Ziggy Pleunis

We have discovered PSR J2108+5055, an extremely luminous but sporadic mode-changing rotating radio transient (RRAT), with a period of 0.495 s using the Canadian Hydrogen Intensity Mapping Experiment (CHIME) Fast Radio Burst (FRB) instrument. We show that the brightest pulse from PSR J2108+5055 has a flux density of 3.1 ± 1.0 kJy, corresponding to a spectral luminosity of (7.5 ± 2.3) × 10 ²³ erg s ⁻¹ Hz ⁻¹ , assuming a dispersion-measure-derived distance of 1.6 ± 0.3 kpc. We place an upper limit on the duty cycle of PSR J2108+5055 at 0.002 and measure a surface magnetic field of 5.8 × 10 ¹¹ G, a characteristic age of 1.2 × 10 ⁷ yr, and a spindown luminosity of 2.2 × 10 ³² erg s ⁻¹ . Using a simple model based on the Green Bank North Celestial Cap (GBNCC) survey, we place an upper limit on the number of PSR J2108+5055–like sources with similar peak flux densities in the GBNCC survey area of ∼80 RRATs. We show that if PSR J2108+5055 were placed at the edge of the Local Group of galaxies, the Five-hundred-meter Aperture Spherical radio Telescope (FAST) would detect its brightest pulse. The second brightest pulse has a peak flux density of 1.5 ± 0.7 kJy, and FAST would detect such a pulse out to ∼1 Mpc, covering the inner Local Group, including Andromeda.

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 deg ² . 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 .

This paper introduces an approach to analyze nonhomogeneous Poisson processes (NHPP) observed with noise, focusing on previously unstudied second-order characteristics of the noisy process. Utilizing a hierarchical Bayesian model with noisy data, we estimate hyperparameters governing a physically motivated NHPP intensity. Simulation studies demonstrate the reliability of this methodology in accurately estimating hyperparameters. Leveraging the posterior distribution, we then infer the probability of detecting a certain number of events within a given radius, the k-contact distance. We demonstrate our methodology with an application to observations of fast radio bursts (FRBs) detected by the Canadian Hydrogen Intensity Mapping Experiment’s FRB Project (CHIME/FRB). This approach allows us to identify repeating FRB sources by bounding or directly simulating the probability of observing k physically independent sources within some radius in the detection domain or the probability of coincidence (PC). The new methodology improves the repeater detection PC in 91% of cases when applied to the largest sample of previously classified observations, with a median improvement factor (existing metric over PC from our methodology) of ∼ 4800.

We present the discovery and subsequent 3.2 yr monitoring campaign of the repeating fast radio burst (FRB) FRB 20220529A with CHIME/FRB. We observe a gradual decline in dispersion measure (DM) of −0.881 ± 0.001 pc cm ⁻³ yr ⁻¹ (−1.235 ± 0.001 pc cm ⁻³ yr ⁻¹ in the rest frame), implying a ≥3.5% ± 0.2% decrease in the total electron column in the source environment, and we see scattering timescale variations over weeks to years. We observe a short-lived excursion in which the DM rises by ∼1 pc cm ⁻³ , immediately preceding an increase in transient Faraday rotation measure (RM) of ∼2000 rad m ⁻² previously reported for this source, before returning to its gradual decline in DM. During this DM/RM excursion, we identify a local line-of-sight magnetic field of 3.4 ± 0.2 mG around FRB 20220529A, corresponding to one of the most strongly magnetized FRB environments. We measure a decrease in the linear polarization fraction of FRB 20220529A bursts with decreasing frequency that we attribute to depolarization from multipath propagation in the source environment. We also place a 5 σ upper limit on the spectral luminosity of an associated persistent radio source of ≤5 × 10 ²⁸ erg s ⁻¹ Hz ⁻¹ at 1.5 GHz. These observations are consistent with FRB 20220529A originating from a young (approximately years to centuries old) expanding supernova remnant, with short-lived DM and RM variability arising from interactions with the supernova remnant or with a binary companion.

