15 research outputs found
Volumes and bulk densities of forty asteroids from ADAM shape modeling
Get PDFDisk-integrated photometric data of asteroids do not contain accurate
information on shape details or size scale. Additional data such as
disk-resolved images or stellar occultation measurements further constrain
asteroid shapes and allow size estimates. We aim to use all available
disk-resolved images of about forty asteroids obtained by the Near-InfraRed
Camera (Nirc2) mounted on the W.M. Keck II telescope together with the
disk-integrated photometry and stellar occultation measurements to determine
their volumes. We can then use the volume, in combination with the known mass,
to derive the bulk density. We download and process all asteroid disk-resolved
images obtained by the Nirc2 that are available in the Keck Observatory Archive
(KOA). We combine optical disk-integrated data and stellar occultation profiles
with the disk-resolved images and use the All-Data Asteroid Modeling (ADAM)
algorithm for the shape and size modeling. Our approach provides constraints on
the expected uncertainty in the volume and size as well. We present shape
models and volume for 41 asteroids. For 35 asteroids, the knowledge of their
mass estimates from the literature allowed us to derive their bulk densities.
We clearly see a trend of lower bulk densities for primitive objects
(C-complex) than for S-complex asteroids. The range of densities in the
X-complex is large, suggesting various compositions. Moreover, we identified a
few objects with rather peculiar bulk densities, which is likely a hint of
their poor mass estimates. Asteroid masses determined from the Gaia astrometric
observations should further refine most of the density estimates.Comment: Accepted for publication in A&
Combining asteroid models derived by lightcurve inversion with asteroidal occultation silhouettes
Full text linkAsteroid sizes can be directly measured by observing occultations of stars by
asteroids. When there are enough observations across the path of the shadow,
the asteroid's projected silhouette can be reconstructed. Asteroid shape models
derived from photometry by the lightcurve inversion method enable us to predict
the orientation of an asteroid for the time of occultation. By scaling the
shape model to fit the occultation chords, we can determine the asteroid size
with a relative accuracy of typically ~ 10%. We combine shape and spin state
models of 44 asteroids (14 of them are new or updated models) with the
available occultation data to derive asteroid effective diameters. In many
cases, occultations allow us to reject one of two possible pole solutions that
were derived from photometry. We show that by combining results obtained from
lightcurve inversion with occultation timings, we can obtain unique physical
models of asteroids.Comment: 33 pages, 45 figures, 4 tables, accepted for publication in Icaru
