Accretion onto the white dwarf may eventually lead to a dwarf nova outburst. Identifications of globular cluster CVs have been made through such outbursts in the cores of M5 , 47 Tuc , and NGC 6624 . With the exception of V101 in M5 , original searches for dwarf novae performed with ground based telescopes proved unsuccessful. This is primarily due to the fact that crowding obscured potential dwarf novae up to several core radii outside the center of the cluster [145, 147]. Since binaries tend to settle into the core, it is not surprising that none were found significantly outside of the core. Subsequent searches using the improved resolution of the Hubble Space Telescope eventually revealed a few dwarf novae close to the cores of selected globular clusters [144, 146, 148].
A more productive approach has been to look for direct evidence of the accretion around the white dwarf. This can be in the form of excess UV emission and strong emission [44, 63, 93] from the accretion disk. This technique has resulted in the discovery of candidate CVs in 47 Tuc [44, 93], M92 , NGC 6397 [26, 41, 156], and NGC 6712 . The accretion disk can also be discerned by very soft X-ray emissions. These low luminosity X-ray binaries are characterized by a luminosity , which distinguishes them from the low-mass X-ray binaries with . Initial explanations of these objects focused on accreting white dwarfs , and a significant fraction of them are probably CVs. However, some of the more energetic sources may be LMXBs in quiescence.
Early searches performed with ROSAT data (which had a detection limit of ) revealed roughly 30 sources in 19 globular clusters . A more recent census of the ROSAT low luminosity X-ray sources, published by Verbunt , lists 26 such sources that are probably related to globular clusters. Recent observations with the improved angular resolution of Chandra have begun to uncover numerous low luminosity X-ray candidates for CVs [64, 65, 73, 79]. An attempt to identify an IR counterpart to the LMXB X-ray burster in Liller 1 with Chandra also resulted in the serendipitous discovery of 3 low luminosity X-ray sources , which may be quiescent LMXBs. Another probable quiescent LMXB has been observed in NGC 5139 with Chandra . Observations of NGC 6652 have also discovered 3 new low luminosity X-ray sources, two of which may be CVs . The most comprehensive survey of X-ray sources in a globular cluster is that of Grindlay et al. , which presents results of high resolution Chandra images of 47 Tuc. In addition to numerous other X-ray sources, they report 13 candidate CVs.
The state of the field at this time is one of rapid change as Chandra results come in and optical counterparts are found for the new X-ray sources. A living catalog of CVs has been created by Downes et al.  and may be the best source for confirmed CVs in globular clusters.