Hunting FRBs at high energy with AGILE

**Introduction:**

What are Fast Radio Bursts (FRBs)? These millisecond bursts from distant galaxies have astrophysicists intrigued. We explore repeating FRBs (R-FRBs) and theories about their origins, including magnetars.

**AGILE's High-Energy Hunt:**

The Italian AGILE satellite, with its SuperAGILE (18-60 keV), MCAL (0.35-100 MeV), and GRID (0.03-50 GeV) detectors, searched for X- and gamma-ray counterparts to a sample of R-FRBs.

**The Search and Non-Detection:**

AGILE observed several bursts from R-FRBs with low dispersion measure (DMexc < 300 pc cm−3). However, no astrophysical signals were identified in the X- and gamma-ray bands.

**Upper Limits and Magnetar Models:**

The study derived upper limits on the flux, particularly with MCAL, which are now the most stringent in the 0.4-30 MeV range. Researchers compared these findings to the galactic magnetar SGR 1935+2154 (the source of FRB 200428) to test magnetar emission models for FRBs.

**Key Findings:**

* **No high-energy counterparts were detected by AGILE for the observed R-FRB sample**.

* **Stringent upper limits were placed on high-energy emission**, especially by MCAL.

* The study compared R-FRB energies with those extrapolated from **SGR 1935+2154**, providing constraints on the magnetar model.

**Conclusion:**

While AGILE didn't detect high-energy counterparts for this R-FRB sample, its observations provide valuable constraints for theoretical models, especially those involving magnetars. The archival AGILE data still holds potential for future discoveries.

**Reference:**

Casentini, C., Verrecchia, F., Tavani, M., Pilia, M., & Pacciani, L. (2025). AGILE observations of a sample of repeating Fast Radio Burst sources. *Draft version March 13, 2025*.

Acknowledements: Podcast prepared with Google/NotebookLM. Illustration credits: AGILE collaboration