# Summary of K2 Program GO15043 Title: Planet Evolution and Fundamental Stellar Parameters at 10-20 Myr After Formation PI: Rizzuto, Aaron C (University of Texas at Austin) CoIs: Ireland, Michael James; Jensen, Eric L; Muirhead, Philip Steven; Mann, Andrew Withycombe; Kraus, Adam L; Covey, Kevin The Sco-Cen OB association is the nearest (d=145 pc) region of recently completed stars formation to the sun, and spans thousands of square degrees on the sky. The association consists of three subgroups: Upper Scorpius (US 11 Myr), Upper Centaurus Lupus (UCL 15-20 Myr) and Lower-Centaurus-Crux (LCC 15-20 Myr), which contain ~800 B, A and F-type stars and based on IMF extrapolation, ~10000 lower mass stars which are mostly unidentified. The vast majority of pre main sequence stars in the nearest 200 pc volume are thus comoving Sco-Cen members waiting to be found. The K2 mission is ideal for measuring planet formation timescales and migration pathways. Over the completed and planned campaigns, multiple groups of young stars have been or will be observed by K2, ranging from ~2 Myr old Taurus star forming, through the ~120 Myr old Pleiades, and the ~600 Myr old Hyades moving group. The detected, and soon to be detected exoplanets in these samples of different age will reveal the evolution of the exoplanet population in the early stages of stellar life. The K2 mission has also already observed the Upper Scorpius subgroup with very fruitful results: We identified the current youngest transiting exoplanet, hosted by an Upper Sco M-type star K2-33 b (Mann et al., 2016) and multiple eclipsing binaries were characterized (e.g., Kraus et al., 2015, David et al., 2015). We propose to use K2 in campaign 15, in long-cadence mode, to search further confirmed and probable Upper Scorpius and UCL members for young transiting exoplanets. We have already developed tools, which we have applied to existing data, to extract lightcurves from K2 data and remove instrumental systematics. We have also developed methods for removing stellar activity signals from the lightcurves of young stars, and have identified candidate transiting exoplanets in the K2 Upper Scorpius data from campaign 2. We have planned a robust follow-up campaign for any detected Sco-Cen planets, utilizing a full suite of techniques including multi-band ground based photometry to confirm the planetary nature of the transits, and high-resolution imaging and IR spectroscopy to detect stellar companions. We also expect to discover ~5 eclipsing binary systems in the proposed sample, which, with ground based follow-up, will offer revolutionary constraints at the youngest reaches of the pre-main sequence evolutionary models. We are already following up 10 eclipsing binaries in Upper Scorpius from K2 campaign 2, and a further 20 in older nearby clusters. We will add any new eclipsing binaries in Sco-Cen from C15 to this program. We have built a complete census of confirmed Sco-Cen members from all of the existing literature and our own spectroscopic confirmation, and have supplemented this with a kinematic search for high confidence candidate new members (following the method of Rizzuto et al. 2011,2015). In total, we propose to observe 578 targets with 9