A Synoptic VLBI Technique for Localizing Non-Repeating Fast Radio Bursts with CHIME/FRB

TL;DR

This paper presents a novel VLBI technique using CHIME/FRB for precise localization of non-repeating fast radio bursts, achieving arcsecond accuracy through synchronized, high-data-rate interferometry and in-field calibration.

Contribution

It introduces a synoptic VLBI method with synchronized CHIME telescopes for blind FRB detection and localization, demonstrating high-precision results and addressing key technical challenges.

Findings

Successful detection and localization of two FRBs with 2- and 25-arcsecond precision

Implementation of high-data-rate buffering and real-time triggering system

Calibration using in-field pulsar observations to reduce systematic errors

Abstract

We demonstrate the blind interferometric detection and localization of two fast radio bursts (FRBs) with 2- and 25-arcsecond precision on the 400-m baseline between the Canadian Hydrogen Intensity Mapping Experiment (CHIME) and the CHIME Pathfinder. In the same spirit as very long baseline interferometry (VLBI), the telescopes were synchronized to separate clocks, and the channelized voltage (herein referred to as "baseband") data were saved to disk with correlation performed offline. The simultaneous wide field of view and high sensitivity required for blind FRB searches implies a high data rate -- 6.5 terabits per second (Tb/s) for CHIME and 0.8 Tb/s for the Pathfinder. Since such high data rates cannot be continuously saved, we buffer data from both telescopes locally in memory for $\approx 40$ s, and write to disk upon receipt of a low-latency trigger from the CHIME Fast Radio Burst Instrument (CHIME/FRB). The $\approx200$ deg$^2$ field of view of the two telescopes allows us to use in-field calibrators to synchronize the two telescopes without needing either separate calibrator observations or an atomic timing standard. In addition to our FRB observations, we analyze bright single pulses from the pulsars B0329+54 and B0355+54 to characterize systematic localization errors. Our results demonstrate the successful implementation of key software, triggering, and calibration challenges for CHIME/FRB Outriggers: cylindrical VLBI outrigger telescopes which, along with the CHIME telescope, will localize thousands of single FRB events to 50 milliarcsecond precision.