CCD photometry of the globular cluster M2

RR Lyrae physical parameters and new variables

C. Lázaro, A. Arellano Ferro, M. J. Arévalo, D. M. Bramich, S. Giridhar, E. Poretti

Research output: Contribution to journalArticle

21 Citations (Scopus)

Abstract

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 ef{ = 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.

Original languageEnglish
Pages (from-to)69-80
Number of pages12
JournalMonthly Notices of the Royal Astronomical Society
Volume372
Issue number1
DOIs
Publication statusPublished - 1 Oct 2006
Externally publishedYes

Fingerprint

globular clusters
photometry
charge coupled devices
stars
luminosity
periodicity
ephemerides
radii
temperature
decomposition
light curve
metallicity
periodic variations
trends
parameter
family
comparison
trend

Keywords

  • Globular clusters: individual: M2
  • Stars: horizontal branch
  • Stars: Population II
  • Stars: variables: other

ASJC Scopus subject areas

  • Space and Planetary Science

Cite this

CCD photometry of the globular cluster M2 : RR Lyrae physical parameters and new variables. / Lázaro, C.; Arellano Ferro, A.; Arévalo, M. J.; Bramich, D. M.; Giridhar, S.; Poretti, E.

In: Monthly Notices of the Royal Astronomical Society, Vol. 372, No. 1, 01.10.2006, p. 69-80.

Research output: Contribution to journalArticle

Lázaro, C. ; Arellano Ferro, A. ; Arévalo, M. J. ; Bramich, D. M. ; Giridhar, S. ; Poretti, E. / CCD photometry of the globular cluster M2 : RR Lyrae physical parameters and new variables. In: Monthly Notices of the Royal Astronomical Society. 2006 ; Vol. 372, No. 1. pp. 69-80.
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AB - 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 ef{ = 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.

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