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Broad-band Photometry of the Binary Potentially Hazardous Asteroid 2003 YT1.

ATEL # 2289; M. Hicks (JPL/Caltech); J. Somers (Moorpark College); T. Barajas (LACC); J. Foster, A. McAuley, J. Shitanishi (CSULA)
on 10 Nov 2009; 20:42 UT
Password Certification: Michael D. Hicks (

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

The near-Earth asteroid 2003 YT1 was discovered by the Catalina Sky Survey on December 18 2003 (MPEC 2003-Y30). With an Absolute Magnitude H=16.2 and a Minimum Orbit Intersection Distance MOID=0.004 AU (~1.5 lunar distances) the object is considered a Potentially Hazardous Asteroid (PHA). During the discovery apparition delay-doppler radar imaging at Arecibo and optical photometric observations at the Modra and Ondrejov Observatories independently confirmed 2003 YT1 to be a binary asteroid (IAUC 8336). Spectral data from 0.7-2.5 micron obtained at the IRTF (Abell et al. 2004) indicated a composition dominated by orthopyroxene with very low olivine content suggesting 2003 YT1 likely represents a collisional fragment ejected from a highly differentiated parent body, perhaps asteroid 4 Vesta.

2003 YT1 is scheduled for new radar observations at Arecibo in November 2009 and in anticipation we obtained Bessel BVRI colors over the course of four partial nights at the JPL Table Mountain Observatory (TMO) 0.6-m telescope (Figure 1 and Table 1) Our averaged colors (B-R = 1.405+/-0.029 mag; V-R = 0.498+/-0.026 mag; R-I = 0.124+/-0.029 mag) were compared with the spectra of 1341 asteroids in the SMASS II database (Bus & Binzel 2002). As shown in Figure 2, we found the colors of 2003 YT1 more compatible with the R-type asteroids 1904 Massevitch and 349 Dembowska (Bus Taxonomy) than to a V-type classification, although an Sr-type classification is also allowed by our photometry. We encourage observers in the coming weeks to obtain optical and/or near-IR spectroscopy in order to explore the potential link of 2003 YT1 with asteroid 4 Vesta and the basaltic achondrite meteorites.

Copyright 2009. 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.

Table 1: TMO Observational Summary.

UT Date r(AU) d(AU) Phase(deg) R_avg(mag) Num. Exp. Observers
Oct 10 1.090 0.289 64.2 15.37 34 Barajas
Oct 11 1.085 0.276 64.6 15.28 38 Foster
Oct 17 1.056 0.202 67.7 14.79 31 Somers, Hicks
Oct 22 1.031 0.150 72.2 14.10 53 McAuley, Shitanishi

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