Rotation Period Analysis and Search for Complex Rotational States in LSST-Reported Asteroids

The Legacy Survey of Space and Time (LSST) conducted by the Vera C. Rubin Observatory is expected to provide unprecedented time-domain photometric datasets for Solar System objects. In this study, we investigate whether photometric observations from the LSST reported to the Minor Planet Center can be used to identify complex rotational states of asteroids. Using the dataset updated on Apr. 15, 2026, we identified 69 asteroids with more than 500 reported photometric measurements (Fig. 1), offering relatively dense sampling compared to typical asteroid lightcurves.

We search for rotation periods using Fourier-based lightcurve analysis and inspect the phased lightcurves for non-periodic behavior potentially associated with tumbling rotation or binary systems. Our focus is on irregular amplitudes, multi-periodic variations, and mutual-event-like features.

As a test case, we investigate the known main-belt binary asteroid (7344) Summerfield. Long-term dense photometric observations obtained from Bohyunsan Optical Astronomy Observatory (BOAO), Lemmonsan Optical Astronomy Observatory (LOAO), Sobaeksan Optical Astronomy Observatory (SOAO), and archival datasets were combined with photometric observations from the LSST acquired during similar epochs to examine how binary-related lightcurve structures may appear within the LSST dataset.

Our goal is to evaluate the effectiveness of LSST observations for identifying complex rotational states and potential binary asteroid candidates within large photometric datasets.

Figure 1. Distribution of asteroids by the number of photometric observations in the LSST asteroid dataset updated on Apr. 15, 2026. The highlighted region indicates 69 asteroids with more than 500 observations, selected for rotational period and complex variability analyses.