CCD photometry of the globular cluster M2: RR Lyrae physical parameters and new variables

  1. C. Lázaro1,2,*,
  2. A. Arellano Ferro3,*,
  3. M. J. Arévalo1,2,*,
  4. D. M. Bramich4,
  5. S. Giridhar5,
  6. E. Poretti6

Article first published online: 7 SEP 2006

DOI: 10.1111/j.1365-2966.2006.10742.x

Issue

Monthly Notices of the Royal Astronomical Society

Monthly Notices of the Royal Astronomical Society

Volume 372, Issue 1, pages 69–80, October 2006

Additional Information

How to Cite

Lázaro, C., Ferro, A. A., Arévalo, M. J., Bramich, D. M., Giridhar, S. and Poretti, E. (2006), CCD photometry of the globular cluster M2: RR Lyrae physical parameters and new variables. Monthly Notices of the Royal Astronomical Society, 372: 69–80. doi: 10.1111/j.1365-2966.2006.10742.x

Author Information

  1. 1

    Departamento de Astrofísica, Universidad de La Laguna, La Laguna, Tenerife, Spain

  2. 2

    Instituto de Astrofísica de Canarias, La Laguna, Tenerife, Spain

  3. 3

    Instituto de Astronomía, Universidad Nacional Autónoma de México, DF, Mexico

  4. 4

    Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA

  5. 5

    Indian Institute of Astrophysics, Koramangala 560034, Bangalore, India

  6. 6

    INAF–Osservatorio Astronomico di Brera, via E. Bianchi 46, I-23807 Merate, Italy

* E-mail: clh@ll.iac.es (CL); armando@astroscu.unam.mx (AAF); mam@iac.es (MJA)

Publication History

  1. Issue published online: 7 SEP 2006
  2. Article first published online: 7 SEP 2006
  3. Accepted 2006 June 27. Received 2006 June 27; in original form 2006 March 2

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Keywords:

  • stars: horizontal branch;
  • stars: Population II;
  • stars: variables: other;
  • globular clusters: individual: M2.

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, 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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