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Title: ASTEROID LIGHT CURVES FROM THE PALOMAR TRANSIENT FACTORY SURVEY: ROTATION PERIODS AND PHASE FUNCTIONS FROM SPARSE PHOTOMETRY

Abstract

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 lessmore » dense than ∼2 g cm{sup −3}, while C types have a lower limit of between 1 and 2 g cm{sup −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.« less

Authors:
 [1]; ; ; ;  [2];  [3]; ;  [4]; ;  [5]; ; ;  [6]
  1. Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125 (United States)
  2. Institute of Astronomy, National Central University, Jhongli, Taiwan (China)
  3. Benoziyo Center for Astrophysics, Weizmann Institute of Science, Rehovot (Israel)
  4. Spitzer Science Center, California Institute of Technology, Pasadena, CA 91125 (United States)
  5. Infrared Processing and Analysis Center, California Institute of Technology, Pasadena, CA 91125 (United States)
  6. Division of Physics, Mathematics and Astronomy, California Institute of Technology, Pasadena, CA 91125 (United States)
Publication Date:
OSTI Identifier:
22520157
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astronomical Journal (Online); Journal Volume: 150; Journal Issue: 3; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ALBEDO; ASTEROIDS; COLOR; COMPARATIVE EVALUATIONS; DENSITY; DIAGRAMS; GRAVITATION; PHOTOMETRY; PLANETS; ROTATION; SPIN; STRESSES; TRANSIENTS; VISIBLE RADIATION

Citation Formats

Waszczak, Adam, Chang, Chan-Kao, Cheng, Yu-Chi, Ip, Wing-Huen, Kinoshita, Daisuke, Ofek, Eran O., Laher, Russ, Surace, Jason, Masci, Frank, Helou, George, Levitan, David, Prince, Thomas A., and Kulkarni, Shrinivas, E-mail: waszczak@caltech.edu. ASTEROID LIGHT CURVES FROM THE PALOMAR TRANSIENT FACTORY SURVEY: ROTATION PERIODS AND PHASE FUNCTIONS FROM SPARSE PHOTOMETRY. United States: N. p., 2015. Web. doi:10.1088/0004-6256/150/3/75.
Waszczak, Adam, Chang, Chan-Kao, Cheng, Yu-Chi, Ip, Wing-Huen, Kinoshita, Daisuke, Ofek, Eran O., Laher, Russ, Surace, Jason, Masci, Frank, Helou, George, Levitan, David, Prince, Thomas A., & Kulkarni, Shrinivas, E-mail: waszczak@caltech.edu. ASTEROID LIGHT CURVES FROM THE PALOMAR TRANSIENT FACTORY SURVEY: ROTATION PERIODS AND PHASE FUNCTIONS FROM SPARSE PHOTOMETRY. United States. doi:10.1088/0004-6256/150/3/75.
Waszczak, Adam, Chang, Chan-Kao, Cheng, Yu-Chi, Ip, Wing-Huen, Kinoshita, Daisuke, Ofek, Eran O., Laher, Russ, Surace, Jason, Masci, Frank, Helou, George, Levitan, David, Prince, Thomas A., and Kulkarni, Shrinivas, E-mail: waszczak@caltech.edu. Tue . "ASTEROID LIGHT CURVES FROM THE PALOMAR TRANSIENT FACTORY SURVEY: ROTATION PERIODS AND PHASE FUNCTIONS FROM SPARSE PHOTOMETRY". United States. doi:10.1088/0004-6256/150/3/75.
@article{osti_22520157,
title = {ASTEROID LIGHT CURVES FROM THE PALOMAR TRANSIENT FACTORY SURVEY: ROTATION PERIODS AND PHASE FUNCTIONS FROM SPARSE PHOTOMETRY},
author = {Waszczak, Adam and Chang, Chan-Kao and Cheng, Yu-Chi and Ip, Wing-Huen and Kinoshita, Daisuke and Ofek, Eran O. and Laher, Russ and Surace, Jason and Masci, Frank and Helou, George and Levitan, David and Prince, Thomas A. and Kulkarni, Shrinivas, E-mail: waszczak@caltech.edu},
abstractNote = {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{sup −3}, while C types have a lower limit of between 1 and 2 g cm{sup −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.},
doi = {10.1088/0004-6256/150/3/75},
journal = {Astronomical Journal (Online)},
number = 3,
volume = 150,
place = {United States},
year = {Tue Sep 15 00:00:00 EDT 2015},
month = {Tue Sep 15 00:00:00 EDT 2015}
}
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