Investigating the most promising Yarkovsky candidates using Gaia DR2 astrometry

Abstract

The Yarkovsky drift is a major factor driving the orbital evolution of asteroids. To date, the effect has been detected for a few hundred asteroids, mainly near-Earth objects. Before the start of the European Space Agency Gaia mission, the expectation was to recognize many other asteroids manifesting the Yarkovsky drift through the high precision and accuracy of the Gaia astrometry. In this work, we investigated the most promising Yarkovsky candidates indexed before the start of the mission. We found a reliable detection with signal-to-noise (SNR) ratio ¿ 3 of the Yarkovsky effect (A2) for 12 asteroids. When compared to analytical theory from the literature using known (or assumed) orbital and physical parameters, we find that 7–10 (depending on the cutoff value) out of 12 asteroids with SNR ¿3 are consistent with the estimated analytical drift values. In 17 cases, the resulting A2-parameter signal-to-noise was increased with the usage of the Gaia DR2 catalogue data, but no reliable detection can yet be claimed. We are certain that subsequent releases of the Gaia data will lead to numerous other detections. The Yarkovsky drift detection potential of the Gaia data is highlighted for asteroids such as (66391) Moshup (with a previously detected Yarkovsky drift) for which we noted a sizeable increase of the A2 signal-to-noise ratio from ∼2.5 to ∼13 when using the DR2 data compared to when using only the Minor Planet Center astrometry.