# New Cataclysmic Variables and other Exotic Binaries in the Globular Cluster 47 Tucanae

## TL;DR

This study reports 22 new cataclysmic variables in 47 Tucanae, analyzes their properties, compares them with other clusters, and discusses potential millisecond pulsar companions, revealing insights into cluster dynamics and binary evolution.

## Contribution

The paper provides the largest sample of CVs in a globular cluster, combining multi-wavelength data to analyze their distribution, luminosity function, and possible pulsar companions, highlighting differences from core-collapsed clusters.

## Key findings

- 47 Tuc hosts 43 CVs, the largest sample in any globular cluster.
- CVs are more concentrated towards the cluster center than main sequence stars.
- The CV population in 47 Tuc is likely dominated by primordial and old systems.

## Abstract

We present 22 new (+3 confirmed) cataclysmic variables (CVs) in the non core-collapsed globular cluster 47 Tucanae (47 Tuc). The total number of CVs in the cluster is now 43, the largest sample in any globular cluster so far. For the identifications we used near-ultraviolet (NUV) and optical images from the Hubble Space Telescope, in combination with X-ray results from the Chandra X-ray Observatory. This allowed us to build the deepest NUV CV luminosity function of the cluster to date. We found that the CVs in 47 Tuc are more concentrated towards the cluster center than the main sequence turnoff stars. We compared our results to the CV populations of the core-collapsed globular clusters NGC 6397 and NGC 6752. We found that 47 Tuc has fewer bright CVs per unit mass than those two other clusters. That suggests that dynamical interactions in core-collapsed clusters play a major role creating new CVs. In 47 Tuc, the CV population is probably dominated by primordial and old dynamically formed systems. We estimated that the CVs in 47 Tuc have total masses of approx. 1.4 M_sun. We also found that the X-ray luminosity function of the CVs in the three clusters is bimodal. Additionally, we discuss a possible double degenerate system and an intriguing/unclassified object. Finally, we present four systems that could be millisecond pulsar companions given their X-ray and NUV/optical colors. For one of them we present very strong evidence for being an ablated companion. The other three could be CO- or He-WDs.