Thermal properties of slowly rotating asteroids: results from a targeted survey^★

¹ Astronomical Observatory Institute, Faculty of Physics, A. Mickiewicz University, Słoneczna 36, 60-286 Poznań, Poland
e-mail: am@amu.edu.pl
² Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstrasse 1, 85748 Garching, Germany
³ Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Hungarian Academy of Sciences, 1121 Budapest, Konkoly Thege Miklós út 15-17, Hungary
⁴ MTA CSFK Lendület Near-Field Cosmology Research Group, Budapest, Hungary
⁵ Astronomy Department, Eötvös Loránd University, Pázmány P. s. 1/A, 1171 Budapest, Hungary
⁶ Institute of Physics, University of Szczecin, Wielkopolska 15, 70-453 Szczecin, Poland
⁷ The IEA, University of Reading, Philip Lyle Building, Whiteknights Campus, Reading, RG6 6BX, UK
⁸ Observatoire des Hauts Patys, 84410 Bédoin, France
⁹ Villefagnan Observatory, Villefagnan, France
¹⁰ Geneva Observatory, 1290 Sauverny, Switzerland
¹¹ Les Engarouines Observatory, 84570 Mallemort-du-Comtat, France
¹² Stazione Astronomica di Sozzago, 28060 Sozzago, Italy
¹³ Departamento de Sistema Solar, Instituto de Astrofísica de Andalucía (CSIC), Glorieta de la Astronomía s/n, 18008 Granada, Spain
¹⁴ Rose-Hulman Institute of Technology, CM 171 5500 Wabash Ave., Terre Haute, IN 47803, USA
¹⁵ Observatoire du Bois de Bardon, 16110 Taponnat, France
¹⁶ Elgin Observatory, 1155 Hartford St; Elgin, OR USA
¹⁷ Instituto de Astrofísica de Canarias, C/ Vía Lactea, s/n, 38205 La Laguna, Tenerife, Spain
¹⁸ Gran Telescopio Canarias (GRANTECAN), Cuesta de San José s/n, 38712 Breña Baja, La Palma, Spain
¹⁹ Lincaheira Observatory, Instituto Politécnico de Tomar, 2300-313 Tomar, Portugal
²⁰ School of Physical Sciences, The Open University, MK7 6AA, UK
²¹ Chungbuk National University, 1, Chungdae-ro, Seowon-gu, Cheongju-si, Chungcheongbuk-do, Republic of Korea
²² Korea Astronomy and Space Science Institute, 776 Daedeokdae-ro, Yuseong-gu, 305-348 Daejeon, Korea
²³ Institute of Physics, Faculty of Natural Sciences, University of P. J. Šafárik, Park Angelinum 9, 040 01 Košice, Slovakia
²⁴ Laboratory of Space Researches, Uzhhorod National University, Daleka st. 2a, 88000, Uzhhorod, Ukraine
²⁵ Observatorio de Albox, Almeria, Spain
²⁶ Observatório Nacional Rua General José Cristino, 77, 20921-400 Bairro Imperial de São Cristóvão Rio de Janeiro, RJ, Brasil
²⁷ Mt. Suhora Observatory, Pedagogical University, Podchorążych 2, 30-084 Cracow, Poland
²⁸ Organ Mesa Observatory, 4438 Organ Mesa Loop, Las Cruces, New Mexico 88011, USA
²⁹ Command Module Observatory, 121 W. Alameda Dr., Tempe, AZ 85282, USA
³⁰ Observatoire de Blauvac, 293 chemin de St Guillaume, 84570 St-Estève, France
³¹ Lowell Observatory, 1400 West Mars Hill Road, Flagstaff, AZ 86001, USA
³² Department of Physics, University of Adiyaman, 02040 Adiyaman, Turkey
³³ Bisei Spaceguard Center, Japan Spaceguard Association, 1716-3, Okura, Bisei, Ibara, Okayama 714-1411, Japan
³⁴ Kepler Institute of Astronomy, University of Zielona Góra, Lubuska 2, 65-265 Zielona Góra, Poland

Received: 25 January 2019
Accepted: 9 April 2019

Abstract

Context. Earlier work suggests that slowly rotating asteroids should have higher thermal inertias than faster rotators because the heat wave penetrates deeper into the subsurface. However, thermal inertias have been determined mainly for fast rotators due to selection effects in the available photometry used to obtain shape models required for thermophysical modelling (TPM).

Aims. Our aims are to mitigate these selection effects by producing shape models of slow rotators, to scale them and compute their thermal inertia with TPM, and to verify whether thermal inertia increases with the rotation period.

Methods. To decrease the bias against slow rotators, we conducted a photometric observing campaign of main-belt asteroids with periods longer than 12 h, from multiple stations worldwide, adding in some cases data from WISE and Kepler space telescopes. For spin and shape reconstruction we used the lightcurve inversion method, and to derive thermal inertias we applied a thermophysical model to fit available infrared data from IRAS, AKARI, and WISE.

Results. We present new models of 11 slow rotators that provide a good fit to the thermal data. In two cases, the TPM analysis showed a clear preference for one of the two possible mirror solutions. We derived the diameters and albedos of our targets in addition to their thermal inertias, which ranged between 3₋₃⁺³³ and 45₋₃₀⁺⁶⁰ J m⁻² s^−1∕2 K⁻¹.

Conclusions. Together with our previous work, we have analysed 16 slow rotators from our dense survey with sizes between 30 and 150 km. The current sample thermal inertias vary widely, which does not confirm the earlier suggestion that slower rotators have higher thermal inertias.