Probing accretion variability in CR Cha with TESS and high-resolution spectroscopy

Young stellar objects are still surrounded by a circumstellar disk, from which material is accreting onto the stellar surface. This mass accretion process is essential in the formation and evolution of Sun-like stars. Although usually described with simple and static models, the accretion process is inherently time variable. Here, we present a multi-epoch analysis of CR Cha, a low-mass young stellar object with the age of 1-3 Myr. The aim of our work is to characterize the geometry and variability of the accretion process over a wide range of timescales in several accretion tracers using high-cadence photometric and high-resolution spectroscopic data. We analyse high-precision optical photometry obtained by the TESS space telescope, contemporaneous IJHK-band photometric measurements obtained by the SMARTS telescope, and combine these with high-resolution spectroscopic monitoring with the VLT/ESPRESSO and the 2.2m/FEROS spectrographs. Our extensive dataset allows us to examine the amplitude, timescale and pattern of variability in tracers which carry information on the distribution and the kinematics of the accreting material, the density structure of the inner disk, stellar activity, and the presence of outflows or jets. Where we have contemporaneous photometry and spectroscopy we link the photometric variability to spectroscopic variations. We complemented our data with spectropolarimetric observations from earlier years, which allow us to examine the role the large scale stellar magnetic field plays in the accretion process and to study spectroscopic variations over decadal timescales.