A multi-wavelength survey of NGC\,6752: X-ray counterparts, two new dwarf novae, and a core-collapsed radial profile

TL;DR

This multi-wavelength survey of NGC 6752 identified new dwarf novae, optical counterparts to X-ray sources, and revealed a core-collapsed profile with various stellar populations, enhancing understanding of cluster dynamics and binary systems.

Contribution

The study provides new identifications of dwarf novae and X-ray counterparts, and demonstrates the cluster's core-collapsed state through detailed density profile analysis.

Findings

Confirmed two dwarf novae undergoing outbursts.

Identified optical counterparts to two X-ray sources.

Cluster exhibits a core-collapsed or post-core collapse profile.

Abstract

We present the results of a multi-wavelength (FUV to I-band) survey of the stellar populations of the globular cluster NGC 6752, using STIS, ACS and WFC3 on board the Hubble Space Telescope. We have confirmed that two previously identified CV candidates are, in fact, dwarf novae which underwent outbursts during our observations. We have also identified previously unknown optical counterparts to two X-ray sources. We estimate the position of the centre of the cluster, and show that the stellar density profile is not well described by a single King model, indicating that this cluster is in a core-collapsed or post-core collapse phase. The colour-magnitude diagram shows a well-populated horizontal branch, numerous blue stragglers and white dwarfs (WDs), as well as 87 sources in the gap region where we expect to find WD - main sequence binaries, including cataclysmic variables (CVs). The X-ray sources and WD binary systems are the most centrally concentrated populations, with dynamically estimated characteristic masses >1.1Msun and >0.8Msun, respectively.