Open AccessCCD photometry of the globular cluster M2: RR Lyrae physical parameters and new variables
Author(s) -
Lázaro C.,
Ferro A. Arellano,
Arévalo M. J.,
Bramich D. M.,
Giridhar S.,
Poretti E.
Publication year - 2006
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2006.10742.x
Subject(s) - rr lyrae variable , physics , globular cluster , astrophysics , photometry (optics) , metallicity , ephemeris , stars , light curve , horizontal branch , variable star , luminosity , astronomy , galaxy , satellite
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 ⊙ and M V = 0.71 from nine RRab and [Fe/H]=−1.61, M = 0.54 M ⊙ , T eff = 7215 K, log L = 1.74 L ⊙ 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 ⊙ , 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.