CCD photometry of the globular cluster NGC 5466. RR Lyrae light-curve decomposition and the distance scale

A. Arellano Ferro, V. Rojas López, Sunetra Giridhar, D. M. Bramich

Research output: Contribution to journalArticle

24 Citations (Scopus)

Abstract

We report the results of CCD V and r photometry of the globular cluster NGC 5466. The difference image analysis technique adopted in this work has resulted in accurate time-series photometry even in crowded regions of the cluster enabling us to discover five probably semiregular variables. We present new photometry of three previously known eclipsing binaries and six SX Phe stars. The light curves of the RR Lyrae stars have been decomposed in their Fourier harmonics and their fundamental physical parameters have been estimated using semi-empirical calibrations. The zero-points of the metallicity, luminosity and temperature scales are discussed and our Fourier results are transformed accordingly. The average iron abundance and distance to the Sun derived from individual RR Lyrae stars, indicate values of [Fe/H] = -1.91 ± 0.19 and D = 16.0 ± 0.6 kpc, or a true distance modulus of 16.02 ± 0.09 mag, for the parent cluster. These values are, respectively, in the Zinn & West metallicity scale and in agreement with recent luminosity determinations for the RR Lyrae stars in the Large Magellanic Cloud. The MV-[Fe/H] relation has been recalibrated as MV = +(0.18 ± 0.03)[Fe/H] + (0.85 ± 0.05) using the mean values derived by the Fourier technique on RR Lyrae stars in a family of clusters. This equation predicts MV = 0.58 mag for [Fe/H] = -1.5, in agreement with the average absolute magnitude of RR Lyrae stars calculated from several independent methods. The M V-[Fe/H] relationship and the value of [Fe/H] have implications on the age of the globular clusters when determined from the magnitude difference between the horizontal branch and the turn-off point (HB-TO method). The above results however would not imply a change in the age of NGC 5466, of 12.5 ± 0.9 Gyr, estimated from recent isochrone fitting.

Original languageEnglish
Pages (from-to)1444-1458
Number of pages15
JournalMonthly Notices of the Royal Astronomical Society
Volume384
Issue number4
DOIs
Publication statusPublished - 1 Mar 2008
Externally publishedYes

Fingerprint

globular clusters
light curve
photometry
charge coupled devices
decomposition
stars
image analysis
time series
calibration
iron
metallicity
luminosity
temperature scales
temperature
Magellanic clouds
method
sun
harmonics
family
parameter

Keywords

  • Binaries: eclipsing
  • Globular clusters: individual: NGC 5466
  • Stars: distances
  • Stars: horizontal branch
  • Stars: variables: other

ASJC Scopus subject areas

  • Space and Planetary Science

Cite this

CCD photometry of the globular cluster NGC 5466. RR Lyrae light-curve decomposition and the distance scale. / Arellano Ferro, A.; Rojas López, V.; Giridhar, Sunetra; Bramich, D. M.

In: Monthly Notices of the Royal Astronomical Society, Vol. 384, No. 4, 01.03.2008, p. 1444-1458.

Research output: Contribution to journalArticle

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abstract = "We report the results of CCD V and r photometry of the globular cluster NGC 5466. The difference image analysis technique adopted in this work has resulted in accurate time-series photometry even in crowded regions of the cluster enabling us to discover five probably semiregular variables. We present new photometry of three previously known eclipsing binaries and six SX Phe stars. The light curves of the RR Lyrae stars have been decomposed in their Fourier harmonics and their fundamental physical parameters have been estimated using semi-empirical calibrations. The zero-points of the metallicity, luminosity and temperature scales are discussed and our Fourier results are transformed accordingly. The average iron abundance and distance to the Sun derived from individual RR Lyrae stars, indicate values of [Fe/H] = -1.91 ± 0.19 and D = 16.0 ± 0.6 kpc, or a true distance modulus of 16.02 ± 0.09 mag, for the parent cluster. These values are, respectively, in the Zinn & West metallicity scale and in agreement with recent luminosity determinations for the RR Lyrae stars in the Large Magellanic Cloud. The MV-[Fe/H] relation has been recalibrated as MV = +(0.18 ± 0.03)[Fe/H] + (0.85 ± 0.05) using the mean values derived by the Fourier technique on RR Lyrae stars in a family of clusters. This equation predicts MV = 0.58 mag for [Fe/H] = -1.5, in agreement with the average absolute magnitude of RR Lyrae stars calculated from several independent methods. The M V-[Fe/H] relationship and the value of [Fe/H] have implications on the age of the globular clusters when determined from the magnitude difference between the horizontal branch and the turn-off point (HB-TO method). The above results however would not imply a change in the age of NGC 5466, of 12.5 ± 0.9 Gyr, estimated from recent isochrone fitting.",
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T1 - CCD photometry of the globular cluster NGC 5466. RR Lyrae light-curve decomposition and the distance scale

AU - Arellano Ferro, A.

