A high-frequency turnover in the persistent radio source of FRB20201124A

@misc{bruni2026highfrequency,
  title = {{A high-frequency turnover in the persistent radio source of FRB20201124A}},
  author = {G. Bruni and G. Gianfagna and L. Piro and A. L. Thakur and L. Nicastro and E. Palazzi and A. Rossi and S. Savaglio and A. Gardini and Y. -P. Yang and B. Zhang},
  howpublished = {arXiv},
  year = {2026},
  month = nov,
  doi = {10.48550/arxiv.2611.05694},
  eprint = {2611.05694},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2611.05694},
  note = {CC BY 4.0},
}

TY  - UNPB
TI  - A high-frequency turnover in the persistent radio source of FRB20201124A
AU  - G. Bruni
AU  - G. Gianfagna
AU  - L. Piro
AU  - A. L. Thakur
AU  - L. Nicastro
AU  - E. Palazzi
AU  - A. Rossi
AU  - S. Savaglio
AU  - A. Gardini
AU  - Y. -P. Yang
AU  - B. Zhang
PY  - 2026
DA  - 2026/11/03
PB  - arXiv
DO  - 10.48550/arxiv.2611.05694
UR  - https://arxiv.org/abs/2611.05694
AB  - Persistent radio sources (PRSs) associated with repeating fast radio bursts probe the immediate magneto-ionic environment of their engine and thereby constrain the nature and evolutionary stage of the progenitor. The persistent radio source of FRB20201124A is the most extreme in the current sample, with a spectrum that remains flat or inverted up to 22 GHz. We aim to constrain the centimetre-to-millimetre spectral energy distribution of this source and to test whether its properties are consistent with a young, rotation-powered magnetar wind nebula. We analysed archival ALMA Band 3 observations at ∼100 GHz and combined them with existing VLA measurements at 6, 15 and 22 GHz. The resulting spectrum was fitted with the Granot--Sari broken power law in the slow-cooling regime using Bayesian nested sampling. The two-parameter model yields a peak frequency ν_m = 63^+100_−33 GHz and a peak flux F_m = 28±9 μJy. This solution is consistent with theoretical expectations for a young magnetar wind nebula, which predict a peak frequency in the same range and a self-absorption frequency below ∼0.5 GHz. With its inverted spectrum extending to tens of gigahertz and the highest peak frequency among known PRSs, the source associated with FRB20201124A is the most extreme in the current sample. Its properties match those expected for a rotation-powered magnetar wind nebula, making it a strong candidate for the youngest (t≲20 yr) magnetar associated with a repeating FRB to date.
ER  -