# # Program information file # PROGRAM_ID 2022B091 PROGRAM_TITLE Constraining the Effects of Large Cool Spots on the Early Evolution of Sun-like Stars PROGRAM_INV1 Jeff Bary PROGRAM_INV2 Facundo Perez PROGRAM_INV3 Kimberly Ward-Duonng PROGRAM_INV4 Kevin Covey PROGRAM_INV5 Michael Petersen PROGRAM_SCICAT stellar PROGRAM_ABSTRACT_BEG We propose to monitor five non-accreting young, Sun-like stars with evidence for large cool spots using SpeX SXD. Spectra spanning multiple or nearly full rotation periods will be acquired for all sources. Previous work has established a correlation between spot-sensitive spectral features such as TiO and FeH bands in the near-IR and 'instantaneous' spot filling factors. Multi-epoch spectra collected over a complete stellar rotation provide better constraints on the 'total' spot coverage. The total spot coverage is an important factor in determining the effective temperature and luminosity of a spotted star. Placing these stellar parameters on evolutionary tracks is one of the standard processes by which the masses and ages of young stars are determined. New evolutionary models that include the evolutionary effects of spots require measurements of total spot coverages and spot-corrected temperatures and luminosities to constrain the ages and masses of spotted stars. At present, only one star has the multi-epoch spectral observations necessary to constrain the 'total' spot coverage. The program we propose will increase the sample to five stars including two sources with dynamical mass measurements for comparison. All targets are bright in the infrared permitting easy acquisition and total integration times that will permit us to acquire two epochs [in the case of one source three] over the course of one half-night. PROGRAM_ABSTRACT_END