PLANETARY COLLISIONS OUTSIDE THE SOLAR SYSTEM: TIME DOMAIN CHARACTERIZATION OF EXTREME DEBRIS DISKS

Luminous debris disksof warm dust in the terrestrial planetzones around solar-like stars were recently found to vary, which is indicative of ongoing large-scale collisions of rocky objects. We use Spitzer 3.6 and 4.5 μm time-series observations in 2012 and 2013 (extended to 2014 in one case) to monitor five more debris diskswith unusually high fractional luminosities (“extreme debris disk”), including P1121 in the open clusterM47 (80 Myr), HD 15407A in the AB Dor moving group (80 Myr), HD 23514 in the Pleiades(120 Myr), HD 145263 in the Upper Sco Association (10 Myr), and the field star BD+20 307 (≳1 Gyr). Together with the published results for ID8 in NGC 2547 (35 Myr), this makes the first systematic time-domain investigation of planetary impacts outside the solar system. Significant variations with timescales shorter than a year are detected in five out of the six extreme debris diskswe monitored. However, different systems show diverse sets of characteristics in the time domain, including long-term decay or growth, disk temperature variations, and possible periodicity.