Publikace ÚTF

(704) Interamnia: a transitional object between a dwarf planet and a typical irregular-shaped minor body

Hanuš, J.; Vernazza, P.; Viikinkoski, M.; Ferrais, M.; Rambaux, N.; Podlewska-Gaca, E.; Drouard, A.; Jorda, L.; Jehin, E.; Carry, B.; Marsset, M.; Marchis, F.; Warner, B.; Behrend, R.; Asenjo, V.; Berger, N.; Bronikowska, M.; Brothers, T.; Charbonnel, S.; Colazo, C. Coliac, J. -F.; Duffard, R.; Jones, A.; Leroy, A.; Marciniak, A.; Melia, R.; Molina, D.; Nadolny, J.; Person, M.; Pejcha, O.; Riemis, H.; Shappee, B.; Sobkowiak, K.; Soldán, F.; Suys, D.; Szakats, R.; Vantomme, J.; Birlan, M.; Berthier, J.; Bartczak, P.; Dumas, C.; Dudzinski, G.; Durech, J.; Castillo-Rogez, J.; Cipriani, F.; Fetick, R.; Fusco, T.; Grice, J.; Kaasalainen, M.; Kryszczynska, A.; Lamy, P.; Michalowski, T.; Michel, P.; Santana-Ros, T.; Tanga, P.; Vachier, F.; Vigan, A.; Witasse, O.; Yang, B.

Context. With an estimated diameter in the 320-350 km range, (704) Interamnia is the fifth largest main belt asteroid and one of the few bodies that fills the gap in size between the four largest bodies with D > 400 km (Ceres, Vesta, Pallas and Hygiea) and the numerous smaller bodies with diameter =200 km. However, despite its large size, little is known about the shape and spin state of Interamnia and, therefore, about its bulk composition and past collisional evolution.
Aims: We aimed to test at what size and mass the shape of a small body departs from a nearly ellipsoidal equilibrium shape (as observed in the case of the four largest asteroids) to an irregular shape as routinely observed in the case of smaller (D = 200 km) bodies.
Methods: We observed Interamnia as part of our ESO VLT/SPHERE large program (ID: 199.C-0074) at thirteen different epochs. In addition, several new optical lightcurves were recorded. These data, along with stellar occultation data from the literature, were fed to the All-Data Asteroid Modeling algorithm to reconstruct the 3D-shape model of Interamnia and to determine its spin state.
Results: Interamnia's volume-equivalent diameter of 332 ± 6 km implies a bulk density of ? = 1.98 ± 0.68 g cm-3, which suggests that Interamnia - like Ceres and Hygiea - contains a high fraction of water ice, consistent with the paucity of apparent craters. Our observations reveal a shape that can be well approximated by an ellipsoid, and that is compatible with a fluid hydrostatic equilibrium at the 2s level.
Conclusions: The rather regular shape of Interamnia implies that the size and mass limit, under which the shapes of minor bodies with a high amount of water ice in the subsurface become irregular, has to be searched among smaller (D = 300 km) less massive (m = 3 × 1019 kg) bodies.
journal:Astronomy & Astrophysics
grants:Cat-In-hAT: Catastrophic Interactions of Binary Stars and the Associated Transients, Horizon 2020 ERC Starting Grant 803158; 2019-2023; hlavní řešitel: Ondřej Pejcha
Časová proměnnost v astronomii: účast v projektu All-Sky Automated Survey for Supernovae; 2019-2022; hlavní řešitel: Ondřej Pejcha
Teorie a pozorování astronomických tranzientů: supernovy z hmotných hvězd a splynutí hvězd, Primus/17/SCI/17; 2017-2019; hlavní řešitel: Ondřej Pejcha
hanus_etal_including_pejcha_aa36639-19.pdf (7531.79 kB)

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