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ATEL # 2984; M. Hicks (JPL/Caltech), H. Rhoades (JPL/Caltech)
on 29 Oct 2010; 17:25 UT
Password Certification: Michael D. Hicks (Michael.Hicks@jpl.nasa.gov)
Subjects: Optical, Asteroids, Planets, Planets (minor), Solar System Objects
The near-Earth asteroid 2010 TD54 was discovered by the Catalina Sky Survey on Oct 09.33 2010 (MPEC 2010-T65) at a distance of 0.031 AU from the Earth. Astrometric observations over the subsequent two days confirmed that the extremely small (D~5m) object would pass within 0.00035 AU of the Earth on Oct 12.55 2010.
We obtained 2.9 hours of Bessel BVRI photometry of 2010 TD54 at the JPL Table Mountain 0.6-m telescope (TMO) near Wrightwood, California on Oct 12 2010. Table 1 lists the observational circumstances. Figure 1 shows our observed photometry, with a monotonic increase in brightness caused by the rapidly decreasing geocentric distance. Our data can not be used to constrain solar phase behavior.
The object's averaged colors (B-R=1.284+/-0.045 mag; V-R=0.461+/-0.030 mag; R-I=0.344+/-0.022 mag) are compatible with an S-type spectral classification (Bus Taxonomy)/S-type (Tholen Taxonomy), an association obtained through a comparison of our colors with the 1341 asteroid spectra in the SMASS II database (Bus & Binzel 2002) [Figure 2 and Table 2]. Assuming a a solar phase parameter g=0.15, our photometry yields an absolute magnitude H_V = 28.751 +/- 0.030 mag, implying an effective diameter of between 3 m and 6 m for a plausible range of albedo.
After converting our photometry from magnitude to flux units, we performed a rotational period search using standard Fourier techniques. Figure 3 plots chi-squared Fourier model misfit as a function of assumed rotation period. Assuming a double-peaked lightcurve, we found a best-fit synodic period P_syn = 42.00+/-0.03 sec, as shown in Figure 4. We stress that this rotation period is preliminary but if verified this would make 2010 TD54 one of, if not the fastest, rotating natural body known in the solar system, comparable to to 42.67+/-0.04 sec period for 2008 HJ as measured by R. Miles (CBET 1382).
Copyright 2010 California Institute of Technology. Government sponsorship acknowledged.
Table 1: Observational Circumstances. UT Time r (AU) delta phase V [AU] [AU] [deg] [mag] Start: 2010 10 12.14 1.0010 0.0030 12.4 16.9 Stop: 2010 10 12.27 0.9999 0.0018 15.8 15.9
Table 2: Best-fit SMASS II spectral analogs. TAXONOMIC CLASS MISFIT OBJECT NAME (THOLEN) (BUS) 0.507 1948 Kampala S 0.573 1640 Nemo S 0.630 40 Harmonia S S 0.688 519 Sylvania S S 0.757 1635 Bohrmann S