The reactivation of main-belt Comet 324P/La Sagra (P/2010 R2)

We present observations using the Baade Magellan and Canada-France-Hawaii telescopes showing that main-belt comet 324P/La Sagra, formerly known as P/2010 R2, has become active again for the first time since originally observed to be active in 2010-2011. The object appears point-source-like in 2015 March and April as it approached perihelion (true anomaly of nu similar to 300 degrees), but was similar to 1 mag brighter than expected if inactive, suggesting the presence of unresolved dust emission. Activity was confirmed by observations of a cometary dust tail in 2015 May and June. We find an apparent net dust production rate of (M) over dot(d) less than or similar to 0.1 kg s(-1) during these observations. 324P is now the fourth main-belt comet confirmed to be recurrently active, a strong indication that its activity is driven by sublimation. It now has the largest confirmed active range of all likely main-belt comets, and also the most distant confirmed inbound activation point at R similar to 2.8 au. Further observations during the current active period will allow direct comparisons of activity strength with 324P's 2010 activity.