AU - Rojas López, V.

AU - Giridhar, Sunetra

AU - Bramich, D. M.

PY - 2008/3/1

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N2 - We report the results of CCD V and r photometry of the globular cluster NGC 5466. The difference image analysis technique adopted in this work has resulted in accurate time-series photometry even in crowded regions of the cluster enabling us to discover five probably semiregular variables. We present new photometry of three previously known eclipsing binaries and six SX Phe stars. The light curves of the RR Lyrae stars have been decomposed in their Fourier harmonics and their fundamental physical parameters have been estimated using semi-empirical calibrations. The zero-points of the metallicity, luminosity and temperature scales are discussed and our Fourier results are transformed accordingly. The average iron abundance and distance to the Sun derived from individual RR Lyrae stars, indicate values of [Fe/H] = -1.91 ± 0.19 and D = 16.0 ± 0.6 kpc, or a true distance modulus of 16.02 ± 0.09 mag, for the parent cluster. These values are, respectively, in the Zinn & West metallicity scale and in agreement with recent luminosity determinations for the RR Lyrae stars in the Large Magellanic Cloud. The MV-[Fe/H] relation has been recalibrated as MV = +(0.18 ± 0.03)[Fe/H] + (0.85 ± 0.05) using the mean values derived by the Fourier technique on RR Lyrae stars in a family of clusters. This equation predicts MV = 0.58 mag for [Fe/H] = -1.5, in agreement with the average absolute magnitude of RR Lyrae stars calculated from several independent methods. The M V-[Fe/H] relationship and the value of [Fe/H] have implications on the age of the globular clusters when determined from the magnitude difference between the horizontal branch and the turn-off point (HB-TO method). The above results however would not imply a change in the age of NGC 5466, of 12.5 ± 0.9 Gyr, estimated from recent isochrone fitting.

AB - We report the results of CCD V and r photometry of the globular cluster NGC 5466. The difference image analysis technique adopted in this work has resulted in accurate time-series photometry even in crowded regions of the cluster enabling us to discover five probably semiregular variables. We present new photometry of three previously known eclipsing binaries and six SX Phe stars. The light curves of the RR Lyrae stars have been decomposed in their Fourier harmonics and their fundamental physical parameters have been estimated using semi-empirical calibrations. The zero-points of the metallicity, luminosity and temperature scales are discussed and our Fourier results are transformed accordingly. The average iron abundance and distance to the Sun derived from individual RR Lyrae stars, indicate values of [Fe/H] = -1.91 ± 0.19 and D = 16.0 ± 0.6 kpc, or a true distance modulus of 16.02 ± 0.09 mag, for the parent cluster. These values are, respectively, in the Zinn & West metallicity scale and in agreement with recent luminosity determinations for the RR Lyrae stars in the Large Magellanic Cloud. The MV-[Fe/H] relation has been recalibrated as MV = +(0.18 ± 0.03)[Fe/H] + (0.85 ± 0.05) using the mean values derived by the Fourier technique on RR Lyrae stars in a family of clusters. This equation predicts MV = 0.58 mag for [Fe/H] = -1.5, in agreement with the average absolute magnitude of RR Lyrae stars calculated from several independent methods. The M V-[Fe/H] relationship and the value of [Fe/H] have implications on the age of the globular clusters when determined from the magnitude difference between the horizontal branch and the turn-off point (HB-TO method). The above results however would not imply a change in the age of NGC 5466, of 12.5 ± 0.9 Gyr, estimated from recent isochrone fitting.

KW - Binaries: eclipsing

KW - Globular clusters: individual: NGC 5466

KW - Stars: distances

KW - Stars: horizontal branch

KW - Stars: variables: other

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