The CMD's of all monitored fields contain sizeable population of candidates for blue stragglers. Blue stragglers are known to be present in most well studied globular clusters (e.g. Ferraro et al. 1995). Several lines of evidence indicate that blue stragglers have higher masses than turnoff stars in their parent clusters. This supports hypothesis, originally proposed by McCrea (1964) that they are formed by merging of close binaries. In fact a few dozen photometric binary blue stragglers were discovered in globular clusters during recent years (see Mateo 1996 for a recent summary). These are mostly W UMa-type contact systems but some detached and semi-detached systems are also known. Another type of variable blue stragglers occurring in globulars are SX Phe stars. The fraction of variables seems to vary significantly from cluster to cluster. For example about 30% of blue stragglers in NGC 5053 are short-period variables (Nemec et al. 1995) while no single variable could be identified among 27 blue stragglers in NGC 6366 (Harris 1993). It is not clear for the moment how the relative frequency of variable blue stragglers correlates with such parameters as age and metallicity of a host cluster.
We used our data to estimate a relative frequency of contact binaries
and SX Phe stars among 
Cen blue stragglers. It has to be noted
at this point that the definition of blue stragglers is somehow
flexible. It is unclear how to separate regions occupied by the turnoff
stars and faint blue stragglers.
For fields 5139A, 5139BC, 5139C and 5139D the following limits are adopted
to define area occupied by blue stragglers: 16<V<18, 0.30<V-I<0.70.
For fields 5139E and 5139F the corresponding limits are: 16<V<18,
0.30<V-I<0.75. The different definition of the red edge of the
blue stragglers area reflects differences in the turnoff color
observed for monitored fields. These differences may be possibly caused by
the patchy reddening across the cluster face.
The data presented in Fig. 8 (click here) and the data presented in Fig. 12 from
Paper I were used to determine a number of blue stragglers in each of
monitored fields. Note that presented CMD's are incomplete as we
plotted only stars with relatively reliable photometry. The degree of
incompleteness varies with changing crowding.
Table 8 (click here) gives a number of selected blue stragglers candidates.
Only objects whose light curves were analyzed for variability
were retained in this statistic. The number of variable blue
stragglers which were included in presented CMD's is also given
in Table 8 (click here). All counted objects are blue stragglers according
to adopted criteria on color and magnitude
. Note that some detected variable blue stragglers were dropped from
the statistic. These were stars with formally poor photometry
in the data sets used for plotting the CMD's.
The fields 5139A and 5139C-F overlap with field 5139BC. Moreover, field
5139F overlaps with fields 5130E and 5139C.
The statistics given in Table 8 (click here) applies to the non-overlapping
parts of surveyed fields. The effective area of all fields are given in
the second column of Table 8 (click here).
We counted a total of 200 candidate blue stragglers. This number
includes 24 SX Phe stars and 11 binaries (9 EW and 2 EB/EA systems).
We showed that most of detected variables are very likely cluster
members.
The lower limits on the relative frequency of SX Phe stars and eclipsing
binaries among cluster blue straggles are (24/200)=0.12 and
11/200=0.055, respectively.
It is difficult to asses precisely what fraction of candidate
blue stragglers are field interlopers. However, we note that
the surface density of possible blue stragglers is by a factor of
higher for the central field 5139BC than for the
outermost field 5139F. It may be concluded that most of selected blue
stragglers are indeed members of the cluster.
Our data indicate that 
Cen contains the largest number of blue
stragglers among all well studied galactic globular clusters (e.g.
Ferraro et al. 1995).
Table 8:
Number of blue straggler candidates and number of
variable blue stragglers in 6 
Cen fields.
The second column gives relative area of a given field in units
of area of the field 5139BC.
N(SX) and N(ecl) denote numbers of SX Phe stars and eclipsing
binaries, respectively. The last row summarizes data for all fields