Spectral similarity of unbound asteroid pairs

Infrared (IR) spectroscopy between 0.8 and 2.5 μ has been obtained for both components of three unbound asteroid pairs, using theNASA Infrared Telescope Facility with the SpeX instrument. Pair primary (2110) Moore-Sitterly is classified as an S-type following the Bus-DeMeo taxonomy; the classification for secondary (44612) 1999 RP27 is ambiguous: S/Sq/Q/K/Ltype. Primary (10484) Hecht and secondary (44645) 1999 RC118 are classified as V-types. IR spectra for Moore-Sitterly and Hecht are each linked with available visual photometry. The classifications for primary (88604) 2001 QH293 and (60546) 2000 EE85 are ambiguous: S/Sq/Q/K/L-type. Subtle spectral differences between them suggest that the primary may have more weathered material on its surface. Dynamical integrations have constrained the ages of formation: 2110-44612 > 782 kyr; 10484-44645 = 348 (+823,-225) kyr; 88604-60546 = 925 (+842,-754) kyr. The spectral similarity of seven complete pairs is ranked in comparison with nearby background asteroids. Two pairs, 17198-229056 and 19289-278067, have significantly different spectra between the components, compared to the similarity of spectra in the background population. The other pairs are closer than typical, supporting an interpretation of each pair's formation from a common parent body. © 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society

Physical characterization of low delta-V asteroid (175706) 1996 FG3

Asteroid (175706) 1996 FG3 is a binary asteroid and the baseline target for the proposed MarcoPolo-R sample return mission. We present thermal-infrared photometry obtained with the European Southern Observatory (ESO) Very Large Telescope using the VISIR instrument, together with optical photometry obtained with the ESO New Technology Telescope using the EFOSC2 instrument. An absolute visual magnitude HV= 17.833 ± 0.024 and phase parameter G=-0.041 ± 0.005 are derived. The near-Earth asteroid thermal model has been fitted to the measured fluxes to derive a geometric visual albedo ?v= 0.046 p± 0.014, effective diameter at the observed aspect Deff= 1.68 ± 0.25 km and beaming parameter ? = 1.15 for phase angle ?±= 117. The advanced thermophysical model (ATPM) has been fitted to the measured fluxes to derive a more accurate effective diameter Deff= 1.71 ± 0.07km and albedo ?v= 0.044 ± 0.004. Based on the ATPM results, assuming the same albedo for primary and secondary, we derive a primary mean spherical diameter D?= 1.69+0.18 - 0.12km, secondary diameter Ds= 0.51 ± 0.03 km and a secondary orbital semimajor axis a= 2.8+1.7 -0.7km. A low surface thermal inertia ?= 120 ± 50Jm-2s-1/2K-1 was also derived, suggesting a dusty surface and raising questions as to the binary formation mechanism of this asteroid. These physical properties are used to predict a Yarkovsky drift in semimajor axis of -60+31 -45myr-1. © 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS