J/A+A/653/A57 (216) Kleopatra images (Marchis+, 2021)
(216) Kleopatra, a low density critically rotating M-type asteroid.
Marchis F., Jorda L., Vernazza P., Broz M., Hanus J., Ferrais M.,
Vachier F., Rambaux N., Marsset M., Viikinkoski M., Jehin E., Benseguane S.,
Podlewska-Gaca E., Carry B., Drouard A., Fauvaud S., Birlan M., Berthier J.,
Bartczak P., Dumas C., Dudzinski G., Durech J., Castillo-Rogez J.,
Cipriani F., Colas F., Fetick R., Fusco T., Grice J., Kryszczynska A.,
Lamy P., Marciniak A., Michalowski T., Michel P., Pajuelo M.,
Santana-Ros T., Tanga P., Vigan A., Witasse O., Yang B.
<Astron. Astrophys. 653, A57 (2021)>
=2021A&A...653A..57M 2021A&A...653A..57M (SIMBAD/NED BibCode)
ADC_Keywords: Solar system ; Minor planets
Keywords: techniques: high angular resolution -
minor planets: asteroids: individual: 216 Kleopatra
Abstract:
The recent estimates of the 3D shape of the M/Xe-type triple asteroid
system (216) Kleopatra indicated a density of ∼5g/cm3,
which is by far the highest for a small Solar System body. Such a high
density implies a high metal content as well as a low porosity which
is not easy to reconcile with its peculiar "dumbbell" shape.
Given the unprecedented angular resolution of the VLT/SPHERE/ZIMPOL
camera, here, we aim to constrain the mass (via the characterization
of the orbits of the moons) and the shape of (216) Kleopatra with high
accuracy, hence its density. We combined our new VLT/SPHERE
observations of (216) Kleopatra recorded during two apparitions in
2017 and 2018 with archival data from the W.M. Keck Observatory, as
well as lightcurve, occultation, and delay-Doppler images, to derive a
model of its 3D shape using two different algorithms (ADAM, MPCD).
Furthermore, an N-body dynamical model allowed us to retrieve the
orbital elements of the two moons as explained in the accompanying
paper.
The shape of (216) Kleopatra is very close to an equilibrium dumbbell
figure with two lobes and a thick neck. Its volume equivalent diameter
(118.75±1.40)km and mass (2.97±0.32)*1018kg (i.e., 56% lower
than previously reported) imply a bulk density of
(3.38±0.50)g/cm3. Such a low density for a supposedly metal-rich
body indicates a substantial porosity within the primary. This porous
structure along with its near equilibrium shape is compatible with a
formation scenario including a giant impact followed by
reaccumulation.
(216) Kleopatra's current rotation period and dumbbell shape imply
that it is in a critically rotating state. The low effective gravity
along the equator of the body, together with the equatorial orbits of
the moons and possibly rubble-pile structure, opens the possibility
that the moons formed via mass shedding.
Description:
Deconvolved direct imaging observations of Kleopatra using the MISTRAL
algorithm and a generated PSF.
Those fits files are direct images of (216) Kleopatra system. The
reduced images were further deconvolved with the Mistral algorithm
(Fusco et al., 2003, in Proc. SPIE, Vol. 4839, Adaptive Optical System
Technologies II, ed. P. L. Wizinowich & D. Bonaccini, 1065-1075),
using a parametric point-spread function (Fetick et al.,
2019A&A...623A...6F 2019A&A...623A...6F, Cat. J/A+A/623/A6).
object.dat :
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Planet Name H Diam e i a
mag km deg AU
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216 Kleopatra 7.15 135.1 0.25126552 13.116286 2.79243307
----------------------------------------------------------------------
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 175 11 List of fits images
fits/* . 11 Individual fits images
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
20- 26 F7.5 arcsec/pix scale Scale of the image
28- 30 I3 --- Nx Number of pixels along X-axis
32- 34 I3 --- Ny Number of pixels along Y-axis
36- 58 A23 "datime" Obs.date Observation date
60- 62 I3 Kibyte size Size of FITS file
64-130 A67 --- FileName Name of FITS file, in subdirectory fits
133-175 A43 --- Title Title of the FITS file
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Acknowledgements:
Franck Marchis, fmarchis(at)seti.org
(End) Patricia Vannier [CDS] 23-Aug-2021