标题： 球状星团M5中的RR Lyrae变星 显示英文标题

标题： RR Lyrae Variables in the Globular Cluster M5

摘要： 我们给出了M5球状星团中65颗RR Lyr变星的V波段CCD测光数据。 我们使用变星光变曲线的傅里叶分解方法，估计了16颗RRc型和26颗RRab型变星的基本物理参数。 测量得到的RRc型变星的质量、光度、有效温度和氦丰度的平均值分别为：${\cal M}=0.54{\cal M}_\odot$，log L = 1.69，T_{效应}= 7353 K 和 Y = 0.28。 对于RRab型变星，计算得出的绝对星等、金属丰度和有效温度的平均值分别为：M_V = 0.81，[Fe/H] = -1.23 和 T_{效率}= 6465 K。我们发现，对于给定周期的RRab型变星，其V波段振幅更依赖于金属丰度而非Oosterhoff类型。 我们发现，用傅里叶技术测量的光度零点和尺度标定存在显著问题。 由RRc型变星推导出的视距离模数等于$14.47\pm0.11$，与近期的测定结果一致。 另一方面，由RRab型变星样本（通过场星RR Lyr变星的Baade-Wesselink观测校准）得到的距离模数明显较小，等于$14.27\pm0.04$。 显示英文摘要

摘要： We present V-band CCD photometry of 65 RR Lyr variables from the globular cluster M5. We have estimated the basic physical parameters for 16 RRc stars and 26 RRab stars using a Fourier decomposition of the light curves of the variables. The mean values of mass, luminosity, effective temperature and relative helium abundance for the RRc stars are measured to be ${\cal M}=0.54{\cal M}_\odot$, log L = 1.69 T_{eff}=7353 K and Y=0.28, respectively. For the RRab variables the derived mean values of absolute magnitude, metallicity and effective temperature are: M_V=0.81, [Fe/H]=-1.23 and T_{eff}=6465 K. We find that the V amplitude of an RRab star for a given period is a function of metal abundance rather than Oosterhoff type. We find significant problems with the calibration of both the zero point and the scale of the luminosities measured with the Fourier technique. The apparent distance modulus derived from RRc stars is equal to $14.47\pm0.11$ and it is in good agreement with recent determinations. On the other hand distance modulus obtained from the sample of RRab stars (calibrated by the Baade-Wesselink observations of field RR Lyr variables) is significantly smaller and equal to $14.27\pm0.04$