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Thermophysical Modeling of New NEOWISE data on 2009 FD

Presentation #306.21 in the session “Asteroids, the Moon, and Meteorites”.

Published onOct 03, 2021
Thermophysical Modeling of New NEOWISE data on 2009 FD

The Apollo asteroid 410777 (2009 FD) with a very small MOID of 0.002 AU was seen by NEOWISE in 2010 while quite close to the Earth, which led to a large phase angle since WISE scans near 90 degree elongation from the Sun. In 2014 & 2015 it was reobserved by NEOWISE, again at close ranges and high phase angles. In 2019 & 2020 NEOWISEobserved 2009 FD again but at longer ranges and smaller phase angles. These 5 epochs give useful SNRs in the 4.6 micron band, and a thermophysical model assuming a spherical shape gives a reasonably good fit to all the infrared data with a rotation pole at (RA,Dec)=(312,51)±20 degrees (prograde), a diameter of 199+5-8 meters, and a dimensionless thermal inertia of Theta=3.3+8%-14%. With the optical H magnitude of 22.1 and a rotation period of 4.0 hours, the model gives an albedo of 5.2% and a thermal inertia of 540 in MKS units. This 199 m diameter is consistent with the high end of the equivalent area of the radar measured binary with component diameters of 120-180 and 60-120 m. We will discuss how the high phase angle, the high thermal inertia, and the lack of data covering the IR peak created problems for the NEATM.

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