Starspots as an Explanation for the Mysterious IYJ Continuum Excess Emission in Classical T Tauri Stars

TL;DR

This study models the near-infrared spectra of Classical T Tauri Stars, demonstrating that including starspots in the models explains the IYJ excess emission without needing additional intermediate temperature components.

Contribution

The paper introduces new spectral models that incorporate starspots, accretion hot-spots, and warm inner disks to accurately reconstruct the spectra of accreting low-mass stars.

Findings

Starspots explain the IYJ excess emission.

Proper starspot treatment removes the need for intermediate temperature components.

Revised continuum excess estimates improve stellar parameter derivations.

Abstract

An accurate estimation of the continuum excess emission from accretion spots and inner circumstellar disk regions is crucial for a proper derivation of fundamental stellar parameters in accreting systems. However, the presence of starspots can make disentangling the complicated multi-component emission in these systems challenging. Subtraction of a single-temperature spectral template is insufficient to account for the composite stellar emission, as we demonstrated in a recent campaign involving Weak-Lined T Tauri Stars. Here, we model the moderate resolution near-infrared spectra of Classical T Tauri Stars, presenting new spectral models that incorporate spotted stars plus emission from accretion hot-spots and a warm inner disk, allowing us to simultaneously reconstruct the entire 0.8-2.4 micrometer spectrum of our sixteen targets. Using these models, we re-derive the continuum excess emission. Our results indicate that accounting for starspots resolves the need to include a previously proposed intermediate temperature component in the IYJ excess, and highlights the importance of a proper treatment of starspots in studies of accreting low-mass stars.