Mémoire

Abstract

Studying comets is essential to improve our understanding of the early solar system. In this work, we performed photometry and image monitoring of two comets: the dynamically new comet C/2012 K1 (PanSTARRS) and the long-period returning comet C/2013 R1 (Lovejoy).

This was accomplished using images from the TRAPPIST-South telescope at the La Silla Observatory. The comets were monitored before, during and after their passage to perihelion, from March 2013 to December 2015 for PanSTARRS and from December 2013 to October 2014 for Lovejoy. Using TRAPPIST-South’s various cometary filters, we monitored the evolution of the brightness by computing apparent and heliocentric magnitudes in the broadband BVRI filters. The gas production rates of OH, CN, NH, C₃, and C₂ were also derived using narrowband gas filters, as well as gas abundance ratios.

Additionally, the production rate of water was inferred from that of OH. The dust activity was monitored through the Afρ parameter using R, RC, BC, and GC filters over extended periods and was compared to the cometary gas production by computing dust-to-gas ratios. Finally, the morphology of each comet’s coma was also analysed in the various filters using image enhancement techniques. This provided an in-depth characterisation of comets C/2012 K1 (PanSTARRS) and C/2013 R1 (Lovejoy).