  Testing 3D hydrodynamic models of stellar atmospheres is feasible by
retrieving spectral line shapes across stellar disks, using differential
spectroscopy during exoplanet transits. From synthetic data at hyper-high
spectral resolution, characteristic patterns for FeI and FeII lines were
identified in Paper IV from 3D models spanning T=3964-6726K (spectral types
approx. K8V-F3V). The observability of patterns among lines of different
strength, excitation potential and ionization level are now examined, as
observed at ordinary spectral resolutions and in the presence of noise. Time
variability in 3D atmospheres induces changes in spectral-line parameters, some
of which are correlated. An adequate calibration could identify proxies for the
jitter in apparent radial velocity to enable adjustments to actual stellar
radial motion. We also examined the center-to-limb temporal variability.
Recovery of spatially resolved line profiles with fitted widths and depths is
shown for various noise levels. Signals during exoplanet transit are simulated.
In addition to Rossiter-McLaughlin type signatures in apparent radial velocity,
analogous effects are shown for line depths and widths. From exoplanet
transits, overall stellar line parameters of width, depth and wavelength
position can be retrieved already with moderate efforts, but a very good
signal-to-noise ratio is required to reveal the more subtle signatures between
subgroups of spectral lines, where finer details of atmospheric structure are
encoded. In a solar model, temporal variability shows correlations between
jittering in apparent radial velocity and fluctuations in line depth. Since
both fluctuations in line depth and jittering in wavelength can be measured
from the ground, searches for low-mass exoplanets should explore these to
adjust apparent radial velocities to actual stellar motion.
