  Recent studies of the stellar population in the solar neighborhood (<20 pc)
suggest that there are undetected white dwarfs (WDs) in multiple systems with
main sequence companions. Detecting these hidden stars and obtaining a more
complete census of nearby WDs is important for our understanding of binary and
galactic evolution, as well as the study of explosive phenomena. In an attempt
to uncover these hidden WDs, we present intermediate resolution spectroscopy
over the wavelength range 3000-25000 \AA\ of 101 nearby M dwarfs (dMs),
observed with the Very Large Telescope X-Shooter spectrograph. For each star we
search for a hot component superimposed on the dM spectrum. X-Shooter has
excellent blue sensitivity and thus can reveal a faint hot WD despite the
brightness of its red companion. Visual examination shows no clear evidence of
a WD in any of the spectra. We place upper limits on the effective temperatures
of WDs that may still be hiding by fitting dM templates to the spectra, and
modeling WD spectra. On average our survey is sensitive to WDs hotter than
about 5300 K. This suggests that the frequency of WD companions of T<5300 K
with separation of order <50 AU among the local dM population is <3% at the 95%
confidence level. The reduced spectra are made available on via WISeREP
repository.
