CaltechAUTHORS
Published January 1, 2026 | Version Published
Journal Article Open

A Milliarcsecond Localization Associates FRB 20190417A with a Compact Persistent Radio Source and an Extreme Magnetoionic Environment

Creators

  • 1. ROR icon University of Amsterdam
  • 2. SKA Observatory (SKAO), Science Operations Centre, CSIRO ARRC, Kensington WA 6151, Australia
  • 3. ROR icon University of Toronto
  • 4. ROR icon McGill University
  • 5. ROR icon Netherlands Institute for Radio Astronomy
  • 6. ROR icon Chalmers University of Technology
  • 7. ROR icon Joint Institute for VLBI in Europe
  • 8. ROR icon Stanford University
  • 9. ROR icon Max Planck Institute for Radio Astronomy
  • 10. ROR icon University of Manchester
  • 11. ROR icon University of Bristol
  • 12. ROR icon Ventspils University College
  • 13. ROR icon Osservatorio Astrofisico di Catania
  • 14. ROR icon Istituto di Radioastronomia di Bologna
  • 15. ROR icon Cornell University
  • 16. INAF—Osservatorio Astronomico di Cagliari, via della Scienza 5, I-09047, Selargius (CA), Italy
  • 17. ROR icon Nicolaus Copernicus University
  • 18. ROR icon University of California, Santa Cruz
  • 19. ROR icon University of California, Berkeley
  • 20. ROR icon Massachusetts Institute of Technology
  • 21. ROR icon Laboratoire d'Astrophysique de Marseille
  • 22. ROR icon York University
  • 23. ROR icon California Institute of Technology

Abstract

We report the milliarcsecond localization of a high (∼1379 pc cm−3) dispersion measure (DM) repeating fast radio burst (FRB), FRB 20190417A. Combining European VLBI Network detections of five repeat bursts, we confirm the FRB’s host to be a low-metallicity, star-forming dwarf galaxy at z = 0.12817, similar to the hosts of FRB 20121102A, FRB 20190520B, and FRB 20240114A. We also confirm that it is associated with a previously reported persistent radio source (PRS), which is compact on milliarcsecond scales. Visibility-domain model fitting constrains the transverse physical size of the PRS to <23 pc and yields an integrated flux density of 190 ± 40 μJy at 1.4 GHz. Though we do not find significant evidence for DM evolution, FRB 20190417A exhibits a time-variable rotation measure (RM) ranging between +3958 ± 11 rad m−2 and +5061 ± 24 rad m−2 over a 50-day period. We find no evidence for intervening galaxy clusters in the FRB’s line of sight and place a conservative lower limit on the rest-frame host DM contribution of 1228 pc cm−3 (90% confidence)—the largest known for any FRB so far. This system strengthens the emerging picture of a rare subclass of repeating FRBs with large and variable RMs, above-average host DMs, and luminous PRS counterparts in metal-poor dwarf galaxies. Our results suggest that these systems are the result of environmental selection, or a distinct engine for FRB emission.

