Title: 'Are White Dwarf Binaries the Progenitors of Type IA Supernovae?'

While supernovae of type Ia (SNIa) play a prominent role in many astrophysical
environments and their use as cosmological tools is being pushed to redshift 1
and beyond, the nature of their progenitors remains substantially unknown. This
represents a major limitation both for understanding the astrophysical
phenomena in which SNIa are involved, and for their use as cosmological

In one of the two viable progenitor scenarios SNIa result from the merging of a
binary consisting of two white dwarfs (WD) exceeding a critical mass. However,
radial velocity (RV) searches for binary WDs at 2-4m class telescopes have so
far failed to produce a statistically significant sample. The aim of our
program is to carry out a high-resolution spectroscopic survey of about 1500
WDs with UVES in a snapshot fashion. This will produce the required factor of
10 improvement in sample size that we argue provides the ultimate test of the
binary WD scenario for SNIa and, more generally, for the understanding of
binary star evolution through mass and angular momentum losses via winds and
common envelope events. The obtained high-resolution spectra will offer the
unique opportunity to perform a systematic investigation of weak metal lines in
a large sample of WDs and to study the kinematics of the local WD population.

The sharp NLTE core of Halpha allows accurate RV measurements of hydrogen-rich
DA white dwarfs. This feature is not present in helium-rich DB white dwarfs.
However, the use of several helium lines enables us to reach a similar
accuracy. We will take two UVES spectra of every program star at two random
epochs separated by at least one day. The high resolution of UVES will enable
us to detect possible SNIa progenitor systems with a very high efficiency.
Follow-up observations of RV variable WDs are planned to determine the
system parameters of these binaries.