The discovery of a repeating fast radio burst (FRB) source
, FRB 121102, eliminated models involving cataclysmic events for this source. No other repeating FRB has hitherto been detected despite many ...recent discoveries and follow-ups
, suggesting that repeaters may be rare in the FRB population. Here we report the detection of six repeat bursts from FRB 180814.J0422+73, one of the 13 FRBs detected
by the Canadian Hydrogen Intensity Mapping Experiment (CHIME) FRB project
during its pre-commissioning phase in July and August 2018. These repeat bursts are consistent with originating from a single position on the sky, with the same dispersion measure, about 189 pc cm
. This traces approximately twice the expected Milky Way column density, and implies an upper limit on the source redshift of 0.1, at least a factor of about 2 closer than FRB 121102
. In some of the repeat bursts, we observe sub-pulse frequency structure, drifting, and spectral variation reminiscent of that seen in FRB 121102
, suggesting similar emission mechanisms and/or propagation effects. This second repeater, found among the first few CHIME/FRB discoveries, suggests that there exists-and that CHIME/FRB and other wide-field, sensitive radio telescopes will find-a substantial population of repeating FRBs.
Fast radio bursts (FRBs) are highly dispersed millisecond-duration radio flashes probably arriving from far outside the Milky Way
. This phenomenon was discovered at radio frequencies near 1.4 GHz ...and so far has been observed in one case
at as high as 8 GHz, but not below 700 MHz in spite of significant searches at low frequencies
. Here we report detections of 13 FRBs at radio frequencies as low as 400 MHz, on the Canadian Hydrogen Intensity Mapping Experiment (CHIME) using the CHIME/FRB instrument
. They were detected during a telescope pre-commissioning phase, when our sensitivity and field-of-view were not yet at design specifications. Emission in multiple events is seen down to 400 MHz, the lowest radio frequency to which we are sensitive. The FRBs show various temporal scattering behaviours, with the majority significantly scattered, and some apparently unscattered to within measurement uncertainty even at our lowest frequencies. Of the 13 reported here, one event has the lowest dispersion measure yet reported, implying that it is among the closest yet known, and another has shown multiple repeat bursts, as described in a companion paper
. The overall scattering properties of our sample suggest that FRBs as a class are preferentially located in environments that scatter radio waves more strongly than the diffuse interstellar medium in the Milky Way.
We present results from a new incoherent-beam fast radio burst (FRB) search on the Canadian Hydrogen Intensity Mapping Experiment (CHIME) Pathfinder. Its large instantaneous field of view (FoV) and ...relative thermal insensitivity allow us to probe the ultra-bright tail of the FRB distribution, and to test a recent claim that this distribution's slope, , is quite small. A 256-input incoherent beamformer was deployed on the CHIME Pathfinder for this purpose. If the FRB distribution were described by a single power law with = 0.7, we would expect an FRB detection every few days, making this the fastest survey on the sky at present. We collected 1268 hr of data, amounting to one of the largest exposures of any FRB survey, with over 2.4 × 105 deg2 hr. Having seen no bursts, we have constrained the rate of extremely bright events to <13 sky−1 day−1 above for τ between 1.3 and 100 ms, at 400-800 MHz. The non-detection also allows us to rule out 0.9 with 95% confidence, after marginalizing over uncertainties in the GBT rate at 700-900 MHz, though we show that for a cosmological population and a large dynamic range in flux density, is brightness dependent. Since FRBs now extend to large enough distances that non-Euclidean effects are significant, there is still expected to be a dearth of faint events and relative excess of bright events. Nevertheless we have constrained the allowed number of ultra-intense FRBs. While this does not have significant implications for deeper, large-FoV surveys like full CHIME and APERTIF, it does have important consequences for other wide-field, small dish experiments.
The CHIME Pulsar Project: System Overview Amiri, M.; Bandura, K. M.; Boyle, P. J. ...
The Astrophysical journal. Supplement series,
07/2021, Letnik:
255, Številka:
1
Journal Article
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Abstract
We present the design, implementation, and performance of the digital pulsar observing system constructed for the Canadian Hydrogen Intensity Mapping Experiment (CHIME). Using accelerated ...computing, this system processes independent, digitally steered beams formed by the CHIME correlator to simultaneously observe up to 10 radio pulsars and transient sources. Each of these independent streams is processed by the CHIME/Pulsar back-end system, which can coherently dedisperse, in real time, up to dispersion measure values of 2500 pc cm
−3
. The tracking beams and real-time analysis system are autonomously controlled by a priority-based algorithm that schedules both known sources and positions of interest for observation with observing cadences as rapid as 1 day. Given the distribution of known pulsars and radio-transient sources and the dynamic scheduling, the CHIME/Pulsar system can monitor 400–500 positions once per sidereal day and observe most sources with declinations greater than −20° once every ∼4 weeks. We also discuss the extensive science program enabled through the current modes of data acquisition for CHIME/Pulsar that centers on timing and searching experiments.
