A new likely pulsar binary in 47 Tucanae from continuum searches

Authors

• Thomas Maccarone, Texas Tech University
• Alessandro Paduano, Curtin University
• Arash Bahramian, Curtin University
• Liliana E. Rivera Sandoval, The University of Texas Rio Grande ValleyFollow
• Jay Strader
• James C. A. Miller-Jones
• Angiraben D. Mahida
• Craig O. Heinke
• Laura Chomiuk

Document Type

Article

Publication Date

7-28-2026

Abstract

We present evidence that the X-ray source 47 Tuc W41, long considered to be an X-ray source powered by coronal activity, is actually a redback pulsar binary. The source continually shows LX = 3 × 10³¹ erg s⁻¹ (0.5–10 keV), which is well in excess of the coronal saturation limit for active binaries in quiescence, but is consistent with the intrabinary shock observed in redback pulsars, as is its photon index of Γ = 1.4 ± 0.1. In addition, using deep data from the Australia Telescope Compact Array, we show that W41 is a faint (9.8 ± 1.4μJy at 5.5 GHz) steep spectrum (α = −1.8 ± 0.4) radio continuum source, as expected for a pulsar. Light curve modelling of Hubble Space Telescope photometry shows evidence for ellipsoidal modulation with mild irradiation of a ∼ 0.5–0.55M⊙ secondary around an invisible companion, also consistent with the redback interpretation. The precise position of W41, along with its well-measured https://doi.org/10.4-hr orbital period, should enable it to be matched to a newly-discovered radio pulsar in future data. Our result shows that close pulsar binaries are still hiding, misclassified among active binaries, even in well-studied clusters like 47 Tuc.

Comments

This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution and reproduction, provided the original article is properly cited.

Recommended Citation

Maccarone, Thomas, Alessandro Paduano, Arash Bahramian, et al. “A New Likely Pulsar Binary in 47 Tucanae from Continuum Searches.” Publications of the Astronomical Society of Australia 43 (2026): e101. https://doi.org/10.1017/pasa.2026.10239.

Creative Commons License

This work is licensed under a Creative Commons Attribution 4.0 International License.

Publication Title

Publications of the Astronomical Society of Australia

DOI

https://doi.org/10.1017/pasa.2026.10239