We present a catalog of 4539 fast radio bursts (FRBs) observed with the Canadian Hydrogen Intensity Mapping Experiment telescope between 2018 July 25 and 2023 September 15. These bursts originate from 3641 unique sources, including 981 bursts from 83 known repeating sources. For each FRB, the catalog provides an O ( 1 0 ′ ) estimate of sky location along with corresponding measurements of cumulative exposure time and survey sensitivity over the observing period. It includes a total-intensity dynamic spectrum between 400 and 800 MHz at 0.983 ms resolution. From this spectrum, we constrain a model of the burst morphology and measure key parameters such as arrival time, intrinsic temporal width, dispersion measure, scattering time, and flux density. This second catalog includes all FRBs from the first catalog, with every event reprocessed using a uniform and improved analysis framework. We show that previously published inferences remain valid under the updated measurements. We assess consistency of the detection rate across observational parameters, present initial distributions of burst properties, and outline ongoing and future studies that will use this catalog to investigate the nature of FRBs and their utility as astrophysical and cosmological probes.

Among the thousands of observed fast radio bursts (FRBs), a few sources exhibit exceptionally high burst activity observable by many telescopes across a broad range of radio frequencies. Almost all of these highly active repeaters have been discovered by the Canadian Hydrogen Intensity Mapping Experiment/FRB project (CHIME/FRB), due to its daily observations of the entire northern sky as a transit radio telescope. FRB 20240114A is a source discovered and reported by CHIME/FRB to the community in 2024 January; given its low declination, even the detection of a few bursts hints at a high burst rate. Following the community announcement of this source as a potentially active repeater, it was extensively followed up by other observatories and has emerged as one of the most prolific FRB repeaters ever observed. This paper presents the five bursts CHIME/FRB observed from FRB 20240114A, with channelized raw voltage data saved for two bursts. We do not observe changes in the dispersion measure of the source greater than ∼1.3 pc cm ⁻³ in our observations over a nearly 1 yr baseline. We find a rotation measure of ∼+320 rad m ⁻² . We do not find evidence for scattering at the level of <0.3 ms in the bursts, and we find no evidence for astrophysical scintillation. In our observations of FRB 20240114A, we see a burst rate ∼49 times higher than the median upper limit on the burst rate of apparent nonrepeaters also discovered by CHIME/FRB. With many thousands of bursts observed to date, FRB 20240114A has given the field an extraordinary opportunity to extensively study an FRB and understand its origins.

We analyze the positional and morphological properties of about 3600 unique fast radio burst (FRB) sources reported in the second FRB catalog generated by the Canadian Hydrogen Intensity Mapping Experiment (CHIME) telescope. We find a two-dimensional dependence of FRB detections on sky position and identify a significant absence of detections in a roughly circular region centered at Galactic coordinates (77 . ° 7, 0 . ° 9), spanning an area of 213.6 deg ² . This detection gap spatially coincides with the Cygnus X region—a plasma-rich star-forming region in the Milky Way. This feature is most likely the result of increased sky temperature and strong multipath scattering by turbulent ionized plasma, which broadens the FRB signals beyond detectability in the CHIME band. Our simulations yield a mean of six expected FRB detections within the gap when accounting for the elevated sky temperature in the direction of the detection gap. We infer that a lower limit of the maximum scattering timescale τ _{sc, 1 GHz} ≥ 5.59 ms, obtained without assuming a model of the Galactic electron distribution, is sufficient to suppress the brightness of all coincident FRBs. A similar suppression is seen in Catalog 2 along other high emission measure (EM) sight lines (i.e., EM ≥ 2900 pc cm ⁻⁶ ), further supporting a broader trend of suppression due to Galactic scattering. Future very long baseline interferometry measurements of scattering disks with CHIME Outriggers can help confirm our interpretation. Our work highlights the notion that FRBs can serve as new, model-independent tracers of the warm ionized medium within our Galaxy.