4 research outputs found
CHIME/FRB Discovery of 25 Repeating Fast Radio Burst Sources
We present the discovery of 25 new repeating fast radio burst (FRB) sources
found among CHIME/FRB events detected between 2019 September 30 and 2021 May 1.
The sources were found using a new clustering algorithm that looks for multiple
events co-located on the sky having similar dispersion measures (DMs). The new
repeaters have DMs ranging from 220 pc cm to 1700 pc
cm, and include sources having exhibited as few as two bursts to as many
as twelve. We report a statistically significant difference in both the DM and
extragalactic DM (eDM) distributions between repeating and apparently
nonrepeating sources, with repeaters having lower mean DM and eDM, and we
discuss the implications. We find no clear bimodality between the repetition
rates of repeaters and upper limits on repetition from apparently nonrepeating
sources after correcting for sensitivity and exposure effects, although some
active repeating sources stand out as anomalous. We measure the repeater
fraction and find that it tends to an equilibrium of % over
our exposure thus far. We also report on 14 more sources which are promising
repeating FRB candidates and which merit follow-up observations for
confirmation.Comment: Submitted to ApJ. Comments are welcome and follow-up observations are
encouraged
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
Updating the First CHIME/FRB Catalog of Fast Radio Bursts with Baseband Data
International audienceIn 2021, a catalog of 536 fast radio bursts (FRBs) detected with the Canadian Hydrogen Intensity Mapping Experiment (CHIME) radio telescope was released by the CHIME/FRB Collaboration. This large collection of bursts, observed with a single instrument and uniform selection effects, has advanced our understanding of the FRB population. Here we update the results for 140 of these FRBs for which channelized raw voltage ("baseband") data are available. With the voltages measured by the telescope's antennas, it is possible to maximize the telescope sensitivity in any direction within the primary beam, an operation called "beamforming." This allows us to increase the signal-to-noise ratios of the bursts and to localize them to subarcminute precision. The improved localizations are also used to correct the beam response of the instrument and to measure fluxes and fluences with an ∼10% uncertainty. Additionally, the time resolution is increased by 3 orders of magnitude relative to that in the first CHIME/FRB catalog, and, applying coherent dedispersion, burst morphologies can be studied in detail. Polarization information is also available for the full sample of 140 FRBs, providing an unprecedented data set to study the polarization properties of the population. We release the baseband data beamformed to the most probable position of each FRB. These data are analyzed in detail in a series of accompanying papers
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