Kavli Affiliate: Kiyoshi W. Masui
| First 5 Authors: Alexandra M. Moroianu, Alexandra M. Moroianu, , ,
| Summary:
We report the milliarcsecond localization of a high (1379 pc/cc) dispersion
measure (DM) repeating fast radio burst, 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, analogous to the
hosts of FRBs 20121102A, 20190520B and 20240114A. We also show that FRB
20190417A is spatially coincident with a compact, luminous persistent radio
source (PRS). Visibility-domain model fitting constrains the transverse
physical size of the PRS to < 23.1 pc and yields an integrated flux density of
191(39) microJy 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) and +5061(24) rad/m2 over three years. 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 1212.0 pc/cc
(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. We explore the role of these systems in the
broader FRB population, either as the youngest or most extreme FRB sources, or
as a distinct engine for FRB emission.
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