  The direct detection of a stellar system that explodes as a Type Ia supernova
(SN Ia) has not yet been successful. Various indirect methods have been used to
investigate SN Ia progenitor systems but none have produced conclusive results.
A prediction of single-degenerate models is that H- (or He-) rich material from
the envelope of the companion star should be swept up by the SN ejecta in the
explosion. Seven SNe Ia have been analysed to date looking for signs of H-rich
material in their late-time spectra and none were detected. We present results
from new late-time spectra of 11 SNe Ia obtained at the Very Large Telescope
using XShooter and FORS2. We present the tentative detection of H-alpha
emission for SN 2013ct, corresponding to ~0.007 Msun of stripped/ablated
companion star material (under the assumptions of the spectral modelling). This
mass is significantly lower than expected for single-degenerate scenarios,
suggesting that >0.1 Msun of H-rich is present but not observed. We do not
detect H-alpha emission in the other 10 SNe Ia. This brings the total sample of
normal SNe Ia with non-detections (<0.001-0.058 Msun) of H-rich material to 17
events. The simplest explanation for these non-detections is that these objects
did not result from the explosion of a CO white dwarf accreting matter from a
H-rich companion star via Roche-lobe overflow or symbiotic channels. However,
further spectral modelling is needed to confirm this. We also find no evidence
of He-emission features, but models with He-rich companion stars are not
available to place mass limits.
