Magnetars, Supernovae, and FRBs: A Delayed Connection?

In this episode, we dive into the mysterious world of Fast Radio Bursts (FRBs) and the ongoing quest to understand their origins. We discuss a systematic search for **past supernovae (SNe) and other historical optical transients** at the positions of FRB sources, exploring a leading theory that links FRBs to **magnetars**.

The study **found no statistically significant associations** within the 5σ FRB localization uncertainties between the observed CHIME-KKO or literature FRBs and optical transients, *except* for a previously identified potential optical counterpart to FRB 20180916B, named AT 2020hur. AT 2020hur, however, occurred *after* the FRB was first detected, making it inconsistent with the "past SN" progenitor model, though it remains a potential association under other theories.

**Chance Coincidences:** The probability of a chance coincidence (Pcc) between an FRB and a transient was found to be **low (Pcc < 0.1)**. It's estimated that it would take **~22,700 subarcsecond-localized FRBs** to yield one chance association, which translates to roughly **30–60 years** at the projected CHIME/FRB Outrigger detection rate. This means that any robust match found in the near future is highly likely to be a **physical association**.

**Implications of Transparency Time:** The research estimates that **5–7% of matched optical transients** (if all were SNe) are old enough to be associated with a detectable FRB, assuming the 6.4-10 year transparency timescale. More broadly, **23–30% of all cataloged SNe and 32–41% of CCSNe** are currently old enough to have detectable FRB emission.

**The Future with Rubin Observatory:** The upcoming **Vera C. Rubin Observatory (LSST)** is expected to dramatically increase the number of known SNe and the volume over which they can be detected. This will significantly **increase the rate of potential FRB-SN associations** at redshifts below z~1, where most FRBs are discovered.

**Flexible Framework:** The systematic search machinery developed for this work is publicly available and flexible, allowing it to be applied to a wide range of transient timescales, FRB localization sizes, and different optical transient populations in future searches.

**Reference Article:**

* DONG, Y., KILPATRICK, C. D., FONG, W., et al. (2025). **Searching for Historical Extragalactic Optical Transients Associated with Fast Radio Bursts**. arXiv e-prints, arXiv:2506.06420v1.

Acknowledements: Podcast prepared with Google/NotebookLM. Illustration credits: NASA - JPL/Caltech