Photometric survey, modelling, and scaling of long-period and low-amplitude asteroids

Abstract

The available set of spin and shape modelled asteroids is strongly biased against slowly rotating targets and those with low lightcurve amplitudes. As a consequence of these selection effects, the current picture of asteroid spin axis distribution, rotation rates, or radiometric properties, might be affected too. To counteract these selection effects, we are running a photometric campaign of a large sample of main belt asteroids omitted in most previous studies. We determined synodic rotation periods and verified previous determinations. When a dataset for a given target was sufficiently large and varied, we performed spin and shape modelling with two different methods. We used the convex inversion method and the non-convex SAGE algorithm, applied on the same datasets of dense lightcurves. Unlike convex inversion, the SAGE method allows for the existence of valleys and indentations on the shapes based only on lightcurves. We obtained detailed spin and shape models for the first five targets of our sample: (159) Aemilia, (227) Philosophia, (329) Svea, (478) Tergeste, and (487) Venetia. When compared to stellar occultation chords, our models obtained an absolute size scale and major topographic features of the shape models were also confirmed. When applied to thermophysical modelling, they provided a very good fit to the infrared data and allowed their size, albedo, and thermal inertia to be determined. Convex and non-convex shape models provide comparable fits to lightcurves. However, some non-convex models fit notably better to stellar occultation chords and to infrared data in sophisticated thermophysical modelling (TPM). In some cases TPM showed strong preference for one of the spin and shape solutions. Also, we confirmed that slowly rotating asteroids tend to have higher-than-average values of thermal inertia.

Accepted in astronomy astrophys. 39 pages, 49 figures

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• Small Bodies: Near and Far Database for thermal infrared observations of small bodies in the Solar System
• Thermal properties of large main-belt asteroids observed by Herschel PACS
• Thermophysical Investigation of Asteroid Surfaces II: Factors Influencing Grain Size
• $V$-band photometry of asteroids from ASAS-SN: Finding asteroids with slow spin
• Properties of slowly rotating asteroids from the Convex Inversion Thermophysical Model
• Volume uncertainty assessment method of asteroid models from disk-integrated visual photometry
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• Scaling slowly rotating asteroids by stellar occultations
• Light curves of transneptunian objects from the K2 mission of the Kepler Space Telescope
• Physical parameters of selected Gaia mass asteroids
• Asteroid sizes determined with thermophysical model and stellar occultations