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

The European VLBI Network is a joint facility of independent European, African, Asian, and North American radio astronomy institutes. Scientific results from data presented in this publication are derived from the following EVN project codes: EK050 and EK051. We thank the directors and staff of the participating telescopes for allowing us to observe with their facilities. This work is based in part on observations carried out using the 32 m radio telescope operated by the Institute of Astronomy of the Nicolaus Copernicus University in Toruń (Poland) and supported by a Polish Ministry of Science and Higher Education SpUB grant. S.B. is supported by a Dutch Research Council (NWO) Veni Fellowship (VI.Veni.212.058). M.R.D. acknowledges support from the NSERC through grant No. RGPIN-2019-06186, the Canada Research Chairs Program, the Canadian Institute for Advanced Research (CIFAR), and the Dunlap Institute at the University of Toronto. The AstroFlash research group at McGill University, University of Amsterdam, ASTRON, and JIVE acknowledges support from a Canada Excellence Research Chair in Transient Astrophysics (CERC-2022-00009), an Advanced Grant from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (“EuroFlash”; grant agreement No. 101098079), and an NWO-Vici grant (“AstroFlash”; VI.C.192.045). B.M. acknowledges financial support from the State Agency for Research of the Spanish Ministry of Science and Innovation and FEDER, UE, under grant PID2022-136828NB-C41/MICIU/AEI/10.13039/501100011033, and through the Unit of Excellence María de Maeztu 2020–2023 award to the Institute of Cosmos Sciences (CEX2019-000918-M). Z.P. is supported by an NWO Veni fellowship (VI.Veni.222.295). N.S. acknowledges support from the Simons Foundation (grant MP-SCMPS-00001470). F.K. acknowledges support from Onsala Space Observatory for the provisioning of its facilities/observational support. The Onsala Space Observatory national research infrastructure is funded through Swedish Research Council grant No. 2017-00648. C.L. acknowledges support from the Miller Institute for Basic Research at UC Berkeley. K.W.M. holds the Adam J. Burgasser Chair in Astrophysics and is supported by NSF grant 2018490. D.M. acknowledges support from the French government under the France 2030 investment plan, as part of the Initiative d’Excellence d’Aix-Marseille Université—A*MIDEX (AMX-23-CEI-088). K.N. is an MIT Kavli Fellow. A.P. is funded by the NSERC Canada Graduate Scholarships—Doctoral program. A.B.P. is a Banting Fellow, a McGill Space Institute (MSI) Fellow, and a Fonds de Recherche du Quebec—Nature et Technologies (FRQNT) postdoctoral fellow. P.S. acknowledges the support of an NSERC Discovery grant (RGPIN-2024-06266).

Data Availability

Uncalibrated visibilities of FRB 20190417A (both the bursts and the associated PRS) and its calibration sources can be downloaded from the JIVE/EVN archive, https://archive.jive.eu, under project codes EK050C, EK050D, EK050F, EK050G, EK051A, EK051B, and EK051D. Filterbank files, calibrated burst visibilities, dirty maps fits files, and the scripts that made Figures 1, 2, 4, and 6 can be accessed in our Zenodo reproduction package: doi:10.5281/zenodo.17582142. Due to the large file sizes, the burst baseband data (i.e., raw voltages) and calibrated continuum visibilities will be made available by the authors upon reasonable request.

Facilities

EVN - European VLBI Network.

Software References

FX Software Correlator (A. Keimpema et al. 2015), CASA (J. P. McMullin et al. 2007; CASA Team et al. 2022; I. M. van Bemmel et al. 2022), Difmap (M. C. Shepherd 1997), Astropy (Astropy Collaboration et al. 2013), Sigproc (D. R. Lorimer 2011).

Files

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Additional details

Additional titles

Alternative title
A milliarcsecond localization associates FRB 20190417A with a compact, luminous persistent radio source and an extreme magneto-ionic environment

Related works

Is new version of
Discussion Paper: arXiv:2509.05174 (arXiv)
Is supplemented by
Dataset: 10.5281/zenodo.17582142 (DOI)

Funding

Nederlandse Organisatie voor Wetenschappelijk Onderzoek
VI.Veni.212.058
Natural Sciences and Engineering Research Council of Canada
RGPIN-2019-06186
Canada Research Chairs
Canadian Institute for Advanced Research
Canada Excellence Research Chairs, Government of Canada
CERC-2022-00009
European Research Council
101098079
Nederlandse Organisatie voor Wetenschappelijk Onderzoek
VI.C.192.045
Ministerio de Ciencia, Innovación y Universidades
PID2022-136828NB-C41
Institut de Ciències del Cosmos
CEX2019-000918-M
Dutch Research Council
VI.Veni.222.295
Simons Foundation
MP-SCMPS-00001470
Swedish Research Council
2017-00648
University of California, Berkeley
Miller Institute for Basic Research -
National Science Foundation
2018490
Aix-Marseille Université
AMX-23-CEI-088
Fonds de Recherche du Québec – Nature et Technologies
Natural Sciences and Engineering Research Council of Canada
RGPIN-2024-06266

Dates

Submitted
2025-09-05
Accepted
2025-12-03
Available
2025-12-30
Published

Caltech Custom Metadata

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