Stellar Exotica in 47 Tucanae
Christian Knigge (1), Andrea Dieball (1), Jesus Maiz Apellaniz (2),, Knox S. Long (3), David R. Zurek (4), Michael M. Shara (4) ((1) University of, Southampton, (2) IAA-CSIC, (3) STSCI, (4) AMNH)

TL;DR
This study uses HST far-UV spectroscopy to identify and analyze exotic stellar objects in 47 Tucanae's core, revealing new types and confirming known objects, highlighting the cluster's complex stellar dynamics.
Contribution
The paper provides the first spectroscopic confirmation of CVs, discovers new exotic objects including a BS-WD binary, and estimates the binary fraction in 47 Tuc's core.
Findings
Confirmed 3 CVs and found evidence for dwarf nova eruptions.
Discovered a hot, low-mass secondary star likely from a recent dynamical encounter.
Identified a Helium WD and a BS-WD binary, first in a globular cluster.
Abstract
We present far-UV spectroscopy obtained with HST for 48 blue objects in the core of 47 Tuc. Based on their position in a FUV-optical colour-magnitude diagram, these were expected to include cataclysmic variables (CVs), blue stragglers (BSs), white dwarfs (WDs) and other exotic objects. For a subset of these sources, we also construct FUV-NIR SEDs. Based on our analysis of this extensive data set, we report the following main results. (1) We spectroscopically confirm 3 previously known or suspected CVs via the detection of emission lines and find new evidence for dwarf nova eruptions in two of these. (2) Only one other source in our spectroscopic sample exhibits marginal evidence for line emission, but predicted and observed CV numbers still agree to within a factor of about 2-3. (3) We have discovered a hot (T_eff = 8700 K), low-mass (M = 0.05 M_sun) secondary star in a previously known…
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