Radar observations of Asteroids 64 Angelina and 69 Hesperia

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• 作者：Michael K.  ; Shepard^a ;   ; ^{mshepard@bloomu.edu} ; Alan W.  ; Harris^b ; Patrick A.  ; Taylor^c ; Beth Ellen  ; Clark^d ; Maureen  ; Ockert-Bell^d ; Michael C.  ; Nolan^c ; Ellen S.  ; Howell^c ; Christopher  ; Magri^e ; Jon D.  ; Giorgini^f ; Lance A.M.  ; Benner^f
• 关键词：Asteroids ; Asteroids ; Composition ; Radar observations
• 刊名：Icarus
• 出版年：2011
• 出版时间：October 2011
• 年：2011
• 卷：215
• 期：2
• 页码：547-551
• 全文大小：472 K

文摘

We report new radar observations of E-class Asteroid 64 Angelina and M-class Asteroid 69 Hesperia obtained with the Arecibo Observatory S-band radar (2480 MHz, 12.6 cm). Our measurements of Angelina¡¯s radar bandwidth are consistent with reported diameters and poles. We find Angelina¡¯s circular polarization ratio to be 0.8 ¡À 0.1, tied with 434 Hungaria for the highest value observed for main-belt asteroids and consistent with the high values observed for all E-class asteroids (Benner, L.A.M., Ostro, S.J., Magri, C., Nolan, M.C., Howell, E.S., Giorgini, J.D., Jurgens, R.F., Margot, J.L., Taylor, P.A., Busch, M.W., Shepard, M.K. [2008]. Icarus 198, 294?04; Shepard, M.K., Kressler, K.M., Clark, B.E., Ockert-Bell, M.E., Nolan, M.C., Howell, E.S., Magri, C., Giorgini, J.D., Benner, L.A.M., Ostro, S.J. [2008b]. Icarus 195, 220?25). Our radar observations of 69 Hesperia, combined with lightcurve-based shape models, lead to a diameter estimate, mlns="""">D_{mlns="""">eff} = 110 ¡À 15 km, approximately 20 % smaller than the reported IRAS value. We estimate Hesperia to have a radar albedo of , consistent with a high-metal content. We therefore add 69 Hesperia to the Mm-class (high metal M) (Shepard, M.K., Clark, B.E., Ockert-Bell, M., Nolan, M.C., Howell, E.S., Magri, C., Giorgini, J.D., Benner, L.A.M., Ostro, S.J., Harris, A.W., Warner, B.D., Stephens, R.D., Mueller, M. [2010]. Icarus 208, 221?37), bringing the total number of Mm-class objects to eight; this is 40 % of all M-class asteroids observed by radar to date.