We present a new time-series VI CCD photometry of the globular cluster NGC 6397, from which we obtained and analysed the light curves of 35 variables carefully identified in the cluster field. We assessed the membership of the variables with an astrometric analysis based on Gaia DR2 data. The cluster colour-magnitude diagram was differentially dereddened and cleaned of non members, which allowed us to fit isochrones for [Fe/H]$=-2.0$ dex in the range 13.0–13.5 Gyr, for a mean reddening $E(B-V)=0.19,$ and a distance of 2.5 kpc. This distance was confirmed using the period-luminosity relation for the cluster’s five SX Phoenicis variables (V10, V11, V15, V21, and V23) present among its blue stragglers, yielding $2.24\pm 0.13$ kpc. We also modelled the light curves of four eclipsing binaries (V4, V5, V7, and V8), and gave the parameters of the systems; the contact binaries V7 and V8 have distances consistent with that of the cluster. NGC 6397 appears to harbour no RR Lyrae stars, being its horizontal branch remarkably blue, much like that of its analogous cluster, M10. To match the blue tail of the horizontal branch population, models of 0.64–0.66 $M_{\odot }$ with mass loss at the RGB are required, indicating rather thin shell masses for horizontal branch stars.

我们介绍了球状星团NGC 6397的新的时间序列VI CCD光度法，从中我们获得并分析了在星团场中仔细识别的35个变量的光曲线。我们通过基于Gaia  DR2数据的天文分析评估了变量的隶属度。群集的色度图被不同程度地降低和清除了非成员，这使我们能够拟合[Fe / H]的等时线$=-2.0$ dex在13.0-13.5 Gyr范围内，平均变红 $E（乙-\mathrm{伏特}）=0.19，$距离为2.5 kpc。使用周期发光度关系，通过星团蓝色散布在星团中的五个SX Phoenicis变量（V10，V11，V15，V21和V23）确定了该距离，得出$2.24\pm 0.13$ 千次曝光出价。我们还对四个遮蔽二进制文件（V4，V5，V7和V8）的光曲线进行了建模，并给出了系统的参数。接触二进制文件V7和V8的距离与群集的距离一致。NGC 6397似乎没有RR天琴座星，它的水平分支明显为蓝色，非常类似于其类似星团M10的分支。为了匹配水平分支种群的蓝色尾巴，模型为0.64–0.66 ${\mathrm{中号}}_{\odot }$ 需要在RGB处有质量损失，这表示水平分支星的壳质量相当薄。