RR Lyrae stars and the horizontal branch of NGC 5904 (M5)

A. Arellano Ferro, A. Luna, D. M. Bramich, Sunetra Giridhar, J. A. Ahumada, S. Muneer

Research output: Contribution to journalArticle

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Abstract

We report the distance and [Fe/H] value for the globular cluster NGC 5904 (M5) derived from the Fourier decomposition of the light curves of selected RRab and RRc stars. The aim in doing this was to bring these parameters into the homogeneous scales established by our previous work on numerous other globular clusters, allowing a direct comparison of the horizontal branch luminosity in clusters with a wide range of metallicities. Our CCD photometry of the large variable star population of this cluster is used to discuss light curve peculiarities, like Blazhko modulations, on an individual basis. New Blazhko variables are reported. From the RRab stars we found [ Fe / H ] UVES= − 1.335 ± 0.003 (statistical) ± 0.110 (systematic) , and a distance of 7.6 ± 0.2 kpc , and from the RRc stars we found [ Fe / H ] UVES= − 1.39 ± 0.03 (statistical) ± 0.12 (systematic) and a distance of 7.5 ± 0.3 kpc. The results for RRab and RRc stars should be considered independent since they come from different calibrations and zero points. Absolute magnitudes, radii and masses are also reported for individual RR Lyrae stars. The distance to the cluster was also calculated by alternative methods like the Period-Luminosity relation of SX Phe and the luminosity of the stars at the tip of the red giant branch, and we obtained the results 7.7 ± 0.4 and 7.2–7.5 kpc respectively. The distribution of RR Lyrae stars in the instability strip is discussed and compared with other clusters in connection with the Oosterhoff and horizontal branch type. The Oosterhoff type II clusters systematically show a RRab-RRc segregation about the instability strip first-overtone red edge, while the Oosterhoff type I clusters may or may not display this feature. A group of RR Lyrae stars is identified in an advanced evolutionary stage, and two of them are likely binaries with unseen companions.

Original languageEnglish
Article number175
JournalAstrophysics and Space Science
Volume361
Issue number5
DOIs
Publication statusPublished - 1 May 2016
Externally publishedYes

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stars
luminosity
globular clusters
decomposition
light curve
calibration
strip
variable stars
metallicity
photometry
charge coupled devices
harmonics
modulation
radii
distribution
comparison
method
parameter

Keywords

  • Globular clusters: individual (NGC 5904)
  • Stars: variables: RR Lyrae, SX Phe, SR

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Arellano Ferro, A., Luna, A., Bramich, D. M., Giridhar, S., Ahumada, J. A., & Muneer, S. (2016). RR Lyrae stars and the horizontal branch of NGC 5904 (M5). Astrophysics and Space Science, 361(5), [175]. https://doi.org/10.1007/s10509-016-2757-5

RR Lyrae stars and the horizontal branch of NGC 5904 (M5). / Arellano Ferro, A.; Luna, A.; Bramich, D. M.; Giridhar, Sunetra; Ahumada, J. A.; Muneer, S.

In: Astrophysics and Space Science, Vol. 361, No. 5, 175, 01.05.2016.

Research output: Contribution to journalArticle

Arellano Ferro, A, Luna, A, Bramich, DM, Giridhar, S, Ahumada, JA & Muneer, S 2016, 'RR Lyrae stars and the horizontal branch of NGC 5904 (M5)', Astrophysics and Space Science, vol. 361, no. 5, 175. https://doi.org/10.1007/s10509-016-2757-5
Arellano Ferro, A. ; Luna, A. ; Bramich, D. M. ; Giridhar, Sunetra ; Ahumada, J. A. ; Muneer, S. / RR Lyrae stars and the horizontal branch of NGC 5904 (M5). In: Astrophysics and Space Science. 2016 ; Vol. 361, No. 5.
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AB - We report the distance and [Fe/H] value for the globular cluster NGC 5904 (M5) derived from the Fourier decomposition of the light curves of selected RRab and RRc stars. The aim in doing this was to bring these parameters into the homogeneous scales established by our previous work on numerous other globular clusters, allowing a direct comparison of the horizontal branch luminosity in clusters with a wide range of metallicities. Our CCD photometry of the large variable star population of this cluster is used to discuss light curve peculiarities, like Blazhko modulations, on an individual basis. New Blazhko variables are reported. From the RRab stars we found [ Fe / H ] UVES= − 1.335 ± 0.003 (statistical) ± 0.110 (systematic) , and a distance of 7.6 ± 0.2 kpc , and from the RRc stars we found [ Fe / H ] UVES= − 1.39 ± 0.03 (statistical) ± 0.12 (systematic) and a distance of 7.5 ± 0.3 kpc. The results for RRab and RRc stars should be considered independent since they come from different calibrations and zero points. Absolute magnitudes, radii and masses are also reported for individual RR Lyrae stars. The distance to the cluster was also calculated by alternative methods like the Period-Luminosity relation of SX Phe and the luminosity of the stars at the tip of the red giant branch, and we obtained the results 7.7 ± 0.4 and 7.2–7.5 kpc respectively. The distribution of RR Lyrae stars in the instability strip is discussed and compared with other clusters in connection with the Oosterhoff and horizontal branch type. The Oosterhoff type II clusters systematically show a RRab-RRc segregation about the instability strip first-overtone red edge, while the Oosterhoff type I clusters may or may not display this feature. A group of RR Lyrae stars is identified in an advanced evolutionary stage, and two of them are likely binaries with unseen companions.

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