Magnetars are highly magnetized young neutron stars that occasionally produce enormous bursts and flares of X-rays and γ-rays
. Of the approximately thirty magnetars currently known in our Galaxy and ...the Magellanic Clouds, five have exhibited transient radio pulsations
. Fast radio bursts (FRBs) are millisecond-duration bursts of radio waves arriving from cosmological distances
, some of which have been seen to repeat
. A leading model for repeating FRBs is that they are extragalactic magnetars, powered by their intense magnetic fields
. However, a challenge to this model is that FRBs must have radio luminosities many orders of magnitude larger than those seen from known Galactic magnetars. Here we report the detection of an extremely intense radio burst from the Galactic magnetar SGR 1935+2154 using the Canadian Hydrogen Intensity Mapping Experiment (CHIME) FRB project. The fluence of this two-component bright radio burst and the estimated distance to SGR 1935+2154 together imply a burst energy at 400 to 800 megahertz of approximately 3 × 10
erg, which is three orders of magnitude higher than the burst energy of any radio-emitting magnetar detected thus far. Such a burst coming from a nearby galaxy (at a distance of less than approximately 12 megaparsecs) would be indistinguishable from a typical FRB. However, given the large gaps in observed energies and activity between the brightest and most active FRB sources and what is observed for SGR 1935+2154-like magnetars, more energetic and active sources-perhaps younger magnetars-are needed to explain all observations.
Fast radio bursts (FRBs) are bright, millisecond-duration radio transients originating from sources at extragalactic distances
, the origin of which is unknown. Some FRB sources emit repeat bursts, ...ruling out cataclysmic origins for those events
. Despite searches for periodicity in repeat burst arrival times on timescales from milliseconds to many days
, these bursts have hitherto been observed to appear sporadically and-although clustered
-without a regular pattern. Here we report observations of a 16.35 ± 0.15 day periodicity (or possibly a higher-frequency alias of that periodicity) from the repeating FRB 180916.J0158+65 detected by the Canadian Hydrogen Intensity Mapping Experiment Fast Radio Burst Project
. In 38 bursts recorded from 16 September 2018 to 4 February 2020 UTC, we find that all bursts arrive in a five-day phase window, and 50 per cent of the bursts arrive in a 0.6-day phase window. Our results suggest a mechanism for periodic modulation either of the burst emission itself or through external amplification or absorption, and disfavour models invoking purely sporadic processes.
We report on the discovery of eight repeating fast radio burst (FRB) sources found using the Canadian Hydrogen Intensity Mapping Experiment (CHIME) telescope. These sources span a dispersion measure ...(DM) range of 103.5-1281 pc cm−3. They display varying degrees of activity: six sources were detected twice, another three times, and one 10 times. These eight repeating FRBs likely represent the bright and/or high-rate end of a distribution of infrequently repeating sources. For all sources, we determine sky coordinates with uncertainties of ∼10′. FRB 180916.J0158+65 has a burst-averaged DM = 349.2 0.3 pc cm−3 and a low DM excess over the modeled Galactic maximum (as low as ∼20 pc cm−3); this source also has a Faraday rotation measure (RM) of −114.6 0.6 rad m−2, which is much lower than the RM measured for FRB 121102. FRB 181030.J1054+73 has the lowest DM for a repeater, 103.5 0.3 pc cm−3, with a DM excess of ∼70 pc cm−3. Both sources are interesting targets for multi-wavelength follow-up due to their apparent proximity. The DM distribution of our repeater sample is statistically indistinguishable from that of the first 12 CHIME/FRB sources that have not yet repeated. We find, with 4 significance, that repeater bursts are generally wider than those of CHIME/FRB bursts that have not repeated, suggesting different emission mechanisms. Many of our repeater events show complex morphologies that are reminiscent of the first two discovered repeating FRBs. The repetitive behavior of these sources will enable interferometric localizations and subsequent host galaxy identifications.
The Canadian Hydrogen Intensity Mapping Experiment (CHIME) is a novel transit radio telescope operating across the 400-800 MHz band. CHIME is composed of four 20 m × 100 m semicylindrical paraboloid ...reflectors, each of which has 256 dual-polarization feeds suspended along its axis, giving it a 200 deg2 field of view. This, combined with wide bandwidth, high sensitivity, and a powerful correlator, makes CHIME an excellent instrument for the detection of fast radio bursts (FRBs). The CHIME Fast Radio Burst Project (CHIME/FRB) will search beam-formed, high time and frequency resolution data in real time for FRBs in the CHIME field of view. Here we describe the CHIME/FRB back end, including the real-time FRB search and detection software pipeline, as well as the planned offline analyses. We estimate a CHIME/FRB detection rate of 2-42 FRBs sky-1 day-1 normalizing to the rate estimated at 1.4 GHz by Vander Wiel et al. Likely science outcomes of CHIME/FRB are also discussed. CHIME/FRB is currently operational in a commissioning phase, with science operations expected to commence in the latter half of 2018.
We present the design, implementation and performance of a digital backend constructed for the Canadian Hydrogen Intensity Mapping Experiment (CHIME) that uses accelerated computing to observe radio ...pulsars and transient radio sources. When operating, the CHIME correlator outputs 10 independent streams of beamformed data for the CHIME/Pulsar backend that digitally track specified celestial positions. Each of these independent streams are processed by the CHIME/Pulsar backend system which can coherently dedisperse, in real-time, up to dispersion measure values of 2500 pc/cm\(^{-3}\) . The tracking beams and real-time analysis system are autonomously controlled by a priority-based algorithm that schedules both known sources and positions of interest for observation with observing cadences as small as one day. Given the distribution of known pulsars and radio-transient sources, the CHIME/Pulsar system can monitor up to 900 positions once per sidereal day and observe all sources with declinations greater than \(-20^\circ\) once every \(\sim\)2 weeks. We also discuss the science program enabled through the current modes of data acquisition for CHIME/Pulsar that centers on timing and searching experiments.
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