The Centaur 10199 Chariklo: Investigation into rotational period, absolute magnitude, and cometary activity

Context. Rings have recently been discovered around the Centaur 10199 Chariklo. Aims. In this paper we present new photometric data, obtained at the 4.2 m SOAR Telescope, aiming to investigate Chariklo's absolute magnitude and rotational period, which is still unknown, and to look for potential cometary activity. Methods. The field background of the images was very crowded so several approaches were used for the extraction of Chariklo fluxes. The background sources were subtracted using difference image analysis and then aperture photometry was applied. A Fourier polynomial fit was used to determine the period. Results. We find a synodic rotation period of 7.004±0.036 h. The visual absolute magnitude derived from the SOAR data is H_v = 7.03 ± 0.10. We model the rings' contribution to the flux, and find that the derived H_v is consistent with the predicted ring system aspect angle. We also revised the Chariklo system albedo (4.2%) and effective radius (119 ± 5 km) from a re-analysis of Herschel and WISE thermal data obtained during 2010 with the correct H_v value. No coma is detected from the SOAR data, nor in previous VLT images acquired in 2007-2008, where the rings' aspect angle was close to zero. The upper limit to the dust production rate is 2.5 kg/s.