Localizing FRBs through VLBI with the Algonquin Radio Observatory 10 m Telescope

Abstract

The Canadian Hydrogen Intensity Mapping Experiment (CHIME)/FRB experiment has detected thousands of fast radio bursts (FRBs) due to its sensitivity and wide field of view; however, its low angular resolution prevents it from localizing events to their host galaxies. Very long baseline interferometry (VLBI), triggered by FRB detections from CHIME/FRB will solve the challenge of localization for non-repeating events. Using a refurbished 10 m radio dish at the Algonquin Radio Observatory located in Ontario Canada, we developed a testbed for a VLBI experiment with a theoretical λ/D ≲ 30 mas. We provide an overview of the 10 m system and describe its refurbishment, the data acquisition, and a procedure for fringe fitting that simultaneously estimates the geometric delay used for localization and the dispersive delay from the ionosphere. Using single pulses from the Crab pulsar, we validate the system and localization procedure, and analyze the clock stability between sites, which is critical for coherently delay referencing an FRB event. We find a localization of ∼200 mas is possible with the performance of the current system (single-baseline). Furthermore, for sources with insufficient signal or restricted wideband to simultaneously measure both geometric and ionospheric delays, we show that the differential ionospheric contribution between the two sites must be measured to a precision of 1 × 10−8 pc cm−3 to provide a reasonable localization from a detection in the 400–800 MHz band. Finally we show detection of an FRB observed simultaneously in the CHIME and the Algonquin 10 m telescope, the first non-repeating FRB in this long baseline. This project serves as a testbed for the forthcoming CHIME/FRB Outriggers project.

An Overview of CHIME, the Canadian Hydrogen Intensity Mapping Experiment

“…The data from CHIME are passed commensally to separate instruments that search for fast radio bursts (FRBs), monitor known pulsars visible from the site, and search at high spectral resolution for 21 cm line absorption systems. Additionally, CHIME supports very long baseline interferometry (VLBI; Cassanelli et al 2022) observations with other telescopes.…”

“…Additionally, lower-frequency observations of the 21 cm line are well suited to probing the era of reionization (Furlanetto et al 2019b) or, more ambitiously, the cosmic "dark ages" up to z 100 ( ) ~ (Furlanetto et al 2019a). The instrument described here also acts as the front end for several other systems, providing calibrated data to an FRB detector (CHIME/FRB Collaboration et al 2018), a 10-beam system that monitors all pulsars visible from Canada with up to daily cadence (CHIME/Pulsar Collaboration et al 2021), a system to search for cold clouds acting as 21 cm absorption-line systems, and a VLBI station (Cassanelli et al 2022). Among the accomplishments these new instruments have made is the discovery of half a dozen Galactic pulsars; detection of an exceptionally bright radio burst from a Galactic magnetar (CHIME/FRB Collaboration et al 2020), pointing to possible similarities of magnetars and FRBs; and publication of the first substantial catalog of FRBs (CHIME/ Pulsar Collaboration et al 2021).…”

Redshift Estimation and Constraints on Intergalactic and Interstellar Media from Dispersion and Scattering of Fast Radio Bursts

“…Only a small fraction of the current sample of FRBs has been reliably localized to host galaxies with redshifts, and while efforts are underway to provide routine high-precision localizations of a large number of FRBs with, e.g., CHIME outriggers (Leung et al 2021;Cassanelli et al 2022), DSA-2000(Hallinan et al 2019, and other facilities, it will take some time for such efforts to come to fruition.…”

BURSTT: Bustling Universe Radio Survey Telescope for Taiwan

“…studied (Li & Zhang 2020), which raises rather more questions than unraveling their mysterious origin. BURSTT will detect and localize ∼100 bright FRB per year to further distinguish their local environment, and such statistics are important to understand the population (Leung et al 2021;Mena-Parra et al 2022;Cassanelli et al 2022).…”

“…Very-Long Baseline Interferometry (VLBI) along with outrigger stations has been proposed to localize both nonrepeating and repeating FRBs (Cassanelli et al 2022). For the latter, the European VLBI Network (EVN) has localized several repeating FRBs to their hosts (Marcote et al 2020;Kirsten et al 2022).…”