Understanding Accretion Variability Through TESS Observations of Taurus

TL;DR

This study analyzes TESS observations of Taurus T Tauri stars to link short-term brightness changes with accretion rate variations, emphasizing the importance of simultaneous multi-wavelength data for understanding accretion processes.

Contribution

It provides new insights into the connection between TESS-observed variability and accretion rates, incorporating multi-wavelength data and suggesting stratification in accretion columns.

Findings

Short-timescale variability correlates with accretion rate changes.

Evidence of time lags increasing at shorter wavelengths.

Contemporaneous multi-wavelength observations are essential.

Abstract

Interpreting the short-timescale variability of the accreting, young, low-mass stars known as Classical T Tauri stars remains an open task. Month-long, continuous light curves from the Transiting Exoplanet Survey Satellite (\textit{TESS}) have become available for hundreds of T Tauri stars. With this vast data set, identifying connections between the variability observed by \TESS and short-timescale accretion variability is valuable for characterizing the accretion process. To this end, we obtained short-cadence \TESS observations of 14 T Tauri stars in the Taurus star-formation region along with simultaneous ground-based, UBVRI-band photometry to be used as accretion diagnostics. In addition, we combine our dataset with previously published simultaneous NUV-NIR \textit{Hubble Space Telescope} spectra for one member of the sample. We find evidence that much of the short-timescale variability observed in the \TESS light curves can be attributed to changes in the accretion rate, but note significant scatter between separate nights and objects. We identify hints of time lags within our dataset that increase at shorter wavelengths which we suggest may be evidence of longitudinal density stratification of the accretion column. Our results highlight that contemporaneous, multi-wavelength observations remain critical for providing context for the observed variability of these stars.