Photometric Study of the Fastest-rotating Near-Earth Asteroid 2024 XA1

Abstract

Near-Earth asteroid 2024 XA1 was discovered on 2024 December 3 at 05:55 UT by the 2.3 m Bok Telescope of the University of Arizona. At 07:50 UT on the same day, subsequent orbit refinement confirmed a 100% impact probability, with atmospheric entry predicted at approximately 16:15 UT over eastern Siberia. We obtained observations of 2024 XA1 with the Lijiang 2.4 m telescope in the final ∼1 hr prior to its atmospheric entry. Due to the fact that sidereal tracking was used, the asteroid appears as a long bright trail in each exposure. We developed a method to extract light curves from asteroid trails in such trailed images and evaluate the reconstruction quality by comparing the observed trail image with the model image generated from the recovered light curve. Applying this approach to 2024 XA1 we successfully extracted its light curve. We found that the light curves of 2024 XA1 exhibit a double-peaked structure with two maxima and two minima per cycle. We derived a double-peaked rotation period of Prot=1.63−0.04+0.06s and a peak-to-peak relative flux amplitude of about 46%. This period would make 2024 XA1 the fastest-rotating near-Earth object currently known.