  We report time-series photometry for 16 variable stars located in the central
part of the globular cluster NGC 6752. The sample includes 13 newly identified
objects. The precision of our differential photometry ranges from 1 mmag at
V=14.0 to 10 mmag at V=18.0. We detected 4 low amplitude variables located on
the extended horizontal branch (EHB) of the cluster. They are candidate binary
stars harboring sdB subdwarfs. A candidate degenerate binary was detected about
2 mag below the faint end of the EHB. The star is blue and its light curve is
modulated with a period of 0.47 d. We argue that some of the identified
variable red/blue stragglers are ellipsoidal binaries harboring degenerate
stars. They have low amplitude sine-like light curves and periods from a few
hours to a few days. Spectroscopic observations of such objects may lead to the
detection of detached inactive binaries harboring stellar mass black holes or
neutron stars. No binaries of this kind are known so far in globular clusters
although their existence is expected based on the common occurrence of
accreting LMXBs and millisecond pulsars. An eclipsing SB1 type binary was
identified on the upper main sequence of the cluster. We detected variability
of optical counterparts to two X-ray sources located in the core region of NGC
6752. The already known cataclysmic variable B1=CX4 experienced a dwarf nova
type outburst. The light curve of an optical counterpart to the X-ray source
CX19 exhibited modulation with a period 0.113 d. The same periodicy was
detected in the HST-ACS data. The variable is located on the upper main
sequence of the cluster. It is an excellent candidate for a close degenerate
binary observed in quiescence.

Solar and Stellar Astrophysics