J/A+A/641/A80 Asteroid (31) Euphrosyne R-band images (Yang+, 2020)
Binary asteroid (31) Euphrosyne: ice-rich and nearly spherical.
Yang B., Hanus J., Carry B., Vernazza P., Broz M., Vachier F., Rambaux N.,
Marsset M., Chrenko O., Sevecek P., Viikinkoski M., Jehin E., Ferrais M.,
Podlewska-Gaca E., Drouard A., Marchis F., Birlan M., Benkhaldoun Z.,
Berthier J., Bartczak P., Dumas C., Dudzinski G., Durech J.,
Castillo-Rogez J., Cipriani F., Colas F., Fetick R., Fusco T., Grice J.,
Jorda L., Kaasalainen M., Kryszczynska A., Lamy P., Marciniak A.,
Michalowski T., Michel P., Pajuelo M., Santana-Ros T., Tanga P., Vigan A.,
Witasse O.
<Astron. Astrophys. 641, A80 (2020)>
=2020A&A...641A..80Y 2020A&A...641A..80Y (SIMBAD/NED BibCode)
ADC_Keywords: Minor planets ; Photometry
Keywords: techniques: high angular resolution - methods: observational -
minor planets, asteroids: individual: (31) Euphrosyne -
minor planets, asteroids: general -
Abstract:
Asteroid (31) Euphrosyne is one of the biggest objects in the asteroid
main belt and it is also the largest member of its namesake family.
The Euphrosyne family occupies a highly inclined region in the outer
main belt and contains a remarkably large number of members, which is
interpreted as an outcome of a disruptive cratering event.The goals of
this adaptive-optics imaging study are threefold: to characterize the
shape of Euphrosyne, to constrain its density, and to search for the
large craters that may be associated with the family formation event.
We obtained disk-resolved images of Euphrosyne using SPHERE/ZIMPOL at
the ESO 8.2m VLT as part of our large program (ID: 199.C-0074, PI:
Vernazza). We reconstructed its 3D shape via the ADAM shape modeling
algorithm based on the SPHERE images and the available light curves of
this asteroid. We analyzed the dynamics of the satellite with the
\genoid meta-heuristic algorithm. Finally, we studied the shape of
Euphrosyne using hydrostatic equilibrium models. Our SPHERE
observations show that Euphrosyne has a nearly spherical shape with
the sphericity index of 0.9888 and its surface lacks large impact
craters. Euphrosyne's diameter is 268±6km, making it one of the top
ten largest main belt asteroids. We detected a satellite of Euphrosyne
- S/2019 (31) 1 - that is about 4 km across, on a circular orbit. The
mass determined from the orbit of the satellite together with the
volume computed from the shape model imply a density of
1665±242kg/m-3, suggesting that Euphrosyne probably contains a
large fraction of water ice in its interior. We find that the
spherical shape of Euphrosyne is a result of the reaccumulation
process following the impact, as in the case of (10)Hygiea. However,
our shape analysis reveals that, contrary to Hygiea, the axis ratios
of Euphrosyne significantly differ from those suggested by fluid
hydrostatic equilibrium following reaccumulation.
Description:
Euphrosyne was observed, between March and April 2019 (2019-03-15,
2019-03-20, 2019-03-25, 2019-03-27, 2019-04-10), using the Zurich
Imaging Polarimeter (ZIMPOL) of SPHERE in the direct imaging mode with
the narrow band filter (N_R filter; filter central wavelength=645.9nm,
width=56.7nm).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 171 5 List of fits files
fits/* . 5 Individual fits files
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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- 31 I4 --- Nx Number of pixels along X-axis
33- 36 I4 --- Ny Number of pixels along Y-axis
38- 60 A23 "datime" Obs.date Observation date
62- 65 I4 Kibyte size Size of FITS file
67-117 A51 --- FileName Name of FITS file, in subdirectory fits
119-171 A53 --- Title Title of the FITS file
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Acknowledgements:
Bin Yang, byang(at)eso.org
(End) Patricia Vannier [CDS] 01-Sep-2020