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Broadband Photometry of the Near-Earth Asteroid 66146 (1998 TU3)

ATEL # 2833; M. Hicks (JPL/Caltech), T. Truong (CSULA)
on 7 Sep 2010; 22:55 UT
Password Certification: Michael D. Hicks (Michael.Hicks@jpl.nasa.gov)

Subjects: Optical, Asteroids, Planets, Planets (minor), Solar System Objects

The near-Earth asteroid 66146 (1998 TU3) was discovered on 1998 October 13 by the LINEAR survey (MPEC 1998-U03). We obtained six nights of Bessel BVRI observations at the JPL Table Mountain Observatory (TMO) 0.6-m telescope with observational circumstances are summarized in Table 1. All BVI data points illustrated in Figure 1 were plotted after offsetting relative to R by the nightly colors as listed in Table 2.

The object's mean colors (B-R=1.238+/-0.011 mag; V-R=0.440+/-0.008 mag; R-I=0.275+/-0.010 mag) were found most compatible with an Sk-type (Bus Taxonomy)/S-type (Tholen Taxonomy) classification. This association was obtained through a comparison of our colors with the 1341 asteroid spectra in the SMASS II database (Bus & Binzel 2002) [Figure 2 and Table 3]. Our classification differs significantly from the Q-type taxonomy reported by Whitely (2002).

Assuming a solar phase parameter g=0.15 we found a best-fit rotational period P_syn=2.378+/-0.001 hr, near the rotational break-up speed and in excellent agreement with the 2.3779+/-0.0004 period determined by Richards et al.(2007). The dispersion in the phased lightcurve [Figure 3] suggests that 1998 TU3 may be a binary system, with variations in observed flux caused by an unresolved, tidally locked secondary companion. Fitting a 2-period model as described by Pravec et al. (2000), we found that our photometry agrees well with a binary model (P_1=2.378+/-0.01 hr, P_2=28.28+/-0.05 hr), though the lightcurve amplitude of the secondary component was not well constrained [Figure 4].

1998 TU3's exceptional apparitions in 2010 and 2012 implies that it may be a good candidate for shape/pole modeling via lightcurve inversion, especially if photometry can be obtained from both northern and southern hemispheres. We welcome any potential collaborations.

Copyright 2010. All rights reserved. The research described in this telegram was carried out at the Jet Propulsion Laboratory, under a contract with the National Aeronautics and Space Administration. The student participation was supported by the National Science Foundation under REU grant 0852088 to Cal State LA.

   Table 1: Observational Circumstances.      UT Time        r (AU)  delta  phase   V   Filters  Observers                   [AU]    [AU]  [deg] [mag]   2010 08 06.48  1.050   0.449  73.0  15.5   BVRI    Truong   2010 08 07.47  1.055   0.446  72.5  15.4   BVRI    Hicks   2010 08 08.47  1.060   0.443  71.9  15.4     R     Truong/Hicks   2010 08 10.46  1.069   0.436  70.8  15.4   BVRI    Truong   2010 08 12.48  1.078   0.429  69.7  15.3   BVRI    Truong   2010 08 13.48  1.083   0.426  69.2  15.3   BVRI    Truong   


   Table 2:  Relative Colors.      UT Date          B-R            V-R            R-I                   [mag]          [mag]          [mag]   2010 08 06  1.241+/-0.027  0.419+/-0.013  0.292+/-0.012   2010 08 07  1.239+/-0.016  0.438+/-0.012  0.279+/-0.014   2010 08 10  1.212+/-0.039  0.467+/-0.013  0.243+/-0.016   2010 08 12  1.257+/-0.026  0.467+/-0.026  0.269+/-0.025   2010 08 13  1.231+/-0.034  0.426+/-0.025  0.262+/-0.012   mean:       1.238+/-0.011  0.440+/-0.008  0.275+/-0.010   


   Table 3:  Best-fit SMASS II spectral analogs.                                TAXONOMIC CLASS   MISFIT  OBJECT NAME        (THOLEN) (BUS)   2.192     3 Juno              S       Sk   2.412  2748 Patrick Gene              S   2.632   485 Genua                     S   2.688  5407 1992 AX                   Sk   2.764   179 Klytaemnestra     S       Sk   2.833   196 Philomela         S       S   


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