Published October 10, 2025 | Version Published
Journal Article Open

Thermal Electrons in the Radio Afterglow of Relativistic Tidal Disruption Event ZTF22aaajecp/AT 2022cmc

  • 1. Trottier Space Institute at McGill, 3550 Rue University, Montreal, QC H3A 2A7, Canada
  • 2. ROR icon McGill University
  • 3. ROR icon University of Minnesota
  • 4. ROR icon University of Oxford
  • 5. ROR icon University of Cape Town
  • 6. ROR icon University of Cambridge
  • 7. ROR icon Hebrew University of Jerusalem
  • 8. ROR icon George Washington University
  • 9. ROR icon Indian Institute of Technology Kanpur
  • 10. ROR icon California Institute of Technology
  • 11. ROR icon University of California, Berkeley
  • 12. ROR icon University of Manchester

Abstract

A tidal disruption event (TDE) occurs when a star travels too close to a supermassive black hole. In some cases, accretion of the disrupted material onto the black hole launches a relativistic jet. In this paper, we present a long-term observing campaign to study the radio and submillimeter emission associated with the fifth jetted/relativistic TDE: AT 2022cmc. Our campaign reveals a long-lived counterpart. We fit three different models to our data: a nonthermal jet, a spherical outflow consisting of both thermal and nonthermal electrons, and a jet with thermal and nonthermal electrons. We find that the data are best described by a relativistic spherical outflow propagating into an environment with a density profile following R−1.8. Comparison of AT 2022cmc to other TDEs finds agreement in the density profile of the environment but also that AT 2022cmc is twice as energetic as the other well-studied relativistic TDE, Swift J1644. Our observations of AT 2022cmc allow a thermal electron population to be inferred for the first time in a jetted transient, providing new insights into the microphysics of relativistic transients jets.

Copyright and License

© 2025. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.

Acknowledgement

L.R. acknowledges support from the Trottier Space Institute Fellowship and the Canada Excellence Research Chair in Transient Astrophysics (CERC-2022-00009). L.R. thanks Adelle Goodwin for contributing to Figures 5 and 6. R.P.F. acknowledges support from UKRI, the ERC, and the Hintze Family Charitable Foundation. A.H. is grateful for the support by the Israel Science Foundation (ISF grant 1679/23) and by the United States–Israel Binational Science Foundation (BSF grant 2020203). This research was supported in part by grant NSF PHY-2309135 to the Kavli Institute for Theoretical Physics (KITP). D.H. acknowledges funding from the NSERC Arthur B. McDonald Fellowship and Discovery Grant programs and the Canada Research Chairs (CRC) program. The authors acknowledge support from the Centre de recherche en astrophysique du Québec, un regroupement stratégique du FRQNT.

e-MERLIN is a National Facility operated by the University of Manchester at Jodrell Bank Observatory on behalf of STFC. This project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No. 101004719. We thank the staff at the Mullard Radio Astronomy Observatory for carrying out observations with the Arcminute Microkelvin Imager–Large Array.

Facilities

AMI - Arcminute MicroKelvin Imager, MERLIN - Multi-Element Radio-Linked Interferometer Network Array, MeerKAT - , IRAM:NOEMA - .

Software References

python.

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Additional details

Related works

Is new version of
Discussion Paper: arXiv:2506.13618 (arXiv)

Funding

Trottier Family Foundation
Canada Excellence Research Chairs
CERC-2022-00009
UK Research and Innovation
European Research Council
Hintze Family Charitable Foundation
Israel Science Foundation
1679/23
United States-Israel Binational Science Foundation
2020203
National Science Foundation
PHY-2309135
Natural Sciences and Engineering Research Council
Canada Research Chairs
European Union
101004719

Dates

Accepted
2025-09-03

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