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Title: Correlating Changes in Spot Filling Factors with Stellar Rotation: The Case of LkCa 4
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.  more » « less
Award ID(s):
1950797
PAR ID:
10584827
Author(s) / Creator(s):
; ; ; ; ; ;
Publisher / Repository:
The Astrophysical Journal
Date Published:
Journal Name:
The Astrophysical Journal
Volume:
946
Issue:
1
ISSN:
0004-637X
Page Range / eLocation ID:
10
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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