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Homogeneous internal structure of CM-like asteroid (41) Daphne

Carry, B. and Vachier, F. and Berthier, J. and Marsset, M. and Vernazza, P. and Grice, J. and Merline, W. J. and Lagadec, E. and Fienga, A. and Conrad, A. and Podlewska-Gaca, E. and Santana-Ros, T. and Viikinkoski, M. and Hanuš, J. and Dumas, C. and Drummond, J. D. and Tamblyn, P. M. and Chapman, C. R. and Behrend, R. and Bernasconi, L. and Bartczak, P. and Benkhaldoun, Z. and Birlan, M. and Castillo-Rogez, J. and Cipriani, F. and Colas, F. and Drouard, A. and Ďurech, J. and Enke, B. L. and Fauvaud, S. and Ferrais, M. and Fetick, R. and Fusco, T. and Gillon, M. and Jehin, E. and Jorda, L. and Kaasalainen, M. and Keppler, M. and Kryszczynska, A. and Lamy, P. and Marchis, F. and Marciniak, A. and Michalowski, T. and Michel, P. and Pajuelo, M. and Tanga, P. and Vigan, A. and Warner, B. and Witasse, O. and Yang, B. and Zurlo, A. (2019) Homogeneous internal structure of CM-like asteroid (41) Daphne. Astronomy and Astrophysics, 623 . Art. No. A132. ISSN 0004-6361.

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Context. CM-like asteroids (Ch and Cgh classes) are a major population within the broader C-complex, encompassing about 10% of the mass of the main asteroid belt. Their internal structure has been predicted to be homogeneous, based on their compositional similarity as inferred from spectroscopy and numerical modeling of their early thermal evolution. Aims. Here we aim to test this hypothesis by deriving the density of the CM-like asteroid (41) Daphne from detailed modeling of its shape and the orbit of its small satellite. Methods. We observed Daphne and its satellite within our imaging survey with the Very Large Telescope extreme adaptive-optics SPHERE/ZIMPOL camera and complemented this data set with earlier Keck/NIRC2 and VLT/NACO observations. We analyzed the dynamics of the satellite with our Genoid meta-heuristic algorithm. Combining our high-angular resolution images with optical lightcurves and stellar occultations, we determine the spin period, orientation, and 3D shape, using our ADAM shape modeling algorithm. Results. The satellite orbits Daphne on an equatorial, quasi-circular, prograde orbit, like the satellites of many other large main-belt asteroids. The shape model of Daphne reveals several large flat areas that could be large impact craters. The mass determined from this orbit combined with the volume computed from the shape model implies a density for Daphne of 1.77 ± 0.26 g cm⁻³ (3 σ). This densityis consistent with a primordial CM-like homogeneous internal structure with some level of macroporosity (≈ 17%). Conclusions. Based on our analysis of the density of Daphne and 75 other Ch/Cgh-type asteroids gathered from the literature, we conclude that the primordial internal structure of the CM parent bodies was homogeneous.

