Research Note

Photometric analysis for the spin and shape parameters of the C-type main-belt asteroids (171) Ophelia and (360) Carlova

¹ Yunnan Observatories, Chinese Academy of Sciences, PO Box 110, 650011 Kunming, PR China
e-mail: wangxb@ynao.ac.cn
² Key laboratory for the structure and evolution of celestial objects, Chinese Academy of Sciences, 650011 Kunming, PR China
³ Department of Physics, PO Box 64, 00014 University of Helsinki, Finland
e-mail: karri.muinonen@helsinki.fi
⁴ Finnish Geodetic Institute, PO Box 15, 02431 Masala, Finland
⁵ University of Chinese Academy of Sciences, 100049 Beijing, PR China
⁶ Genève Observatory, 1290 Sauverny, Switzerland
⁷ Linhaceira Observatorie, Instituto Politecnico de Tomar, 2300-313 Tomar, Portugal
⁸ Kingsgrove observatory, 23 Monaro Ave., Kingsgrove, NSW 2208, Australia
⁹ Observatoire de Bédoin, 47 rue Guillaume Puy, 84000 Avignon, France
¹⁰ Observatoire du Tim, Chemin La Chapelle, 04700 Puimichel, France
¹¹ Stazione Astronomica di Sozzago, 28060 Sozzago, Italy
¹² Institut d’Astrophysique et de Géophysique, Université de Liège, 4000 Liège, Belgium
¹³ Centre Astronomique de La Couyère, 35320 La Couyère, France
¹⁴ Institut de Recherche en Astrophysique et Planétologie (IRAP), Université de Toulouse, 9 avenue du colonel Roche, 31028 Toulouse Cedex 4, France
¹⁵ Observatoire de Haute-Provence, 04870 Saint Michel l’ Observatoire, France
¹⁶ Observatoire Midi-Pyrénées and Association T60, Pic du Midi, 65200 Bagnères-de-Bigorre, France

Received: 13 May 2015
Accepted: 29 June 2015

Abstract

Aims. Two C-type main-belt asteroids (171) Ophelia and (360) Carlova are studied for their spin parameters and shapes in the present paper. Although it was suspected that Ophelia was a binary system owing to the eclipse features in the light curve obtained in 1977, no direct evidence has been obtained to confirm the binarity. To verify the previous findings, the spin parameters and shape of Ophelia are derived by analyzing the photometric data. To understand the dispersion in the previous determination of Carlova’s spin parameters, new observational data and existing photometric data are reanalyzed to find a homogenous solution for its spin parameters and shape.

Methods. The spin parameters and shapes of two asteroids were determined from photometric data using the convex inversion technique. The simplified virtual-observation Markov chain Monte Carlo method was applied to estimate the uncertainties of the spin parameters and to understand the divergence of derived shapes.

Results. A pair of possible poles for Ophelia are derived, the spin periods corresponding to the two poles are nearly the same. The convex shape of Ophelia shows binary characteristics. For Carlova, a unique pole solution and its convex shape are ascertained together with the occultation observations. The convex shape of Carlova shows that it is a rough ellipsoid.