CHIME/slow overview and pilot survey: A new backend to search for second-duration radio transients with the CHIME telescope

Abstract

We present an overview of CHIME/Slow, a real-time transient search backend under development to search for second-duration radio transients using the CHIME telescope, and results obtained from a pilot survey carried out using the prototype version of the search pipeline. The prototype CHIME/Slow pipeline was tested on archival data obtained in 2022 December, 2023 January, and 2023 February with a total on-sky time of 17 days with an instantaneous field of view of ~13 deg2. In this pilot survey, we detected nine bursts, one from a new nonrepeating source, FRB 20230204C, and eight from the known hyperactive repeating source FRB 20220912A. Out of these nine bursts, two bursts from the repeater were not detected by CHIME/FRB, while the nonrepeater was detected in the side-lobe of a beam in CHIME/FRB, exhibiting shorter burst width and narrower bandwidth compared to the CHIME/Slow detection. Here we report properties of the bursts, discuss the sensitivity and completeness of the current version of the CHIME/Slow pipeline, and outline future development to improve its performance. Finally, based on these results, we report the all-sky rate (95% credible region) of radio transients with burst widths between 16 ms and 5 s, fluence above 5 Jy ms, and observing frequency of 600 MHz to be between 184 and 4556 bursts sky-1 day-1.