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Detecting intermediate-mass black holes using miniature pulsar timing arrays in globular clusters

Xian Chen1,2,*, Verónica Vázquez-Aceves2, Siyuan Chen3,4, Kejia Lee1,5,6,7, Yanjun Guo4,5, and Kuo Liu3,4

  • 1Department of Astronomy, School of Physics, Peking University, Beijing 100871, China
  • 2Kavli Institute for Astronomy and Astrophysics at Peking University, Beijing 100871, China
  • 3Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030, China
  • 4State Key Laboratory of Radio Astronomy and Technology, A20 Datun Road, Chaoyang District, Beijing 100101, China
  • 5National Astronomical Observatories, Chinese Academy of Sciences, A20 Datun Road, Chaoyang District, Beijing 100101, China
  • 6Yunnan Astronomical Observatories, Chinese Academy of Sciences, Kunming 650216, Yunnan, China
  • 7Beijing Laser Acceleration Innovation Center, Huairou, Beijing 101400, China

  • *Contact author: xian.chen@pku.edu.cn
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Phys. Rev. Research 7, 033300 – Published 29 September, 2025

DOI: https://doi.org/10.1103/nb5d-qzm8

Abstract

Theoretical models predict that intermediate-mass black holes (IMBHs) exist in globular clusters (GCs), but observational evidence remains elusive. Millisecond pulsars (MSPs), which are abundant in GCs and have served as precise probes for gravitational waves, offer a unique opportunity to detect potential IMBH binaries in GCs. Here, we consider the possibility of using multiple MSPs in a GC to form a miniature pulsar timing array (PTA), so as to take advantage of their correlated timing residuals to search for potential IMBH binaries in the same cluster. Our semianalytical calculations reveal that nearby IMBH binaries around MSPs in GCs could induce microsecond-level timing residuals. In GCs like ω Centauri and M15, favorable configurations are found that could lead to the detection of binaries with mass ratios q≳0.1 and orbital periods of a few days. We estimate that future higher-precision timing programs could achieve 100-ns sensitivity, substantially expanding the searchable parameter space and establishing mini-PTAs as powerful detectors of IMBHs.

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Phys. Rev. Research 7, 033300– Published 29 September, 2025
  • Received 14 July 2025
  • Accepted 15 September 2025
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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