A thermophysical and dynamical study of the Hildas, (1162) Larissa, and (1911) Schubart

Chavez, Cristian F. and Muller, T. G. and Marshall, J. P. and Horner, J. and Drass, H. and Carter, B. ORCID: https://orcid.org/0000-0003-0035-8769 (2021) A thermophysical and dynamical study of the Hildas, (1162) Larissa, and (1911) Schubart. Monthly Notices of the Royal Astronomical Society, 502 (4). pp. 4981-4992. ISSN 0035-8711

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Abstract

The Hilda asteroids are among the least studied populations in the asteroid belt, despite their potential importance as markers of Jupiter's migration in the early Solar system. We present new mid-infrared observations of two notable Hildas, (1162) Larissa, and (1911) Schubart, obtained using the Faint Object infraRed CAmera for the SOFIA Telescope (FORCAST), and use these to characterize their thermal inertia and physical properties. For (1162) Larissa, we obtain an effective diameter of 46.5 $^{+2.3}_{-1.7}$ km, an albedo of 0.12 ± 0.02, and a thermal inertia of 15 $^{+10}_{-8}$ Jm-2 s1/2 K-1. In addition, our Larissa thermal measurements are well matched with an ellipsoidal shape with an axial ratio a/b = 1.2 for the most-likely spin properties. Our modelling of (1911) Schubart is not as refined, but the thermal data point towards a high-obliquity spin-pole, with a best fit a/b = 1.3 ellipsoidal shape. This spin-shape solution is yielding a diameter of 72 $^{+3}_{-4}$ km, an albedo of 0.039± 0.02, and a thermal inertia below 30 Jm-2 s1/2 K-1 (or 10 $^{+20}_{-5}$ Jm-2 s1/2 K-1). As with (1162) Larissa, our results suggest that (1911) Schubart is aspherical, and likely elongated in shape. Detailed dynamical simulations of the two Hildas reveal that both exhibit strong dynamical stability, behaviour that suggests that they are primordial, rather than captured objects. The differences in their albedos, along with their divergent taxonomical classification, suggests that despite their common origin, the two have experienced markedly different histories.


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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: C. 2021 The Author(s). Published version deposited in accordance with the copyright policy of the publisher.
Faculty/School / Institute/Centre: Current - Institute for Advanced Engineering and Space Sciences - Centre for Astrophysics (1 Aug 2018 -)
Faculty/School / Institute/Centre: Current - Institute for Advanced Engineering and Space Sciences - Centre for Astrophysics (1 Aug 2018 -)
Date Deposited: 21 Jul 2021 03:20
Last Modified: 22 Jul 2021 02:07
Uncontrolled Keywords: radiation mechanisms: thermal; minor planets; asteroids; (1162) Larissa; (1911) Schubart;
Fields of Research (2008): 02 Physical Sciences > 0201 Astronomical and Space Sciences > 020108 Planetary Science (excl. Extraterrestrial Geology)
Fields of Research (2020): 51 PHYSICAL SCIENCES > 5109 Space sciences > 510905 Solar system planetary science (excl. planetary geology)
Socio-Economic Objectives (2008): E Expanding Knowledge > 97 Expanding Knowledge > 970102 Expanding Knowledge in the Physical Sciences
Socio-Economic Objectives (2020): 28 EXPANDING KNOWLEDGE > 2801 Expanding knowledge > 280120 Expanding knowledge in the physical sciences
Identification Number or DOI: https://doi.org/10.1093/mnras/stab251
URI: http://eprints.usq.edu.au/id/eprint/42825

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