%APérez Paolino, Facundo%ABary, Jeffrey%APetersen, Michael%AWard-Duong, Kimberly%ATofflemire, Benjamin%AFollette, Katherine%AMach, Heidi%BJournal Name: The Astrophysical Journal; Journal Volume: 946; Journal Issue: 1; Related Information: CHORUS Timestamp: 2024-01-16 12:32:32
%D2023%IDOI PREFIX: 10.3847
%JJournal Name: The Astrophysical Journal; Journal Volume: 946; Journal Issue: 1; Related Information: CHORUS Timestamp: 2024-01-16 12:32:32
%K
%MOSTI ID: 10402697
%PMedium: X; Size: Article No. 10
%TCorrelating Changes in Spot Filling Factors with Stellar Rotation: The Case of LkCa 4
%X
Abstract
We present a multi-epoch spectroscopic study of LkCa 4, a heavily spotted non-accreting T Tauri star. Using SpeX at NASA’s Infrared Telescope Facility (IRTF), 12 spectra were collected over five consecutive nights, spanning ≈1.5 stellar rotations. Using the IRTF SpeX Spectral Library, we constructed empirical composite models of spotted stars by combining a warmer (photosphere) standard star spectrum with a cooler (spot) standard weighted by the spot filling factor,fspot. The best-fit models spanned two photospheric component temperatures,Tphot= 4100 K (K7V) and 4400 K (K5V), and one spot component temperature,Tspot= 3060 K (M5V) with anAVof 0.3. We find values offspotto vary between 0.77 and 0.94 with an average uncertainty of ∼0.04. The variability offspotis periodic and correlates with its 3.374 day rotational period. Using a mean value forfmeanspotto represent the total spot coverage, we calculated spot corrected values forTeffandL⋆. Placing these values alongside evolutionary models developed for heavily spotted young stars, we infer mass and age ranges of 0.45–0.6M⊙and 0.50–1.25 Myr, respectively. These inferred values represent a twofold increase in the mass and a twofold decrease in the age as compared to standard evolutionary models. Such a result highlights the need for constraining the contributions of cool and warm regions of young stellar atmospheres when estimatingTeffandL⋆to infer masses and ages as well as the necessity for models to account for the effects of these regions on the early evolution of low-mass stars.
%0Journal Article