We analyze the photometric and spectroscopic variability of the classical T
Tauri star V2129 Oph over several rotational cycles to test the dynamical
predictions of magnetospheric accretion models. The photometric variability and
the radial velocity variations in the photospheric lines can be explained by
rotational modulation due to cold spots, while the radial velocity variations
of the He I (5876 \AA) line and the veiling variability are due to hot spot
rotational modulation. The hot and cold spots are located at high latitudes and
about the same phase, but the hot spot is expected to sit at the chromospheric
level, while the cold spot is at the photospheric level. Using the
dipole+octupole magnetic-field configuration previously proposed in the
literature for the system, we compute 3D MHD magnetospheric simulations of the
star-disk system. We use the simulation's density, velocity and scaled
temperature structures as input to a radiative transfer code, from which we
calculate theoretical line profiles at all rotational phases. The theoretical
profiles tend to be narrower than the observed ones, but the qualitative
behavior and the observed rotational modulation of the H\alpha and H\beta
emission lines are well reproduced by the theoretical profiles. The
spectroscopic and photometric variability observed in V2129 Oph support the
general predictions of complex magnetospheric accretion models with
non-axisymmetric, multipolar fields.Comment: Accepted by Astronomy and Astrophysic