Distribution of shape elongations of main belt asteroids derived from Pan-STARRS1 photometry

¹ Institute of Astronomy, Faculty of Mathematics and Physics, Charles University, V Holešovičkách 2, 180 00 Prague 8, Czech Republic
e-mail: cibulkova@sirrah.troja.mff.cuni.cz
² Department of Mathematics, Tampere University of Technology, PO Box 553, 33101 Tampere, Finland
³ Harvard-Smithsonian Center for Astrophysics, 60 Garden St, Cambridge, MA 02138, USA
⁴ Institute for Astronomy University of Hawaii, 2680 Woodlawn Dr, Honolulu, HI 96822, USA
⁵ Department of Physics and Astronomy, PO Box 6010, Northern Arizona University, Flagstaff, AZ 86011, USA

Received: 12 July 2017
Accepted: 10 September 2017

Abstract

Context. A considerable amount of photometric data is produced by surveys such as Pan-STARRS, LONEOS, WISE, or Catalina. These data are a rich source of information about the physical properties of asteroids. There are several possible approaches for using these data. Light curve inversion is a typical method that works with individual asteroids. Our approach in focusing on large groups of asteroids, such as dynamical families and taxonomic classes, is statistical; the data are not sufficient for individual models.

Aim. Our aim is to study the distributions of shape elongation b∕a and the spin axis latitude β for various subpopulations of asteroids and to compare our results, based on Pan-STARRS1 survey, with statistics previously carried out using various photometric databases, such as Lowell and WISE.

Methods. We used the LEADER algorithm to compare the b∕a and β distributions for various subpopulations of asteroids. The algorithm creates a cumulative distributive function (CDF) of observed brightness variations, and computes the b∕a and β distributions with analytical basis functions that yield the observed CDF. A variant of LEADER is used to solve the joint distributions for synthetic populations to test the validity of the method.

Results. When comparing distributions of shape elongation for groups of asteroids with different diameters D, we found that there are no differences for D < 25 km. We also constructed distributions for asteroids with different rotation periods and revealed that the fastest rotators with P = 0 − 4 h are more spheroidal than the population with P = 4−8 h.