11 research outputs found
65 Cybele in the thermal infrared: Multiple observations and thermophysical analysis
We investigated the physical and thermal properties of 65 Cybele}, one of the
largest main-belt asteroids. Based on published and recently obtained thermal
infrared observations, including ISO measurements, we derived through
thermophysical modelling (TPM) a size of 302x290x232 km (+/- 4 %) and an
geometric visible albedo of 0.050+/-0.005. Our model of a regolith covered
surface with low thermal inertia and "default" roughness describes the
wavelengths and phase angle dependent thermal aspects very well. Before/after
opposition effect and beaming behaviour can be explained in that way. We found
a constant emissivity of 0.9 at wavelengths up to about 100 micron and lower
values towards the submillimetre range, indicating a grain size distribution
dominated by 200 micron particle sizes. The spectroscopic analysis revealed an
emissivity increase between 8.0 and 9.5 micron. We compared this emissivity
behaviour with the Christiansen features of carbonaceous chondrite meteorites,
but a conclusive identification was not possible. A comparison between the
Standard Thermal Model (STM) and the applied TPM clearly demonstrates the
limitations and problems of the STM for the analysis of multi-epoch and
-wavelengths observations. While the TPM produced a unique diameter/albedo
solution, the calculated STM values varied by +/-30 % and showed clear trends
with wavelength and phase angle. Cybele can be considered as a nice textbook
case for the thermophysical analysis of combined optical and thermal infrared
observations.Comment: 11 pages, 8 figures, accepted for publication by A&
Mechanical engineer handbook ( in two volumes power volume)/ J. Kenneth Salibury (editor)
xi, hal tak beraturan.: ind.; 22 c
Mechanical engineer handbook ( in two volumes power volume)/ J. Kenneth Salibury (editor)
xi, hal tak beraturan.: ind.; 22 c