Dense-photometry Validation of Superfast-rotating Asteroid Candidates

Abstract Superfast rotators (SFRs; P < 2.2 hr) are of great importance in asteroid studies; yet, many reported detections suffer from aliasing caused by an insufficient observation cadence. We present dense CCD photometry for 15 SFR candidates (14 after excluding 11219 Benbohn, whose published period already exceeds the spin barrier) observed from 2023 August 11 to 2024 August 11 with the 1.5 m Sierra Nevada and 1.4 m Astronomical Station of Vidojevica telescopes. Our data set comprises approximately 2400 calibrated data points, with per-measurement formal errors of 0.02–0.04 mag and total on-target coverage of 2–13 hr per object. We have reliably determined periods for nine targets. In terms of spin rate, we have confirmed four SFRs with periods of 1.06–1.84 hr and peak-to-peak amplitudes of 0.054–0.685 mag. Three candidates remain ambiguous, while the rest are reclassified, showing the best solutions with periods greater than 2.5 hr. Extrapolating from our confirmation rate (4/14) to the 3.9% occurrence rate found in the Light Curve Database yields a central SFR fraction of 1.1%, with a 1 σ lower bound of 0.6% among kilometer-scale asteroids.