Fundamental properties of young stars
Apparent age spreads in coeval young star-forming regions provide evidence for confounding factors absent from our understanding of young stars. We investigate the role of non-standard physics in the fundamental properties of young stars by measuring the areal coverage fraction and temperature contrast of starspots towards the weak-lined T-Tauri star LkCa 4. The approach involves forward modeling high-bandwidth, high-spectral resolution near-infrared IGRINS spectra with a composite mixture model for starspots and ambient photosphere. This approach yields estimates for areal coverage fractions of 75-85% cool stars spots possessing effective temperatures of about 2750 K. The remainder 15-25% of the surface with 4100 K can be thought of either as ambient photosphere or as a hot spot. These values are consistent with the observed spectral energy distribution, photometric modulation amplitude, and TiO variability in multi-epoch optical spectroscopy. The updated effective temperature and luminosities imply an older age for LkCa 4, though more evolutionary models incorporating starspots are needed. If longitudinally symmetric starspots (e.g. polar spots) are common among young stars, young stellar ages may be systematically underestimated, suggesting longer protoplanetary disk lifetimes.