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

Article

(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.

A&A 633(0), A65 (2020)

doi ↗ arXiv:1911.13049 ↗

Abstract

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.

Institute authors

Pejcha, Ondřej

Supported by

ERC 803158 — Cat-In-hAT: Catastrophic Interactions of Binary Stars and the Associated Transients, Horizon 2020 ERC Starting Grant 803158
MSMT LTAUSA18093 — Časová proměnnost v astronomii: účast v projektu All-Sky Automated Survey for Supernovae
Primus/17/SCI/17 — Teorie a pozorování astronomických tranzientů: supernovy z hmotných hvězd a splynutí hvězd

BibTeX

@article{UTF820,
  author        = {Hanuš, J. and Vernazza, P. and Viikinkoski, M. and Ferrais, M. and Rambaux, N. and Podlewska-Gaca, E. and Drouard, A. and Jorda, L. and Jehin, E. and Carry, B. and Marsset, M. and Marchis, F. and Warner, B. and Behrend, R. and Asenjo, V. and Berger, N. and Bronikowska, M. and Brothers, T. and Charbonnel, S. and Colazo, C. Coliac, J. -F. and Duffard, R. and Jones, A. and Leroy, A. and Marciniak, A. and Melia, R. and Molina, D. and Nadolny, J. and Person, M. and Pejcha, O. and Riemis, H. and Shappee, B. and Sobkowiak, K. and Soldán, F. and Suys, D. and Szakats, R. and Vantomme, J. and Birlan, M. and Berthier, J. and Bartczak, P. and Dumas, C. and Dudzinski, G. and Durech, J. and Castillo-Rogez, J. and Cipriani, F. and Fetick, R. and Fusco, T. and Grice, J. and Kaasalainen, M. and Kryszczynska, A. and Lamy, P. and Michalowski, T. and Michel, P. and Santana-Ros, T. and Tanga, P. and Vachier, F. and Vigan, A. and Witasse, O. and Yang, B.},
  title         = {{(704) Interamnia: a transitional object between a dwarf planet and a typical irregular-shaped minor body}},
  journal       = {A\&A},
  volume        = {633},
  number        = {0},
  pages         = {A65},
  year          = {2020},
  doi           = {10.1051/0004-6361/201936639},
  eprint        = {1911.13049},
  archivePrefix = {arXiv},
}