A pilot study on the astrometric capability of CSST. Detecting astrometric binaries with Gaia synergy via simulated data
Abstract
The China Space-station Survey Telescope (CSST) will provide deep, wide-field epoch astrometry over its 10-year mission. Accurate recovery of binary orbits requires both high-precision astrometry and sufficient orbital-phase coverage, enabling dynamical constraints on the masses of stellar and compact-object companions. Combining CSST and epoch astrometry extends the temporal baseline and improves orbital phase coverage, thereby enhancing binary detection and orbital characterization. Gaia We evaluate CSST, , and joint epoch astrometry for binary-candidate selection and 12-parameter (12p) orbit fitting at faint magnitudes (g>17.8). We also test how a more regular CSST cadence affects the number of 12p fits satisfying our criteria. Gaia We constructed a mock catalog, simulated CSST and epoch astrometry, and fitted five-parameter (5p) single-star models. We used astrometric diagnostics, proper-motion anomaly features, and observational-sampling features in a four-stage histogram-based gradient-boosting classifier. Selected candidates were then fitted with a 12p orbital model and assessed using two nested selection tiers. Gaia On the independent test set, the classifier reached a precision of 0.802 and a recall among eligible true binaries of 0.181. In the scenario-specific fitted samples, joint astrometry raised the fiducial fraction from 6.76% for alone to 10.46%; for fitted binaries with P_ Gaia ̊m true ̊m yr , it rose from 2.37% to 6.78%. The current CSST schedule yields few fiducial fits, while idealized regular cadences increase the yield mainly at głesssim21. In the simulation, joint CSST and epoch astrometry yields higher fractions of fitted unresolved binaries satisfying the stated criteria than alone. A practical strategy would be to select binary candidates from 5p diagnostics and astrometric anomalies, obtain more regular CSST follow-up observations for promising binaries, and then fit 12p orbital models and apply the selection criteria. Gaia Gaia