Young Magnetars

Summary Table

Category	Progenitor	Type	Energy Mechanism	Emission Mechanism	Counterparts									References	Brief Comments
					LF Radio	HF Radio	Microwave	Terahertz	Optical/IR	X-rays	Gamma-rays	Gravitational Waves	Neutrinos
Merger/Collapse	Magnetars Born in NS-NS Mergers and WD Collapse	Repeat	Maser	Synch.	Yes, persistent	Yes, persistent	Maybe	Maybe	No	Afterglow	Yes if jet aligned	Yes	Not detectable	https://arxiv.org/pdf/1907.00016.pdf	Same mechanisms as flares, but magnetars born in mergers or collapse as opposed in to SLSNe or LGRBs.

Definitions: LF Radio (3 MHz to 3 GHz); HF Radio (3 GHz to 30 GHz); Microwave (30 to 300 GHz)

Model Description

This model considers FRBs from magnetars born in NS-NS mergers and accretion induced WD collapse. The FRBs themselves are formed by the same mechanism as that of giant flare FRB theories.

Observational Constraints

Persistent synchrotron radio emission with timescales of months to years from the nebula or on longer timescales when the merger ejecta interacts with the ISM, but is shorter than for the SLSNe/LGRBs. The accretion-induced collapse of a WD has yet to be observed but might produce a SNIa-like transient.

Using FRB 121102 to calibrate the model, the expected DM, RM and persistent radio emission is consistent with the upper limits of FRB 180924. FRBs from NS-NS magnetars distinct host galaxy and spatial offset distributions than the SLSNe/LGRB channel; we anticipate asimilar host population, although possibly different offset distribution for AIC events. It may be more difficult to detect persistent nebular radio emission from known FRB positions than in the SLSN/LGRB case because of high ejecta velocity and low ejecta mass: the emission peaks at early times and the ejecta become transparent to free-free absorption earlier. This is consistent with the non-detection of persistent emission from FRB 180924 and could explain its lower RM.