The metal-rich bulge globular cluster NGC 6401

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 metalrich ([Fe/H] ≈ -0.7). NGC 6401 is located at 5.3° from the Galactic center, turning out to be an interesting target to trace the extent of the bulge. A reddening E(B-V) = 0.53 ± 0.15 and a distance from the Sun dʘ ≈ 12.0 ± 1.0 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° x 20° , we present a discussion on the distribution of red and blue horizontal branch clusters and their possible relation to bulge and/or halo.