Csillagászat (benne az asztrofizika és az űrtudomány)
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.
