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Broadband photometry of 2002 VE68, a quasi-moon of Venus.

ATel #3073; M. Hicks (JPL/Caltech), D. Mayes (JPL/Caltech), T. Barajas (LACC)
on 8 Dec 2010; 20:19 UT
Credential Certification: Michael D. Hicks (Michael.Hicks@jpl.nasa.gov)

Subjects: Optical, Asteroid, Planet (minor), Solar System Object

The Near-Earth Object (NEO) 2002 VE68 was discovered by the LONEOS Survey on Nov 11 2002 (MPEC 2002-V52). With a semi-major axis a=0.723 AU, 2002 VE68 is in a 1:1 mean motion resonance with Venus and can be considered a quasi-satellite of the planet. Orbital integrations by Mikkola et al. (2004) suggest that 2002 VE68 was likely an NEO injected into its current orbit by a close Earth encounter approximately 7000 years ago and will remain a Venusian quasi-satellite for another 500 years. This object has been designated a Potentially Hazardous Asteroid by the Minor Planet Center.

We took advantage of the object's 2010 apparition to collect rotationally resolved Bessel BVRI photometry over the course of three nights (Nov 10/12/13 2010) using the JPL Table Mountain 0.6-m telescope (TMO) near Wrightwood, California, as shown in Figures 1-3 [1] [2] [3]. Table 1 lists the observational circumstances, with heliocentric, geocentric, solar phase angle and expected V magnitude. All BVI data points illustrated in Figure 1-3 are plotted after offsetting relative to R by the nightly colors listed in Table 2.

The object's mean colors (B-R=1.106+/-0.019 mag; V-R=0.419+/-0.021 mag; R-I=0.348+/-0.014 mag) are most compatible with an X-type spectral classification (Bus Taxonomy), as shown in Figure 4 and Table 3. The slight reflectance dip at 0.55 micron is consistent with the deep 0.50 micron feature observed in the spectrum of the E-type asteroid 2867 Steins (Weissman et al. 2008). The spectral resolution that our BVRI photometry affords is often insufficient to resolve the E-M-P sub-classes within the X-spectral complex (Tholen Taxonomy).

After converting the photometry from magnitude to flux units, we found a best-fit synodic period P_syn = 13.50+/-0.01 hr [Figure 5]. Our photometry yields an absolute magnitude H_v=20.59+/-0.02 mag, implying an effective diameter D~200m (rho=0.25). The lightcurve amplitude of 2002 VE68 (~0.9 mag) suggests that it may be a contact binary.

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.  
  
                               Solar  Exp.    Num.  
   UT DATE       r     delta   Phase   V      Exp.   OBSERVER(S)  
                [AU]    [AU]   [deg]  [mag]  
2010 11 10.33  1.021   0.039   38.1   14.9     63    Mayes  
2010 11 12.22  1.021   0.043   44.3   15.3    121    Mayes  
2010 11 13.32  1.020   0.047   48.1   15.6     35    Barajas  
  
  
Table 2:  Relative colors.  
  
UT Date          B-R            V-R            R-I  
                [mag]          [mag]          [mag]  
2010 11 10  1.112+/-0.014  0.432+/-0.022  0.338+/-0.013  
2010 11 12  1.094+/-0.018  0.404+/-0.028  0.347+/-0.013  
2010 11 13  1.107+/-0.020  0.422+/-0.012  0.367+/-0.013  
mean:       1.106+/-0.019  0.419+/-0.021  0.348+/-0.014  
  
  
Table 3:  Best-fit SMASS II spectral analogs.  
  
                         TAXONOMIC CLASS  
MISFIT    OBJECT NAME    (THOLEN)  (BUS)  
1.609  1114 Lorraine                 Xc  
1.797  5294 Onnetoh                  X  
1.846   796 Sarita           XD      X  
1.848   107 Camilla          C       X  
1.867  3686 Antoku                   X