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 , NGC 6624 , M15 , and M22 [5, 25]. 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 [211, 213]. 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 [210, 212, 216, 214, 5].
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 [59, 87, 133, 134, 50] from the accretion disk. This technique has resulted in the discovery of candidate CVs in 47 Tuc [59, 133], M92 , NGC 2808 , NGC 6397 [36, 56, 228], 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 [234, 237]. There have been 10 identified candidate CVs in 6752 , 19 in 6440 , 2 in Cen , 5 in Terzan 5 , 22 in 47 Tuc , 5 in M80 , 7 in M54 , 2–5 in NGC 288 , 4 in M30 , 4 in NGC 2808 , and 1 in M4 .Update However, some of the more energetic sources may be LMXBs in quiescence , or even candidate QSO sources .
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.
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