NGC 6397 is, together with NGC 6121, one of the two nearest globular clusters.
In his recent compilation Djorgovski (1993) lists for it
, 
and 
.
Despite cluster closeness the central part of NGC 6397 is relatively
difficult to study because of the high surface density of stars in this
region. The cluster
supposedly went through the core-collapse episode in the past
(Djorgovski & King 1986).
Alcaino et al. (1987) published photographic photometry for the
large part of the cluster as well as CCD photometry for a relatively small
area located in an outer part of the cluster. Ground based CCD
photometry for the central part of NGC 6397 was published by Auriere
et al. (1990) and by Lauzeral et al. (1992). These
studies revealed presence of about two dozen blue stragglers in the cluster
center. More recently several groups used data obtained with the HST
to study stellar population in NGC 6397 (Burgarella et al.
1994; De Marchi & Paresce 1994; Cool et al.
1995; King et al. 1995).
Very few variable stars are known in NGC 6397. The cluster shows a very blue horizontal branch which is void of any RR Lyr pulsators. Hogg (1973) catalogue lists two long period variables belonging to the cluster and one background RR Lyr star. Rubenstein & Bailyn (1993) reported a discovery of 5 SX Phe variables among NGC 6397 blue stragglers. Published light curves of these candidate variables are very noisy and show full amplitudes ranging from a few hundredths of magnitude to 0.15 magnitude. The quoted report had a rather preliminary character and no further details were published so far.
In this contribution we presents results of a mini-survey for short period variables located in the central part of NGC 6397.