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Asteroid Light Curves from the Palomar Transient Factory Survey: Rotation Periods and Phase Functions from Sparse Photometry

Waszczak, Adam and Chang, Chan-Kao and Ofek, Eran O. and Laher, Russ and Masci, Frank and Levitan, David and Surace, Jason and Cheng, Yu-Chi and Ip, Wing-Huen and Kinoshita, Daisuke and Helou, George and Prince, Thomas A. and Kulkarni, Shrinivas (2015) Asteroid Light Curves from the Palomar Transient Factory Survey: Rotation Periods and Phase Functions from Sparse Photometry. Astronomical Journal, 150 (3). Art. No. 75. ISSN 1538-3881.

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We fit 54,296 sparsely sampled asteroid light curves in the Palomar Transient Factory survey to a combined rotation plus phase-function model. Each light curve consists of 20 or more observations acquired in a single opposition. Using 805 asteroids in our sample that have reference periods in the literature, we find that the reliability of our fitted periods is a complicated function of the period, amplitude, apparent magnitude, and other light-curve attributes. Using the 805-asteroid ground-truth sample, we train an automated classifier to estimate (along with manual inspection) the validity of the remaining ~53,000 fitted periods. By this method we find that 9033 of our light curves (of ~8300 unique asteroids) have "reliable" periods. Subsequent consideration of asteroids with multiple light-curve fits indicates a 4% contamination in these "reliable" periods. For 3902 light curves with sufficient phase-angle coverage and either a reliable fit period or low amplitude, we examine the distribution of several phase-function parameters, none of which are bimodal though all correlate with the bond albedo and with visible-band colors. Comparing the theoretical maximal spin rate of a fluid body with our amplitude versus spin-rate distribution suggests that, if held together only by self-gravity, most asteroids are in general less dense than ~2 g cm^(−3), while C types have a lower limit of between 1 and 2 g cm^(−3). These results are in agreement with previous density estimates. For 5–20 km diameters, S types rotate faster and have lower amplitudes than C types. If both populations share the same angular momentum, this may indicate the two types' differing ability to deform under rotational stress. Lastly, we compare our absolute magnitudes (and apparent-magnitude residuals) to those of the Minor Planet Center's nominal (G = 0.15, rotation-neglecting) model; our phase-function plus Fourier-series fitting reduces asteroid photometric rms scatter by a factor of ~3.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Chang, Chan-Kao0000-0003-1656-4540
Ofek, Eran O.0000-0002-6786-8774
Laher, Russ0000-0003-2451-5482
Masci, Frank0000-0002-8532-9395
Surace, Jason0000-0001-7291-0087
Ip, Wing-Huen0000-0002-3140-5014
Helou, George0000-0003-3367-3415
Prince, Thomas A.0000-0002-8850-3627
Kulkarni, Shrinivas0000-0001-5390-8563
Additional Information:© 2015 The American Astronomical Society. Received 2015 March 4; accepted 2015 April 15; published 2015 August 18. This work uses data obtained with the 1.2 m Samuel Oschin Telescope at Palomar Observatory as part of the PTF, a scientific collaboration between the California Institute of Technology (Caltech), Columbia University, Las Cumbres Observatory Global Telescope Network, Lawrence Berkeley National Laboratory, the National Energy Research Scientific Computing Center, the University of Oxford, and the Weizmann Institute of Science (WIS). Some data in this work (also from the 1.2 m Oschin Telescope) were obtained as part of the iPTF project, a collaboration among Caltech, the Kavli Institute for the Physics and Mathematics of the universe, Los Alamos National Laboratory, the Oskar Klein Centre, the University System of Taiwan, the University of Wisconsin Milwaukee, and WIS. A. Waszczak has been supported in part by the W. M. Keck Institute for Space Studies (KISS) at Caltech. E.O.O. is incumbent of the Arye Dissentshik career development chair and is grateful to support by grants from the Willner Family Leadership Institute Ilan Gluzman (Secaucus NJ), Israeli Ministry of Science, Israel Science Foundation, Minerva and the I-CORE Program of the Planning and Budgeting Committee, and The Israel Science Foundation. This work also makes use of data products from the Wide-Field Infrared Survey Explorer, a joint project of the University of California Los Angeles and the Jet Propulsion Laboratory (JPL)/Caltech, funded by NASA. This work also makes use of data from NEOWISE, which is a project of JPL/ Caltech, funded by the Planetary Science Division of NASA. This work also makes use of data from the SDSS, managed by the Astrophysical Research Consortium for the Participating Institutions and funded by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, the US Department of Energy, NASA, the Japanese Monbukagakusho, the Max Planck Society, and the Higher Education Council for England. Lastly, we thank an anonymous reviewer for helpful comments and feedback.
Group:Infrared Processing and Analysis Center (IPAC), Palomar Transient Factory
Funding AgencyGrant Number
W. M. Keck Institute for Space StudiesUNSPECIFIED
Willner Family Leadership Institute Ilan GluzmanUNSPECIFIED
Ministry of Science (Israel)UNSPECIFIED
Israel Science FoundationUNSPECIFIED
I-CORE Program of the Planning and Budgeting CommitteeUNSPECIFIED
Alfred P. Sloan FoundationUNSPECIFIED
Participating InstitutionsUNSPECIFIED
Department of Energy (DOE)UNSPECIFIED
Japanese MonbukagakushoUNSPECIFIED
Max Planck SocietyUNSPECIFIED
Higher Education Funding Council for EnglandUNSPECIFIED
Subject Keywords:minor planets, asteroids: general – surveys
Issue or Number:3
Record Number:CaltechAUTHORS:20151202-095604264
Persistent URL:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:62536
Deposited By: Tony Diaz
Deposited On:02 Dec 2015 22:58
Last Modified:19 Nov 2019 01:00

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