1 research outputs found
Correlating Changes in Spot Filling Factors with Stellar Rotation: The Case of LkCa 4
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, . The best-fit models spanned two
photospheric component temperatures, = 4100 K (K7V) and 4400 K
(K5V), and one spot component temperature, = 3060 K (M5V) with an
of 0.3. We find values of to vary between 0.77 and 0.94 with
an average uncertainty of 0.04. The variability of is periodic
and correlates with its 3.374 day rotational period. Using a mean value for
to represent the total spot coverage, we calculated spot
corrected values for and . Placing these values alongside
evolutionary models developed for heavily spotted young stars, we infer mass
and age ranges of 0.45-0.6 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 estimating and 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.Comment: 21 pages, 9 Figures; Accepted for publication in Ap