8 research outputs found
An Injection System for the CHIME/FRB Experiment
Dedicated surveys searching for Fast Radio Bursts (FRBs) are subject to
selection effects which bias the observed population of events. Software
injection systems are one method of correcting for these biases by injecting a
mock population of synthetic FRBs directly into the realtime search pipeline.
The injected population may then be used to map intrinsic burst properties onto
an expected signal-to-noise ratio (SNR), so long as telescope characteristics
such as the beam model and calibration factors are properly accounted for. This
paper presents an injection system developed for the Canadian Hydrogen
Intensity Mapping Experiment Fast Radio Burst project (CHIME/FRB). The system
was tested to ensure high detection efficiency, and the pulse calibration
method was verified. Using an injection population of ~85,000 synthetic FRBs,
we found that the correlation between fluence and SNR for injected FRBs was
consistent with that of CHIME/FRB detections in the first CHIME/FRB catalog. We
also noted that the sensitivity of the telescope varied strongly as a function
of the broadened burst width, but not as a function of the dispersion measure.
We conclude that some of the machine-learning based Radio Frequency
Interference (RFI) mitigation methods used by CHIME/FRB can be re-trained using
injection data to increase sensitivity to wide events, and that planned
upgrades to the presented injection system will allow for determining a more
accurate CHIME/FRB selection function in the near future.Comment: 13 pages, 8 figures. Submitted to A
Sub-second periodicity in a fast radio burst
Fast radio bursts (FRBs) are millisecond-duration flashes of radio waves that
are visible at distances of billions of light-years. The nature of their
progenitors and their emission mechanism remain open astrophysical questions.
Here we report the detection of the multi-component FRB 20191221A and the
identification of a periodic separation of 216.8(1) ms between its components
with a significance of 6.5 sigmas. The long (~3 s) duration and nine or more
components forming the pulse profile make this source an outlier in the FRB
population. Such short periodicity provides strong evidence for a neutron-star
origin of the event. Moreover, our detection favours emission arising from the
neutron-star magnetosphere, as opposed to emission regions located further away
from the star, as predicted by some models.Comment: Updated to conform to the accepted versio
Inferring the Energy and Distance Distributions of Fast Radio Bursts Using the First CHIME/FRB Catalog
Fast radio bursts (FRBs) are brief, energetic, typically extragalactic flashes of radio emission whose progenitors are largely unknown. Although studying the FRB population is essential for understanding how these astrophysical phenomena occur, such studies have been difficult to conduct without large numbers of FRBs and characterizable observational biases. Using the recently released catalog of 536 FRBs published by the Canadian Hydrogen Intensity Mapping Experiment/Fast Radio Burst (CHIME/FRB) collaboration, we present a study of the FRB population that also calibrates for selection effects. Assuming a Schechter function, we infer a characteristic energy cut-off of erg and a differential power-law index of γ = . Simultaneously, we infer a volumetric rate of [ (stat.) Gpc ^−3 yr ^−1 above a pivot energy of 10 ^39 erg and below a scattering timescale of 10 ms at 600 MHz, and find we cannot significantly constrain the cosmic evolution of the FRB population with star-formation rate. Modeling the host’s dispersion measure (DM) contribution as a log-normal distribution and assuming a total Galactic contribution of 80 pc cm ^−3 , we find a median value of pc cm ^−3 , comparable with values typically used in the literature. Proposed models for FRB progenitors should be consistent with the energetics and abundances of the full FRB population predicted by our results. Finally, we infer the redshift distribution of FRBs detected with CHIME, which will be tested with the localizations and redshifts enabled by the upcoming CHIME/FRB Outriggers project
The First CHIME/FRB Fast Radio Burst Catalog
We present a catalog of 535 fast radio bursts (FRBs) detected by the Canadian
Hydrogen Intensity Mapping Experiment Fast Radio Burst (CHIME/FRB) Project
between 400 and 800 MHz from 2018 July 25 to 2019 July 1, including 61 bursts
from 18 previously reported repeating sources. The catalog represents the first
large sample, including bursts from repeaters and non-repeaters, observed in a
single survey with uniform selection effects. This facilitates comparative and
absolute studies of the FRB population. We show that repeaters and apparent
non-repeaters have sky locations and dispersion measures (DMs) that are
consistent with being drawn from the same distribution. However, bursts from
repeating sources differ from apparent non-repeaters in intrinsic temporal
width and spectral bandwidth. Through injection of simulated events into our
detection pipeline, we perform an absolute calibration of selection effects to
account for systematic biases. We find evidence for a population of FRBs -
comprising a large fraction of the overall population - with a scattering time
at 600 MHz in excess of 10 ms, of which only a small fraction are observed by
CHIME/FRB. We infer a power-law index for the cumulative fluence distribution
of ,
consistent with the expectation for a non-evolving population in
Euclidean space. We find is steeper for high-DM events and shallower
for low-DM events, which is what would be expected when DM is correlated with
distance. We infer a sky rate of
above a fluence of 5 Jy ms at 600 MHz, with scattering time at MHz under
10 ms, and DM above 100 pc cm.Comment: 66 pages, 27 figures, 5 tables. Submitted to ApJ