Seeing the trees through the forest

Image may be NSFW.
Clik here to view.© Ould-Boukattine & Hewitt

In a recent paper, Dense forests of microshots in bursts from FRB 20220912A (Hewitt et al. 2023, MNRAS, 526, 2039) we used a single Westerbork dish (RT1) together with its EVN baseband data recorder (DBBC) to study a hyper-active repeating fast radio burst (FRB) on (sub-)microsecond timescales. Observing in parallel with the Nançay Radio Telescope (NRT) in France, we caught some exceptionally bright bursts, including the one shown here.

This figure shows the brightness of the burst as a function of time and frequency (a dynamic spectrum). At an ultra-high time resolution of 1 microsecond, it's hard to show all the details in a single plot. To solve this dynamic range problem, the top panels show zoom-ins at the times of 3 microshots (marked by different coloured bands in the bottom panel). These are the `trees' that we're seeing through the `forest' of the burst, which lasts for more than 10 milliseconds in total (1000 times longer than the individual microshots). We've used these high-quality data to argue that FRB sources might produce multiple emission types at once: narrow but broadband microshots, which can be clustered in time into `forests', plus wider sub-bursts that are narrow-band and drift to later times.