A pilot study on the astrometric capability of CSST
- 1Shanghai Astronomical Observatory, Chinese Academy of Sciences
Abstract
Context. 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 Gaia epoch astrometry extends the temporal baseline and improves orbital phase coverage, thereby enhancing binary detection and orbital characterization. Aims. We evaluate CSST, Gaia, 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. Methods. We constructed a mock catalog, simulated CSST and Gaia epoch astrometry, and fitted five-parameter (5p) singlestar 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. Results. 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 Gaia alone to 10.46%; for fitted binaries with Ptrue > 15 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 g ≲ 21. Conclusions. In the simulation, joint CSST and Gaia epoch astrometry yields higher fractions of fitted unresolved binaries satisfying the stated criteria than Gaia 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.
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BibTeX
@article{shangyu2026pilot,
title = {{A pilot study on the astrometric capability of CSST}},
author = {Wen Shangyu and Liao Shilong and Qi Zhaoxiang and Fu Zhensen and Peng Xiyan and Ding Ye and Wu Qiqi and Xu Qi and Sun Xun and Zhu Keyu and Yu Yong},
journal = {Astronomy \& Astrophysics},
year = {2026},
month = nov,
doi = {10.1051/0004-6361/202558478},
url = {https://doi.org/10.1051/0004-6361/202558478},
note = {CC BY},
}
RIS
TY - JOUR
TI - A pilot study on the astrometric capability of CSST
AU - Wen Shangyu
AU - Liao Shilong
AU - Qi Zhaoxiang
AU - Fu Zhensen
AU - Peng Xiyan
AU - Ding Ye
AU - Wu Qiqi
AU - Xu Qi
AU - Sun Xun
AU - Zhu Keyu
AU - Yu Yong
PY - 2026
DA - 2026/11/04
JO - Astronomy & Astrophysics
DO - 10.1051/0004-6361/202558478
UR - https://doi.org/10.1051/0004-6361/202558478
AB - Context. 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 Gaia epoch astrometry extends the temporal baseline and improves orbital phase coverage, thereby enhancing binary detection and orbital characterization. Aims. We evaluate CSST, Gaia, 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. Methods. We constructed a mock catalog, simulated CSST and Gaia epoch astrometry, and fitted five-parameter (5p) singlestar 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. Results. 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 Gaia alone to 10.46%; for fitted binaries with Ptrue > 15 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 g ≲ 21. Conclusions. In the simulation, joint CSST and Gaia epoch astrometry yields higher fractions of fitted unresolved binaries satisfying the stated criteria than Gaia 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.
SN - 0004-6361
SN - 1432-0746
ER -