[U-06_28PM2] New Progress toward the Understanding of Small Solar System Bodies

[U06-19] Lightcurve Survey of Vestoids in the Inner Asteroid Belt

*Sunao HASEGAWA¹, Seidai MIYASAKA², Hiroyuki MITO³, Yuki SARUGAKU¹, Tomohiko OZAWA⁴, Daisuke KURODA⁵, Michitoshi YOSHIDA⁶, Kenshi YANAGISAWA⁵, Yasuhiro SHIMIZU⁵, Shogo NAGAYAMA⁵, Hiroyuki TODA⁵, Kouji OKITA⁵, Nobuyuki KAWAI⁷, Tomohiko SEKIGUCHI⁸, Masateru ISHIGURO⁹, Masanao ABE¹ (1.Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 2.Tokyo Metropolitan Government, 3.Kiso Observatory, Institute of Astronomy, The University of Tokyo, 4.Misato Observatory, 5.Okayama Astrophysical Observatory, National Astronomical Observatory, 6.Hiroshima Astrophysical Science Center, Hiroshima University, 7.Graduate School of engineering, , Tokyo Institute of Technology, 8.Asahikawa Campus, Hokkaido University of Education, 9.Department of Physical and Astronomy, Seoul National University)

Keywords:asteroid, vesta

We have made the lightcurve observation of 13 vestoids ((1933) Tinchen, (2011) Veteraniya, (2508) Alupka, (3657) Ermolova, (3900) Knezevic, (4005) Dyagilev, (4383) Suruga, (4434) Nikulin, (4796) Lewis, (6331) 1992 FZ₁, (8645) 1998 TN, (10285) Renemichelsen, and (10320) Reiland). Lightcurves in the R-band of rotation periods were found for (1933) Tinchen, (2011) Veteraniya, (2508) Alupka, (3657) Ermolova, (3900) Knezevic, (4005) Dyagilev, (4383) Suruga, (4796) Lewis, (6331) 1992 FZ₁, (8645) 1998 TN, and (10320) Reiland.The distribution of rotational rates of 59 vestoids in the inner main belt, including 29 members of the Vesta family that are regarded as ejecta from the asteroid (4) Vesta, is inconsistent with the best-fit Maxwellian distribution. This inconsistency may be due to the effect of thermal radiation Yarkovsky- O'Keefe-Radzievskii-Paddack (YORP) torques, and implies that the collision event that formed vestoids is sub-billion to several billion years in age.