Name/Affiliation: Richard Gray, Christopher Corbally, Jon Saken (Appalachian State University)
The Young Solar Analogs Project
The Young Solar Analogs project (Appalachian State University, Vatican Observatory) has monitored 31 solar-type stars with ages between 300 Myr and 1.5 Gyr since 2007. The ultimate goal of the project is to give insight into the conditions in the early solar system when life was establishing a foothold on the earth. That early life had to contend with a hostile space environment: strong X-ray and UV fluxes, irradiance variations one to two orders of magnitude greater than seen today, and strong flares and coronal mass ejections. From the beginning we have been monitoring our set of young late F- to early K-dwarfs spectroscopically at Ca II H & K and in the G-band. We began monitoring these stars photometrically in a 5-band system (Stromgren-v, Johnson-Cousins B, V, and R, and narrow-band H-alpha) in 2011. Recently, we started high-cadence, high-S/N spectroscopy of our program stars with the Vatican Advanced Technology Telescope, and are experimenting with high-cadence photometry in order to detect and characterize flares. After nearly 7 years of monitoring we see a variety of stellar cycling behavior in both Ca H & K and in the G-band. We have also determined rotational periods, detected differential rotation, and have evidence for active longitudes in a number of our program stars. Many of our stars also show periods between 30 and 60 days that may be related to the convective overturn timescale. We have confirmed for many of our stars the results of the Lowell SSS project that found that young solar-type stars are fainter at activity maximum, opposite to the behavior of the sun. We have found that this inverse behavior extends to rotational modulation -- these young stars brighten when a large spot passes across the visible hemisphere. We will also review early results from our high cadence program.