Astron. Astrophys. 348, 783-788 (1999)

The metal-rich bulge globular cluster NGC 6401 ^*

B. Barbuy ¹, S. Ortolani ^2,3, E. Bica ⁴ and S. Desidera <sup>2

1</sup> Universidade de São Paulo, CP 3386, São Paulo 01060-970, Brazil (barbuy@orion.iagusp.usp.br)
² Università di Padova, Dept. di Astronomia, Vicolo dell'Osservatorio 5, I-35122 Padova, Italy (ortolani, desidera@pd.astro.it)
³ European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748, Garching bei München, Germany (sortolan@eso.org)
⁴ Universidade Federal do Rio Grande do Sul, Dept. de Astronomia, CP 15051, Porto Alegre 91501-970, Brazil (bica@if.ufrgs.br)

Received 29 April 1999 / Accepted 24 June 1999

Abstract

We present V and I photometry for the bulge globular cluster NGC 6401 for the first time. The Colour-Magnitude Diagram reveals a red horizontal branch, and the cluster is metal-rich ([Fe/H] -0.7). NGC 6401 is located at 5.3^o from the Galactic center, turning out to be an interesting target to trace the extent of the bulge.

A reddening E(B-V) = 0.530.15 and a distance from the Sun 12.01.0 kpc are derived. The cluster is slightly behind the bulk of the bulge population in that direction, but still within the bulge volume.

Since the number of clusters with Horizontal Branch information has increased enormously in the later years for the central 20^o20^o, we present a discussion on the distribution of red and blue horizontal branch clusters and their possible relation to bulge and/or halo.

Key words: stars: Hertzsprung Russel (HR) and C-M diagrams Galaxy: globular clusters: individual: NGC 6401

* Observations collected at the European Southern Observatory - ESO, Chile, proposal no. 61.E-0335

Send offprint requests to: B. Barbuy

This article contains no SIMBAD objects.

Contents

• 1. Introduction
• 2. Observations
• 3. NGC 6401
  • 3.1. Colour-magnitude diagrams
  • 3.2. Cluster reddening and distance
  • 3.3. Parameters for the field
• 4. Discussion and concluding remarks
• Acknowledgements
• References

© European Southern Observatory (ESO) 1999

Online publication: August 13, 199
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