Astron. Astrophys. 362, 953-958 (2000)

Colour-magnitude diagrams of the inner halo globular clusters NGC 5986 and NGC 6712 ^*

S. Ortolani ¹, Y. Momany ¹, B. Barbuy ², E. Bica ³ and M. Catelan <sup>**  4

1</sup> Università di Padova, Dept. di Astronomia, Vicolo dell'Osservatorio 5, 35122 Padova, Italy (ortolani, momany@pd.astro.it)
² Universidade de São Paulo, Dept. de Astronomia, CP 3386, São Paulo 01060-970, Brazil (barbuy@orion.iagusp.usp.br)
³ Universidade Federal do Rio Grande do Sul, Dept. de Astronomia, CP 15051, Porto Alegre 91501-970, Brazil (bica@if.ufrgs.br)
⁴ University of Virginia, Department of Astronomy, P.O. Box 3818, VA 22903-0818, USA (catelan@virginia.edu)

Received 19 July 2000 / Accepted 31 August 2000

Abstract

We present V and I photometry for NGC 5986 and B and V for NGC 6712. NGC 5986 has a blue extended horizontal branch, while NGC 6712 has a composite red and blue horizontal branch, where the latter extends to unusual bluer colours. Both clusters have RR Lyrae.

We derive a reddening E(B-V) 0.29 and a distance from the Sun 11.2 kpc for NGC 5986, and E(B-V) 0.33 and 7.9 kpc for NGC 6712.

Their galactocentric distances of = 5.2 and 3.6 kpc respectively, locate them in the inner halo; NGC 6712 could be considered to be located in the bulge.

NGC 6712 has z 500 pc, indicating that the cluster is crossing the disk.

We estimate metallicities of [Fe/H] = -1.6 and -1.0 respectively for NGC 5986 and NGC 6712.

Key words: stars: Hertzsprung Russell (HR) and C-M diagrams Galaxy: globular clusters: individual: NGC 5986, NGC 6712

* Observations collected at the European Southern Observatory - ESO, Chile, proposal no. 64L-0212(A)
** Hubble Fellow

Send offprint requests to: B. Barbuy

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Contents

• 1. Introduction
• 2. Observations
• 3. NGC 5986
  • 3.1. Colour-magnitude diagrams
  • 3.2. Cluster reddening and distance
  • 3.3. Variable stars
• 4. NGC 6712
  • 4.1. Colour-magnitude diagrams
  • 4.2. Cluster parameters
    • 4.2.1. Metallicity
    • 4.2.2. Cluster reddening and distance
  • 4.3. Variable stars
• 5. Conclusions
• Acknowledgements
• References

© European Southern Observatory (ESO) 2000

Online publication: October 30, 2000
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