Dormant black hole candidates from Gaia DR3 summary diagnostics -- supplementary material

Candidate dormant black hole and neutron star binaries identified using summary statistics from Gaia DR3. Here, we provide the results from applying our forward-modelling framework of Gaia summary diagnostics to stars showing excess scatter in RV and position in DR3. For all candidates, we inferred posterior distributions for companion mass and orbital period by simulating and fitting Gaia observables, in particular the renormalised unit weight error (ruwe) and radial velocity (RV) scatter, marginalising over nuisance orbital parameters. The sample is split into two catalogues; the main catalogue of 21,028 RGB stars and the supplementary catalogue of 19,664 MS stars. Each catalogue contains the inferred orbital periods and companion masses and quality flags to filter unreliable sources, as explained in more detail in Müller-Horn et al. (2025). The subset of the most promising BH candidates can be selected by requiring fit_companion_mass > 3.0 and flag_quality == True, yielding 389 RGB+BH candidates and 279 MS+BH candidates, respectively. For all stars, we include the most relevant Gaia DR3 data as well as the assumed primary star masses and radii. Parameter Description Fundamental Parameters designation Gaia DR3 designation source_id Gaia DR3 source identifier ra, dec Gaia DR3 right ascension and declination (deg) parallax, parallax_error Gaia DR3 parallax and uncertainty (mas) pmra, pmdec Gaia DR3 propoer motion in right ascension and declination (mas/yr) phot_g_mean_mag Gaia DR3 G-band magnitude phot_g_mean_flux_over_error Gaia DR3 G-band mean flux divided by its error phot_g_n_obs Gaia DR3 number of observations contributing to G photometry phot_bp_mean_mag Gaia DR3 BP-band magnitude phot_rp_mean_mag Gaia DR3 RP-band magnitude ruwe Gaia DR3 renormalised unit weight error rv_amplitude_robust Gaia DR3 total amplitude in the radial velocity time series after outlier removal (km/s) radial_velocity, radial_velocity_error Gaia DR3 radial velocity and uncertainty (km/s) rv_nb_transits Gaia DR3 number of transits used to compute the radial velocity mass Primary star mass (solar mass) for RGB stars: inferred from XGBoost inference for MS stars: SED based, from Li et al. 2025 radius Primary star radius (solar radius) for RGB stars: inferred from XGBoost inference for MS stars: isochrone radius, based on Li et al. 2025 Results from binary model fit of summary diagnostics fit_period, fit_period_errup, fit_period_errlow Binary orbital period and uncertainties (days) fit_companion_mass, fit_companion_mass_errup, fit_companion_mass_errlow Companion mass and uncertainties (solar mass) fit_cosi, fit_cosi_err Cosine of orbital inclination and uncertainty Quality flags mass_significance Fraction of posterior weight for companion mass exceeding three solar masses flag_rv Star removed as RV outlier? (Boolean) flag_parx Star removed because of unreliable parallax? (Boolean) flag_phot Star removed because of photometric variability? (Boolean) flag_nss Star removed becasue of existing NSS orbital solution? (Boolean) flag_quality Whether star remains in final cleaned sample. (Boolean) Update v2: For the final accepted version of the manuscript, we treated parallax as a free parameter in the inference. This allowed parallax uncertainties to be consistently propagated into the inferred orbital parameters and companion masses, which is particularly important for systems with low parallax significance. This change reduced the number of promising RGB+BH candidates from 556 to 389.