M2 (NGC7089) :: New paper available
Monthly Notices of the Royal Astronomical Society
Online Early Issue
C. Lázaro, A. Arellano Ferro, M. J. Arévalo, D. M. Bramich, S. Giridhar, E. Poretti
CCD photometry of the globular cluster M2: RR Lyrae physical parameters and new variables
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, Teff = 6276 K, log L = 1.63 L and MV = 0.71 from nine RRab and [Fe/H] = −1.61, M = 0.54 M, Teff = 7215 K, log L = 1.74 L and MV = 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, Teff and MV 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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