Proposal #89

The Kepler-K2 spacecraft is close to exhausting its fuel and nearing the end of its mission. K2 Campaign 20 (C20), the last foreseen campaign with Kepler-K2, revisits the Taurus-Auriga star-forming region starting 2018 October 15 and, provided there remains enough fuel, runs through 2019 January 5. Unlike most K2 campaigns, C20 allows simultaneous observations from the ground. To compliment the K2 monochromatic light curves I propose to use SRO to obtain UBVRI optical imaging of a select few Taurus Young Stellar Objects (YSOs) daily over K2-C20. The science goal is to study accretion processes and disk-induced extinction events (dippers) using time-monitoring of optical colors along with coordinated ground-based optical and near-infrared spectroscopy. NASA has selected 61 of my proposed targets to be included in K2-C20, several of which are prime targets for coordinated ground-based monitoring. These include the actively accreting YSOs DR Tau and LkCa 15, and the G2e star V1025 Tau which hosts at least one exoplanet. I have an approved program on the Apache Point Observatory 3.5m to obtain R=3200 near-infrared spectroscopy on 13 nights distributed over C20 and am pursuing high-resolution optical spectroscopy on other facilities. Additional supporting optical imaging programs are in place (WIYN 0.9m and APO ARCSAT 0.5m) but these are block scheduled and do not span the breadth of K2-C20. The AAVSOnet SRO observations are crucial in obtaining the time-resolved (daily) color information necessary for complementing the K2 light curves. SRO observations enable color changes to be aligned with the physical processes (extinction and/or accretion events) displayed in the exquisite time resolved K2 light curves. The complimentary spectroscopy enable physical parameters to be measured from the emission and absorption line changes associated with these various events and to help pinpoint where these events are taking place within the complex star-accretion magnetosphere-disk environs. I request daily observations in UBVRI of the three Taurus members DR Tau, LkCa15, and V1025 Tau. Assuming the observations take 10 minutes to acquire, including associated overheads (slews, readouts, and exposure times), the requested observations require ~45 hours (15 hours per star) over the entire K2-C20 timeline spanning roughly 3 months starting mid-Oct. A team of 7 undergraduate CU students are involved in this project.