TY - JOUR
T1 - Radar observations of E-class Asteroids 44 Nysa and 434 Hungaria
AU - Shepard, Michael K.
AU - Kressler, Karelyn M.
AU - Clark, Beth Ellen
AU - Ockert-Bell, Maureen E.
AU - Nolan, Michael C.
AU - Howell, Ellen S.
AU - Magri, Christopher
AU - Giorgini, Jon D.
AU - Benner, Lance A.M.
AU - Ostro, Steven J.
N1 - Funding Information:
M.K.S. and K.M.K. gratefully acknowledge support from a NSF REU grant, AST-0605903. B.E.C. and M.E.O. were supported by NSF grant AST-0606704. C.M. was partially supported by NSF grant AST-0205975. The Arecibo Observatory is part of the National Astronomy and Ionosphere Center, which is operated by Cornell University under a cooperative agreement with the National Science Foundation. We thank the technical staff at the observatory for help with observations. Some of this work was performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. This material is based in part upon work supported by the National Aeronautics and Space Administration (NASA) under the Science Mission Directorate Research and Analysis Programs.
PY - 2008/5
Y1 - 2008/5
N2 - We observed the E-class main-belt Asteroids (MBAs) 44 Nysa and 434 Hungaria with Arecibo Observatory's S-band (12.6 cm) radar. Both asteroids exhibit polarization ratios higher than those measured for any other MBA: Nysa, μc = 0.50 ± 0.02 and Hungaria, μc = 0.8 ± 0.1. This is consistent with the high polarization ratios measured for every E-class near-Earth asteroid (NEA) observed by Benner et al. [Benner, L.A.M., and 10 collegues, 2008. Icarus, submitted for publication] and suggests a common cause. Our estimates of radar albedo are 0.19 ± 0.06 for Nysa and 0.22 ± 0.06 for Hungaria. These values are higher than those of most MBAs and, when combined with their high polarization ratios, suggest that the surface bulk density of both asteroids is high. We model Nysa as an ellipsoid of dimension 113 × 67 × 65 km (± 15 %) giving an effective diameter Deff = 79 ± 10 km, consistent with previous estimates. The echo waveforms are not consistent with a contact binary as suggested by Kaasalainen et al. [Kaasalainen, M., Torppa, J., Piironen, J., 2002. Astron. Astrophys. 383, L19-L22]. We place a constraint on Hungaria's maximum diameter, Dmax ≥ 11 km consistent with previous size estimates.
AB - We observed the E-class main-belt Asteroids (MBAs) 44 Nysa and 434 Hungaria with Arecibo Observatory's S-band (12.6 cm) radar. Both asteroids exhibit polarization ratios higher than those measured for any other MBA: Nysa, μc = 0.50 ± 0.02 and Hungaria, μc = 0.8 ± 0.1. This is consistent with the high polarization ratios measured for every E-class near-Earth asteroid (NEA) observed by Benner et al. [Benner, L.A.M., and 10 collegues, 2008. Icarus, submitted for publication] and suggests a common cause. Our estimates of radar albedo are 0.19 ± 0.06 for Nysa and 0.22 ± 0.06 for Hungaria. These values are higher than those of most MBAs and, when combined with their high polarization ratios, suggest that the surface bulk density of both asteroids is high. We model Nysa as an ellipsoid of dimension 113 × 67 × 65 km (± 15 %) giving an effective diameter Deff = 79 ± 10 km, consistent with previous estimates. The echo waveforms are not consistent with a contact binary as suggested by Kaasalainen et al. [Kaasalainen, M., Torppa, J., Piironen, J., 2002. Astron. Astrophys. 383, L19-L22]. We place a constraint on Hungaria's maximum diameter, Dmax ≥ 11 km consistent with previous size estimates.
KW - Asteroids
KW - Radar observations
KW - composition
KW - surfaces
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U2 - 10.1016/j.icarus.2007.12.018
DO - 10.1016/j.icarus.2007.12.018
M3 - Article
AN - SCOPUS:42149194526
SN - 0019-1035
VL - 195
SP - 220
EP - 225
JO - Icarus
JF - Icarus
IS - 1
ER -