We report on the discovery of an extended stellar halo surrounding the distant Galactic globular cluster NGC 5694 , based on new deep ( V \simeq 24.5 ) wide-field ( 24 \arcmin \times 20 \arcmin ) photometry acquired with VIMOS at VLT .
Stars with colour and magnitude consistent with the Main Sequence of the cluster are clearly identified out to r \simeq 9 \arcmin ( \simeq 93 pc ) from the cluster center , much beyond the tidal radius of the King model that best fits the inner profile ( r _ { t } = 3.15 \arcmin ) .
We do not find a clear end of the structure within our field .
The overall observed profile can not be properly fitted with either a King ( 1966 ) model , an Elson et al .
( 1987 ) model , or a Wilson ( 1975 ) model ; however it is very smooth and does not show any sign of the break near the tidal radius that is typically observed in stellar systems with tidal tails .
The density map we derived does not show evidence of tidal tails , within the considered field .
The extra-tidal component contains \simeq 3.5 % of the cluster light ( mass ) and has a surface density profile falling as \sim r ^ { -3.2 } .
The possible origin of the detected structure is discussed , as a clear-cut conclusion can not be reached with the available data .