kinematic diagnostics for dormant BH/NS binary candidates

TL;DR

This study uses Gaia DR3 data to identify dormant black hole and neutron star binary candidates by analyzing their spectral energy distributions and galactic motions, highlighting 182 prime candidates for further observation.

Contribution

It introduces a combined ultraviolet and kinematic diagnostic approach to refine the identification of dormant compact-object binaries from Gaia data.

Findings

Identified 182 high-priority candidates for follow-up.

Discovered 19 black hole candidates with companion masses ≥ 3 solar masses.

Used ultraviolet excess and galactic kinematics to improve candidate selection.

Abstract

The third data release of the Gaia mission (Gaia DR3) has enabled large-scale searches for dormant black hole and neutron star binaries with stellar companions at AU-scale separations. A recent study has proposed thousands of dormant black hole and neutron star binary candidates using summary statistics from Gaia DR3 by simulating and fitting Gaia observables. In this work, we perform broadband spectral energy distribution (SED) fitting from the optical to the infrared for 1,328 candidates, incorporating GALEX ultraviolet photometry to assess the presence of hidden hot companions. We quantify ultraviolet excess by comparing observed near-ultraviolet fluxes with single-star SED predictions and further test whether excesses can be explained by non-degenerate stellar companions for sources exhibiting moderate excess. We additionally examine the Galactic kinematics of the sample to identify systems potentially affected by natal kicks during compact-object formation. By combining the ultraviolet and kinematic diagnostics, we identify 182 sources as the highest-priority candidates for follow-up observations, in which 19 are black hole candidates with fit_companion_mass $\geq$ 3 $M_\odot$.