A long-term follow up of 174P/Echeclus

Centaur 174P/Echeclus, initially designated as (60558) 2000 EC98, presented three outbursts. A first and main one detected in 2005 December, another smaller one detected in 2011 May and a last one at the end of 2016 August. The first outburst was the largest one ever detected for a Centaur, of the order of 30 times that seen in other similar bodies. Because of the special interest of this target, and its brightness, we now have a large set of observational data were obtained before, during and after the two first outbursts. We present here new observational data obtained after the main outburst or coming from archives and an analysis of them. The main results of our study are (i) an absence of light curve in our 2013 data (while it was similar to 0.24 mag in the R-band in 2002-2003) and (ii) a satisfactory fit of the main outburst with two short events and a longer one (three sources of dust). Both results suggest a high obliquity of the rotation axis. We also discuss the origin of these outbursts and conclude that they are probably related to internal inhomogeneities of the nucleus.