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Published February 13, 2025 | Version Published
Journal Article Metadata-only

Millihertz oscillations near the innermost orbit of a supermassive black hole

Creators

  • 1. ROR icon Massachusetts Institute of Technology
  • 2. ROR icon University of Hertfordshire
  • 3. ROR icon Diego Portales University
  • 4. ROR icon Peking University
  • 5. ROR icon University of Maryland, Baltimore County
  • 6. ROR icon Goddard Space Flight Center
  • 7. ROR icon Tel Aviv University
  • 8. ROR icon University of Maryland, College Park
  • 9. ROR icon University of Cambridge
  • 10. ROR icon California Institute of Technology
  • 11. ROR icon Centro de Astrobiología
  • 12. ROR icon Newcastle University
  • 13. ROR icon Harvard-Smithsonian Center for Astrophysics
  • 14. INAF - IASF Palermo, Palermo, Italy

Abstract

Recent discoveries from time-domain surveys are defying our expectations for how matter accretes onto supermassive black holes (SMBHs). The increased rate of short-timescale, repetitive events around SMBHs, including the recently discovered quasi-periodic eruptions1, 2, 3, 4–5, are garnering further interest in stellar-mass companions around SMBHs and the progenitors to millihertz-frequency gravitational-wave events. Here we report the discovery of a highly significant millihertz quasi-periodic oscillation (QPO) in an actively accreting SMBH, 1ES 1927+654, which underwent a major optical, ultraviolet and X-ray outburst beginning in 20186,7. The QPO was detected in 2022 with a roughly 18-minute period, corresponding to coherent motion on a scale of less than 10 gravitational radii, much closer to the SMBH than typical quasi-periodic eruptions. The period decreased to 7.1 minutes over 2 years with a decelerating period evolution (P greater than zero). To our knowledge, this evolution has never been seen in SMBH QPOs or high-frequency QPOs in stellar-mass black holes. Models invoking orbital decay of a stellar-mass companion struggle to explain the period evolution without stable mass transfer to offset angular-momentum losses, and the lack of a direct analogue to stellar-mass black-hole QPOs means that many instability models cannot explain all of the observed properties of the QPO in 1ES 1927+654. Future X-ray monitoring will test these models, and if it is a stellar-mass orbiter, the Laser Interferometer Space Antenna (LISA) should detect its low-frequency gravitational-wave emission.

Copyright and License

© 2025 Springer Nature Limited.

Acknowledgement

We thank XMM-Newton principal investigator, N. Schartel, for approving the target-of-opportunity requests. M.M. thanks M. Ng for discussions regarding X-ray timing; L. Drummond for discussions about extreme-mass-ratio models; and the organizers and participants of the UCSB KITP TDE Workshop, including, but not limited to, J. Dai, G. Lodato, C. Nixon, A. Mummery, A. Franchini, I. Linial and D. Pasham for their comments, questions and discussions regarding these results. E.K. thanks A. Dittmann and D. Wilkins for discussions. R.A. was supported by NASA through the NASA Hubble Fellowship grant HST-HF2-51499.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555. A.I. acknowledges support from the Royal Society. M.G. is supported by the ‘Programa de Atracción de Talento’ of the Comunidad de Madrid, grant number 2022-5A/TIC-24235. C. Pinto is supported by PRIN MUR SEAWIND funded by NextGenerationEU. B.T. acknowledges support from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement number 950533) and from the Israel Science Foundation (grant number 1849/19). J.W. acknowledges support from the NASA FINESST Graduate Fellowship, under grant 80NSSC22K1596. This research was supported in part by grant NSF PHY-2309135 to the Kavli Institute for Theoretical Physics (KITP).

Data Availability

All the data used in this work are publicly available through XMM-SAS.

Code Availability

The spectra, light curves and code used to analyse the data and produce all figures have been made publicly available on CodeOcean and GitHub (https://github.com/memasterson/1ES1927_mHzQPO/).

Supplemental Material

Peer Review File

Additional details

Related works

Describes
Journal Article: https://rdcu.be/evnZO (ReadCube)
Is new version of
Discussion Paper: arXiv:2501.01581 (arXiv)
Is supplemented by
Software: https://github.com/memasterson/1ES1927_mHzQPO/ (URL)

Funding

National Aeronautics and Space Administration
NASA Hubble Fellowship HST-HF2-51499.001-A
Space Telescope Science Institute
National Aeronautics and Space Administration
NAS5-26555
Royal Society
Comunidad de Madrid
2022-5A/TIC-24235
European Research Council
950533
Israel Science Foundation
1849/19
National Aeronautics and Space Administration
80NSSC22K1596
National Science Foundation
PHY-2309135

Dates

Accepted
2024-11-11
Available
2025-02-05
Published

Caltech Custom Metadata

Caltech groups
Division of Physics, Mathematics and Astronomy (PMA)
Publication Status
Published