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Carry, B.0000-0001-5242-3089
Additional Information:© 2019 B. Carry et al. Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Received 18 July 2018; Accepted 7 January 2019; Published online 20 March 2019. Based on observations made with (1) ESO Telescopes at the La Silla Paranal Observatory under programs 281.C-5011 (PI Dumas), 099.D-0098 (SPHERE GTO), and 199.C-0074(A) (PI Vernazza); and (2) the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. Some of the work presented here is based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programs 281.C-5011 (PI Dumas), 099.D-0098, (SPHERE GTO), and 199.C-0074(A) (PI Vernazza). Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. This research has made use of the Keck Observatory Archive (KOA), which is operated by the W. M. Keck Observatory and the NASA Exoplanet Science Institute (NExScI), under contract with the National Aeronautics and Space Administration. We thank the AGORA association which administrates the 60 cm telescope at Les Makes observatory, under a financial agreement with Paris Observatory. Thanks to A. Peyrot, J.-P. Teng for local support, and A. Klotz for helping with the robotizing. Some of these observations were acquired under grants from the National Science Foundation and NASA to W.J.M. (PI). B.C., A.D., J.G. and P.V. were supported by CNRS/INSU/PNP. J.H. and J.D. were supported by the grant 18-09470S of the Czech Science Foundation. The research leading to these results has received funding from the European Union’s Horizon 2020 Research and Innovation Programme, under Grant Agreement no 687378. This paper makes use of data from the DR1 of the WASP data (Butters et al. 2010) as provided by the WASP consortium, and the computing and storage facilities at the CERIT Scientific Cloud, reg. no. CZ.1.05/3.2.00/08.0144 which is operated by Masaryk University, Czech Republic. TRAPPIST-South is funded by the Belgian Fund for Scientific Research (Fond National de la Recherche Scientifique, FNRS) under the grant FRFC 2.5.594.09.F, with the participation of the Swiss FNS. TRAPPIST-North is a project funded by the University of Liège, and performed in collaboration with Cadi Ayyad University of Marrakesh. E.J. and M.G. are Belgian FNRS Senior Research Associates. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. Thanks to all the amateurs worldwide who regularly observe asteroid lightcurves and stellar occultations. Some co-authors of this study are amateurs who observed Daphne, and provided crucial data. The authors acknowledge the use of the Virtual Observatory tools Miriade 3 (Berthier et al. 2008), TOPCAT 4 , and STILTS 5 (Taylor 2005). This research used the SSOIS 6 facility of the Canadian Astronomy Data Centre operated by the National Research Council of Canada with the support of the Canadian Space Agency (Gwyn et al. 2012). Part of the data utilized in this publication were obtained and made available by the MIT-UH-IRTF Joint Campaign for NEO Reconnaissance, using SpeX spectrograph (Rayner et al. 2003). The IRTF is operated by the University of Hawaii under Cooperative Agreement no. NCC 5-538 with the National Aeronautics and Space Administration, Office of Space Science, Planetary Astronomy Program. The MIT component of this work is supported by NASA grant 09-NEOO009-0001, and by the National Science Foundation under Grant Nos. 0506716 and 0907766. We wish to acknowledge Professor Robert Groves, Director of Basic Languages (Classics) of the University of Arizona, for his assistance in selecting the name for Daphne’s satellite.
Group:Thirty Meter Telescope
Funding AgencyGrant Number
W. M. Keck FoundationUNSPECIFIED
Centre National de la Recherche Scientifique (CNRS)UNSPECIFIED
Institut National des Sciences de l'Univers (INSU)UNSPECIFIED
Grantová Agentura České Republiky18-09470S
European Research Council (ERC)687378
Fonds de la Recherche Scientifique (FNRS)FRFC 2.5.594.09.F
University of LiègeUNSPECIFIED
Canadian Space Agency (CSA)UNSPECIFIED
W. M. Keck FoundationUNSPECIFIED
Subject Keywords:minor planets, asteroids: general – minor planets, asteroids: individual: Daphne – methods: observational – techniques: high angular resolution
Record Number:CaltechAUTHORS:20200311-140912713
Persistent URL:
Official Citation:Homogeneous internal structure of CM-like asteroid (41) Daphne. B. Carry, F. Vachier, J. Berthier, M. Marsset, P. Vernazza, J. Grice, W. J. Merline, E. Lagadec, A. Fienga, A. Conrad, E. Podlewska-Gaca, T. Santana-Ros, M. Viikinkoski, J. Hanuš, C. Dumas, J. D. Drummond, P. M. Tamblyn, C. R. Chapman, R. Behrend, L. Bernasconi, P. Bartczak, Z. Benkhaldoun, M. Birlan, J. Castillo-Rogez, F. Cipriani, F. Colas, A. Drouard, J. Ďurech, B. L. Enke, S. Fauvaud, M. Ferrais, R. Fetick, T. Fusco, M. Gillon, E. Jehin, L. Jorda, M. Kaasalainen, M. Keppler, A. Kryszczynska, P. Lamy, F. Marchis, A. Marciniak, T. Michalowski, P. Michel, M. Pajuelo, P. Tanga, A. Vigan, B. Warner, O. Witasse, B. Yang and A. Zurlo. A&A, 623 (2019) A132; DOI:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:101860
Deposited By: Tony Diaz
Deposited On:11 Mar 2020 21:20
Last Modified:11 Mar 2020 21:20

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