Properties of slowly rotating asteroids from the Convex Inversion Thermophysical Model^★

¹ Astronomical Observatory Institute, Faculty of Physics, A. Mickiewicz University, Słoneczna 36, 60-286 Poznań, Poland
e-mail: am@amu.edu.pl
² Astronomical Institute, Faculty of Mathematics and Physics, Charles University, V Holešovičkách 2, 180 00 Prague 8, Czech Republic
³ Max-Planck-Institut für Extraterrestrische Physik (MPE), Giessenbachstrasse 1, 85748 Garching, Germany
⁴ Mt. Suhora Observatory, Pedagogical University, Podchorążych 2, 30-084 Cracow, Poland
⁵ Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Eőtvős Loránd Research Network (ELKH), 1121 Budapest, Konkoly Thege Miklós út 15-17, Hungary
⁶ MTA CSFK Lendület Near-Field Cosmology Research Group, Hungary
⁷ ELTE Eötvös Loránd University, Institute of Physics, 1117, Pázmány Péter sétány 1/A, Budapest, Hungary
⁸ Astronomy Department, Eötvös Loránd University, Pázmány P. s. 1/A, 1171 Budapest, Hungary
⁹ Observatório Nacional, R. Gen. José Cristino, 77 - São Cristóvão, 20921-400, Rio de Janeiro - RJ, Brazil
¹⁰ Geneva Observatory, 1290 Sauverny, Switzerland
¹¹ Oukaimeden Observatory, High Energy Physics and Astrophysics Laboratory, Cadi Ayyad University, Marrakech, Morocco
¹² Les Engarouines Observatory, 84570 Mallemort-du-Comtat, France
¹³ Collonges Observatory, 74160 Collonges, France
¹⁴ Flarestar Observatory Fl.5/B, George Tayar Street, San Gwann SGN 3160, Malta
¹⁵ Stazione Astronomica, 28060 Sozzago (Novara), Italy
¹⁶ Haute-Provence Observatory, St-Michel l’Observatoire, France
¹⁷ Departamento de Sistema Solar, Instituto de Astrofísica de Andalucía (CSIC), Glorieta de la Astronomía s/n, 18008 Granada, Spain
¹⁸ 11 rue du Puits Coellier, 37550 Saint-Avertin, France
¹⁹ Observatoire du Bois de Bardon, 16110 Taponnat, France
²⁰ Association T60, Observatoire Midi-Pyrénées, 14, avenue Edouard Belin, 31400 Toulouse, France
²¹ Aix Marseille Université, CNRS, CNES, Laboratoire d’Astrophysique de Marseille, Marseille, France
²² Instituto de Astrofísica de Canarias, C/ Vía Lactea, s/n, 38205 La Laguna, Tenerife, Spain
²³ Gran Telescopio Canarias (GRANTECAN), Cuesta de San José s/n, 38712 Breña Baja, La Palma, Spain
²⁴ Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University in Toruń, Poland
²⁵ School of Physical Sciences, The Open University, MK7 6AA, UK
²⁶ Space sciences, Technologies and Astrophysics Research Institute, Université de Liège, Allée du 6 Août 17, 4000 Liège, Belgium
²⁷ Institute of Physics, Jan Kochanowski University, ul. Uniwersytecka 7, 25-406 Kielce, Poland
²⁸ Chungbuk National University, 1, Chungdae-ro, Seowon-gu, Cheongju-si, Chungcheongbuk-do, Republic of Korea
²⁹ Korea Astronomy and Space Science Institute, 776 Daedeok-daero, Yuseong-gu, Daejeon 34055, Korea
³⁰ Institute of Physics, Faculty of Natural Sciences, University of P. J. Šafárik, Park Angelinum 9, 040 01 Košice, Slovakia
³¹ Laboratory of Space Researches, Uzhhorod National University, Daleka st. 2a, 88000, Uzhhorod, Ukraine
³² Dept. Astrofisica, Universidad de La Laguna, 38206 La Laguna, Tenerife, Spain
³³ Institute of Theoretical Physics and Astronomy, Vilnius University, Saulėtekio al. 3, 10257 Vilnius, Lithuania
³⁴ Organ Mesa Observatory, 4438 Organ Mesa Loop, Las Cruces, New Mexico 88011, USA
³⁵ Command Module Observatory, 121 W. Alameda Dr., Tempe, AZ 85282, USA
³⁶ Observatoire de Blauvac, 293 chemin de St Guillaume, 84570 St-Estève, France
³⁷ Departamento de Física, Ingeniería de Sistemas y Teoría de la Señal, Universidad de Alicante, Alicante, Spain
³⁸ Institut de Ciències del Cosmos, Universitat de Barcelona (IEEC-UB), Barcelona, Spain
³⁹ Lowell Observatory, 1400 West Mars Hill Road, Flagstaff, Arizona, 86001 USA
⁴⁰ Department of Physics, Adiyaman University, 02040 Adiyaman, Turkey
⁴¹ European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching bei München, Germany
⁴² Japan Spaceguard Association, Bisei Spaceguard Center, 1716-3, Okura, Bisei, Ibara, Okayama 714-1411, Japan
⁴³ Kepler Institute of Astronomy, University of Zielona Góra, Lubuska 2, 65-265 Zielona Góra, Poland

Received: 2 April 2021
Accepted: 20 June 2021

Abstract

Context. Recent results for asteroid rotation periods from the TESS mission showed how strongly previous studies have underestimated the number of slow rotators, revealing the importance of studying those targets. For most slowly rotating asteroids (those with P > 12 h), no spin and shape model is available because of observation selection effects. This hampers determination of their thermal parameters and accurate sizes. Also, it is still unclear whether signatures of different surface material properties can be seen in thermal inertia determined from mid-infrared thermal flux fitting.

Aims. We continue our campaign in minimising selection effects among main belt asteroids. Our targets are slow rotators with low light-curve amplitudes. Our goal is to provide their scaled spin and shape models together with thermal inertia, albedo, and surface roughness to complete the statistics.

Methods. Rich multi-apparition datasets of dense light curves are supplemented with data from Kepler and TESS spacecrafts. In addition to data in the visible range, we also use thermal data from infrared space observatories (mainly IRAS, Akari and WISE) in a combined optimisation process using the Convex Inversion Thermophysical Model. This novel method has so far been applied to only a few targets, and therefore in this work we further validate the method itself.

Results. We present the models of 16 slow rotators, including two updated models. All provide good fits to both thermal and visible data.The obtained sizes are on average accurate at the 5% precision level, with diameters found to be in the range from 25 to 145 km. The rotation periods of our targets range from 11 to 59 h, and the thermal inertia covers a wide range of values, from 2 to <400 J m⁻² s^−1∕2 K⁻¹, not showing any correlation with the period.

Conclusions. With this work we increase the sample of slow rotators with reliable spin and shape models and known thermal inertia by 40%. The thermal inertia values of our sample do not display a previously suggested increasing trend with rotation period, which mightbe due to their small skin depth.