期刊
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
卷 372, 期 1, 页码 69-80出版社
OXFORD UNIV PRESS
DOI: 10.1111/j.1365-2966.2006.10742.x
关键词
stars : horizontal branch; stars : Population II; stars : variables : other; globular clusters : individual : M2
We report the results of CCD V and R photometry of the RR Lyrae stars in M2. The periodicities of most variables are revised and new ephemerides are calculated. Light-curve decomposition of the RR Lyrae stars was carried out and the corresponding mean physical parameters [Fe/H] = -1.47, T-eff = 6276 K, log L = 1.63 L-circle dot and M-V = 0.71 from nine RRab and [Fe/H] = -1.61, M = 0.54 M-circle dot, T-eff= 7215 K, log L = 1.74 L-circle dot and M-V = 0.71 from two RRc stars were calculated. A comparison of the radii obtained from the above luminosity and temperature with predicted radii from non-linear convective models is discussed. The estimated mean distance to the cluster is 10.49 +/- 0.15 kpc. These results place M2 correctly in the general globular cluster sequences for Oosterhoff type, mass, luminosity and temperature, all as a function of the metallicity. Mean relationships for M, log L/L-circle dot, T-eff and M-V as a function of [Fe/H] for a family of globular clusters are offered. These trends are consistent with evolutionary and structural notions on the horizontal branch. Eight new variables are reported.
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