Asteroid Spin-rate Study Using the Intermediate Palomar Transient Factory
Two dedicated asteroid rotation-period surveys have been carried out in the R band with ~20 minute cadence using the intermediate Palomar Transient Factory (iPTF) during 2014 January 6–9 and February 20–23. The total survey area covered 174 deg^2 in the ecliptic plane. Reliable rotation periods for 1438 asteroids are obtained from a larger data set of 6551 mostly main-belt asteroids, each with ⩾ 10 detections. Analysis of 1751, PTF-based, reliable rotation periods clearly shows the spin barrier at ~2 hr for rubble-pile asteroids. We found a new large super-fast rotator, 2005 UW163, and another five candidates as well. For asteroids of 3 < D < 15 km, our spin-rate distribution shows a number decrease along with frequency after 5 rev day^(−1), which is consistent with the results of the Asteroid Light Curve Database. The discrepancy between our work and that of Pravec et al. (update 2014 April 20) comes mainly from asteroids with Δm < 0.2 mag, which could be the result of different survey strategies. For asteroids with D < 3 km, we see a significant number drop at f = 6 rev day^(−1). The relatively short YORP effect timescale for small asteroids could have spun up those elongated objects to reach their spin-rate limit resulting in breakup to create such a number deficiency. We also see that the C-type asteroids show a smaller spin-rate limit than the S-type, which agrees with the general impression that C-type asteroids have a lower bulk density than S-type asteroids.
© 2015 The American Astronomical Society. Received 2015 February 3; accepted 2015 June 27; published 2015 August 11. This work is supported in part by the National Science Council of Taiwan under the grants NSC 101-2119-M-008-007-MY3 and NSC 102-2112-M-008-019-MY3. We thank the referees, Petr Pravec and Alan Harris, for their useful suggestions and comments to improve the content of the paper. This publication makes use of data products from WISE, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, funded by the National Aeronautics and Space Administration. This publication also makes use of data products from NEOWISE, which is a project of the Jet Propulsion Laboratory/California Institute of Technology, funded by the Planetary Science Division of the National Aeronautics and Space Administration. We gratefully acknowledge the extraordinary services specific to NEOWISE contributed by the International Astronomical Unionʼs Minor Planet Center, operated by the Harvard-Smithsonian Center for Astrophysics, and the Central Bureau for Astronomical Telegrams, operated by Harvard University.
Submitted - 1506.08493v1.pdf
Published - Chang_2015.pdf