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Binary asteroid (31) Euphrosyne: ice-rich and nearly spherical

Yang, B. and Hanuš, J. and Carry, B. and Vernazza, P. and Brož, M. and Vachier, F. and Rambaux, N. and Marsset, M. and Chrenko, O. and Ševeček, P. and Viikinkoski, M. and Jehin, E. and Ferrais, M. and Podlewska-Gaca, E. and Drouard, A. and Marchis, F. and Birlan, M. and Benkhaldoun, Z. and Berthier, J. and Bartczak, P. and Dumas, C. and Dudziński, G. and Ďurech, J. and Castillo-Rogez, J. and Cipriani, F. and Colas, F. and Fetick, R. and Fusco, T. and Grice, J. and Jorda, L. and Kaasalainen, M. and Kryszczynska, A. and Lamy, P. and Marciniak, A. and Michalowski, T. and Michel, P. and Pajuelo, M. and Santana-Ros, T. and Tanga, P. and Vigan, A. and Witasse, O. (2020) Binary asteroid (31) Euphrosyne: ice-rich and nearly spherical. Astronomy and Astrophysics, 641 . Art. No. A80. ISSN 0004-6361. doi:10.1051/0004-6361/202038372.

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Aims. 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. Methods. 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. Results. We obtained disk-resolved images of Euphrosyne using SPHERE/ZIMPOL at the ESO 8.2 m 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. Conclusions. 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 ± 6 km, 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 ± 242 kg 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.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Hanuš, J.0000-0002-2934-3723
Carry, B.0000-0001-5242-3089
Jehin, E.0000-0001-8923-488X
Marchis, F.0000-0001-7016-7277
Fetick, R.0000-0002-1329-7603
Vigan, A.0000-0002-5902-7828
Additional Information:© ESO 2020. Received 7 May 2020 / Accepted 15 July 2020. This work has been supported by the Czech Science Foundation through grant 18-09470S (J. Hanuš, O. Chrenko, P. Ševeček) and by the Charles University Research program No. UNCE/SCI/023. M.B. was supported by the Czech Science Foundation grant 18-04514J. Computational resources were supplied by the Ministry of Education, Youth and Sports of the Czech Republic under the projects CESNET (LM2015042) and IT4Innovations National Supercomputing Centre (LM2015070). P. Vernazza, A. Drouard, M. Ferrais and B. Carry were supported by CNRS/INSU/PNP. M.M. was supported by the National Aeronautics and Space Administration under grant No. 80NSSC18K0849 issued through the Planetary Astronomy Program. The work of TSR was carried out through grant APOSTD/2019/046 by Generalitat Valenciana (Spain). This work was supported by the MINECO (Spanish Ministry of Economy) through grant RTI2018-095076-B-C21 (MINECO/FEDER, UE). The research leading to these results has received funding from the ARC grant for Concerted Research Actions, financed by the Wallonia-Brussels Federation. TRAPPIST is a project funded by the Belgian Fonds (National) de la Recherche Scientifique (F.R.S.-FNRS) under grant FRFC 2.5.594.09.F. TRAPPIST-North is a project funded by the Université de Liège, and performed in collaboration with Cadi Ayyad University of Marrakesh. E. Jehin is a FNRS Senior Research Associate.
Group:Thirty Meter Telescope
Funding AgencyGrant Number
Czech Science Foundation18-09470S
Charles UniversityUNCE/SCI/023
Czech Science Foundation18-04514J
Ministry of Education, Youth and Sports (Czech Republic)LM2015042
Ministry of Education, Youth and Sports (Czech Republic)LM2015070
Centre National de la Recherche Scientifique (CNRS)UNSPECIFIED
Institut national des sciences de l'Univers (INSU)UNSPECIFIED
Programme National de Planetologie (PNP)UNSPECIFIED
Generalitat ValencianaAPOSTD/2019/046
Ministerio de Economía, Industria y Competitividad (MINECO)RTI2018-095076-B-C21
Fondo Europeo de Desarrollo Regional (FEDER)UNSPECIFIED
Wallonia-Brussels FederationUNSPECIFIED
Fonds de la Recherche Scientifique (FNRS)FRFC 2.5.594.09.F
Université de LiègeUNSPECIFIED
Subject Keywords:techniques: high angular resolution / methods: observational / minor planets, asteroids: individual: (31) Euphrosyne / minor planets, asteroids: general
Record Number:CaltechAUTHORS:20200911-133141097
Persistent URL:
Official Citation:Binary asteroid (31) Euphrosyne: ice-rich and nearly spherical B. Yang, J. Hanuš, B. Carry, P. Vernazza, M. Brož, F. Vachier, N. Rambaux, M. Marsset, O. Chrenko, P. Ševeček, M. Viikinkoski, E. Jehin, M. Ferrais, E. Podlewska-Gaca, A. Drouard, F. Marchis, M. Birlan, Z. Benkhaldoun, J. Berthier, P. Bartczak, C. Dumas, G. Dudziński, J. Ďurech, J. Castillo-Rogez, F. Cipriani, F. Colas, R. Fetick, T. Fusco, J. Grice, L. Jorda, M. Kaasalainen, A. Kryszczynska, P. Lamy, A. Marciniak, T. Michalowski, P. Michel, M. Pajuelo, T. Santana-Ros, P. Tanga, A. Vigan and O. Witasse A&A, 641 (2020) A80 DOI:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:105366
Deposited By: George Porter
Deposited On:11 Sep 2020 21:38
Last Modified:16 Nov 2021 18:42

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