VVV Survey of Blue Horizontal-Branch Stars in the Bulge-Halo Transition Region of the Milky Way

Abstract

We characterize the population of blue horizontal-branch (BHB) stars in the bulge-halo transition region of the Milky Way using the VISTA Variables in the Vía Láctea (VVV) ESO Public Survey data. The selection of BHB stars is made using the globular cluster M22 as a reference standard, and constructing color-magnitude and color-color diagrams with specific cuts in the $ZYJH{K}_s$ near-infrared (IR) passbands. A total of 12,554 BHB stars were detected, in a region within $-10.0^{\circ }\le \ell \le 10.2^{\circ }$ and $-10.2^{\circ }\le b\le -8.0^{\circ }$. We provide accurate coordinates and near-IR photometry for this sample of BHB stars. We searched for over-densities of stars with sizes similar to those of known globular clusters and stellar streams. By comparing real data with Monte Carlo simulations, we conclude that the few over-densities detected are of low significance. We also constructed $K_s$-band light curves for the BHB stars to study their variability. Taking an average of 52 epochs to calculate periods and amplitudes, we identify hundreds of candidate eclipsing binaries and a dozen pulsating stars. Finally, we made some comparisons with results obtained in a previous study for RR Lyrae variable stars in this same region.

arXiv comment34 pages, 378 figures, 3 tables. Accepted for publication in Astrophysical Journal

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Cited by in corpus (5)

• Discovery of new globular clusters in the Sagittarius dwarf galaxy
• Clean catalogues of blue horizontal-branch stars using Gaia EDR3
• The RR Lyrae projected density distribution from the Galactic centre to the halo
• Young stars raining through the Galactic Halo: the nature and orbit of Price-Whelan 1
• Unveiling short period binaries in the inner VVV bulge