  Context. Observations of cataclysmic variables in globular clusters appear to
show a dearth of outbursts compared to those observed in the field. A number of
explanations have been proposed, including low mass-transfer rates and/or
moderate magnetic fields implying higher mass white dwarfs than the average
observed in the field. Alternatively this apparent dearth may be simply a
selection bias. Aims. We examine multi-wavelength data of a new cataclysmic
variable, CV1, in the globular cluster M 22 to try to constrain its period and
magnetic nature, with an aim at understanding whether globular cluster
cataclysmic variables are intrinsically different from those observed in the
field. Methods. We use the sub-arcsecond resolution of the Chandra ACIS-S to
identify the X-ray counterpart to CV1 and analyse the X-ray spectrum to
determine the spectral model that best describes this source. We also examine
the low resolution optical spectrum for emission lines typical of cataclysmic
variables. Cross correlating the Halpha line in each individual spectrum also
allows us to search for orbital motion. Results. The X-ray spectrum reveals a
source best-fitted with a high-temperature bremsstrahlung model and an X-ray
unabsorbed luminosity of 1.8e32 erg/s (0.3-8.0 keV), which are typical of
cataclysmic variables. Optical spectra reveal Balmer emission lines, which are
indicative of an accretion disc. Potential radial velocity in the Halpha
emission line is detected and a period for CV1 is proposed. Conclusions. These
observations support the CV identification. The radial velocity measurements
suggest that CV1 may have an orbital period of ~7 hours, but further higher
resolution optical spectroscopy of CV1 is needed to unequivocally establish the
nature of this CV and its orbital period.
