FOSSIL. I. The Spin Rate Limit of Jupiter Trojans

Rotation periods of 53 small (diameters 2 km < D < 40 km) Jupiter Trojans (JTs) were derived using the high-cadence lightcurves obtained by the FOSSIL phase I survey, a Subaru/Hyper Suprime-Cam intensive program. These are the first reported periods measured for JTs with D < 10 km. We found a lower limit of the rotation period near 4 hr, instead of the previously published result of 5 hr found for larger JTs. Assuming a rubble-pile structure for JTs, a bulk density of ≈0.9 g cm−3 is required to withstand this spin rate limit, consistent with the value ∼0.8–1.0 g cm−3 derived from the binary JT system, (617) Patroclus–Menoetius system.