Adam Waszczak (Caltech) -- Asteroid lightcurves in the Palomar Transient Factory survey

Using sparse photometry from the Palomar Transient Factory (PTF) survey, we fit a combined rotation-curve plus phase-function model to ~54,000 asteroid light curves, each light curve consisting of at least 20 observations in a single broadband filter within a single opposition. We assess the accuracy of our fitted rotation periods using 805 asteroids in our sample which have confident previously-measured periods in the literature. Using the 805-asteroid ground-truth sample, we train an automated classifier to estimate (in conjunction with manual inspection) the reliability of the remaining ~53,000 fitted periods. By this method we find ~9,000 of our fitted lightcurves (of ~8,300 unique asteroids) have `reliable' periods. We show that the distribution of these reliable rotation frequencies is non-Maxwellian (with excess slow and fast rotators) as found by previous studies. For lightcurves having sufficient phase-angle coverage and either a reliably-fit period or a low-amplitude rotation curve, we examine the variation in several phase-function parameters as a function of asteroid taxonomy. In particular, we introduce a numerical taxonomic index derived from a uniform clustering analysis applied to seven visible-color asteroid surveys. This taxonomic metric quantifies an asteroid's position in the one-dimensional space spanning the C-type and S-type end-member complexes, thereby permitting uniform comparison of data from the seven color surveys. We find that all three commonly-used phase-function parameters correlate with this taxonomic index, as found by previous studies. We interpret this relationship, as well as the relationship between visible albedo and phase-function parameters.