Astronomy and Astrophysics – Astronomy
Scientific paper
Oct 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010dps....42.5305s&link_type=abstract
American Astronomical Society, DPS meeting #42, #53.05; Bulletin of the American Astronomical Society, Vol. 42, p.1073
Astronomy and Astrophysics
Astronomy
Scientific paper
Using the S-band radar at Arecibo Observatory, we observed the E-class asteroid 64 Angelina and the M-class asteroid 69 Hesperia. We obtained a single run on Angelina on 31 Jan 2010 with a signal-to-noise (SNR) of 10. We find its circular polarization ratio (SC/OC) to be muc = 0.8 +/- 0.1, tied with 434 Hungaria for the highest value measured for any main-belt asteroid (Shepard et al. 195, 220-225, 2008). This is consistent with the high polarization ratios observed for the E-class asteroids in general (Benner et al. Icarus 198, 294-304, 2008). Our estimate of the echo's bandwidth is B = 35 +/- 5 Hz. This is inconsistent with a published diameter of 60 km (Morrison and Chapman, ApJ 204, 934-939, 1976) and published rotation pole (lambda/beta 138/+31 deg, uncertainties +/- 10 deg, Shevchenko et al. PSS 51, 525-532, 2003). Either the pole is significantly different, the diameter is smaller, or some combination of these. We obtained two runs on 69 Hesperia on 3 Feb 2010 with a total SNR of 24. We estimate a bandwidth of B = 440 +/- 40 Hz that is 75% of the expected value based on the published diameter (IRAS, 138 km) and pole direction (lambda/beta 73 / -45 deg, Torppa et al. Icarus 164, 346-383, 2003). We estimate a radar albedo of 0.4 for the first run, placing it in the high-metal M-class (Mm) class defined by Shepard et al. (Icarus, 208, 221-237, 2010). Acknowledgements: This work was funded by NSF grant AST-0908098 to MKS and AST-0908217 to BEC.
Benner Lance A. M.
Clark Beth Ellen
Giorgini Jon D.
Howell Ellen S.
Magri Christopher
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