scholarly journals The FRATS project: real-time searches for fast radio bursts and other fast transients with LOFAR at 135 MHz

2019 ◽  
Vol 621 ◽  
pp. A57 ◽  
Author(s):  
S. ter Veen ◽  
J. E. Enriquez ◽  
H. Falcke ◽  
J. P. Rachen ◽  
M. van den Akker ◽  
...  
Keyword(s):  
Real Time ◽  
Low Frequency ◽  
Radio Bursts ◽  
Pilot Survey ◽  
Upper Limit ◽  
Previous Decade ◽  
Fast Transients ◽  
Radio Transients ◽  
The Individual ◽  
Galactic Sources

Context. In the previous decade, two new classes of fast radio transients were detected: the Galactic, rotating radio transients (RRATs) and the extragalactic fast radio bursts (FRBs). If the detectable emission of these objects extends to lower radio frequencies, the LOw Frequency ARray (LOFAR) is ideally suited to seek and localize these transients at frequencies of 10–250 MHz. This is due to LOFAR’s sensitivity, diverse beamform capabilities, and transient buffers for the individual elements that allow post-event imaging of events, potentially at arcsecond resolution. Aims. Our aim is to identify and localize pulses at frequencies below 250 MHz and, in the case of nondetections, derive upper limits on the sky and volume rates of FRBs. Methods. A real-time search program for fast radio transients is installed on the LOFAR systems which runs commensally with other observations, and uses the wide incoherent LOFAR beam (11.25 deg2 at 150 MHz). Buffered data from hundreds of dipoles are used to reconstruct the direction and polarization information of the event, and to distinguish between celestial, terrestrial, and instrumental origins. Results. Observations were taken covering either the frequency range 119–151 MHz or in four frequency bands, each of 2 MHz in width, centered at 124, 149, 156, and 185 MHz. A first pilot survey covered a range of dispersion measures (DM) below 120 pc cm−3, focusing on Galactic sources, and resulted in an upper limit on the transient rate at LOFAR frequencies of less than 1500 events per sky per day above a fluency of 1.6 kJy ms for an 8-ms pulse. A second pilot survey covered a range of DMs below 500 pc cm−3, focusing on extragalactic sources to about 1 Gpc, and resulted in an upper limit of 1400 events per sky per day above a fluency of 6.0 kJy ms for an 8-ms pulse. Using a model for the distance-DM relationship, this equates to an upper limit of 134 events per Gpc3 per day.

scholarly journals Charting the Transient Radio Sky on Sub-Second Time-Scales with LOFAR

2011 ◽  
Vol 7 (S285) ◽  
pp. 104-104
Author(s):  
J. W. T. Hessels ◽  
Keyword(s):  
Time Scales ◽  
Low Frequency ◽  
Radio Bursts ◽  
Radio Telescopes ◽  
Dynamic Nature ◽  
Transient Sources ◽  
Fast Transients ◽  
Radio Transients ◽  
The Universe ◽  
Rotating Radio Transients

SummaryThe LOw Frequency ARray (LOFAR) is a radio interferometric telescope that promises to open a largely unexplored window on transient sources in the “radio sky”, from time-scales of nanoseconds to years. An important aspect of this will be the study of radio-emitting neutron stars in their various incarnations: slow pulsars, young pulsars, millisecond pulsars, magnetars, rotating radio transients, intermittent pulsars, et cetera. Pulsars and their brethren are the prototype of the more general “fast transients”: sub-second, dispersed radio bursts which point the way to extreme, and potentially still unknown, phenomena. For instance, prompt radio bursts from supernovæ and other extra-galactic bursts have been hypothesized; these could prove to be powerful cosmological probes.This talk discussed LOFAR's impressive ability to observe pulsars and to enlarge greatly the discovery space for (even rarer) fast transients. It also presented the latest pulsar observations made during LOFAR's commissioning period. These are demonstrating powerful observing techniques that will be crucial for the next generation of radio telescopes as well as the effort to increase our understanding of the dynamic nature of the Universe.An expanded version of the talk can be found at http://adsabs.harvard.edu/abs/2011A

scholarly journals First interferometric detections of Fast Radio Bursts

2017 ◽  
Vol 13 (S337) ◽  
pp. 322-323
Author(s):  
M. Caleb ◽  
C. Flynn ◽  
M. Bailes ◽  
E. D. Barr ◽  
T. Bateman ◽  
...  
Keyword(s):  
Real Time ◽  
Radio Telescope ◽  
Near Field ◽  
Radio Bursts ◽  
Field Region ◽  
Transient Detection ◽  
Local Sources ◽  
Fast Transient ◽  
Radio Transients ◽  
Better Than

AbstractThe class of radio transients called Fast Radio Bursts (FRBs) encompasses enigmatic single pulses, each unique in its own way, hindering a consensus for their origin. The key to demystifying FRBs lies in discovering many of them in order to identity commonalities – and in real time, in order to find potential counterparts at other wavelengths. The recently upgraded UTMOST in Australia, is undergoing a backend transformation to rise as a fast transient detection machine. The first interferometric detections of FRBs with UTMOST, place their origin beyond the near-field region of the telescope thus ruling out local sources of interference as a possible origin. We have localised these bursts to much better than the ones discovered at the Parkes radio telescope and have plans to upgrade UTMOST to be capable of much better localisation still.

scholarly journals Observations of transients and pulsars with LOFAR international stations and the ARTEMIS backend

2012 ◽  
Vol 8 (S291) ◽  
pp. 492-494 ◽  
Author(s):  
Maciej Serylak ◽  
Aris Karastergiou ◽  
Chris Williams ◽  
Wesley Armour ◽  
Michael Giles ◽  
...  
Keyword(s):  
Real Time ◽  
Low Frequency ◽  
Identification System ◽  
Processing Unit ◽  
Transient Event ◽  
New Radio ◽  
Digital Hardware ◽  
Graphical Processing ◽  
Radio Transients ◽  
Millisecond Radio

AbstractThe LOw Frequency ARray – LOFAR – is a new radio interferometer designed with emphasis on flexible digital hardware instead of mechanical solutions. The array elements, so-called stations, are located in the Netherlands and in neighbouring countries. The design of LOFAR allows independent use of its international stations, which, coupled with a dedicated backend, makes them very powerful telescopes in their own right. This backend is called the Advanced Radio Transient Event Monitor and Identification System (ARTEMIS). It is a combined software/hardware solution for both targeted observations and real-time searches for millisecond radio transients which uses Graphical Processing Unit (GPU) technology to remove interstellar dispersion and detect millisecond radio bursts from astronomical sources in real-time.

Fast Radio Transients: From Pulsars to Fast Radio Bursts

2017 ◽  
Vol 14 (S339) ◽  
pp. 27-32
Author(s):  
B. W. Stappers ◽  
M. Caleb ◽  
L. N. Driessen
Keyword(s):  
Real Time ◽  
Time Scales ◽  
Radio Burst ◽  
Host Galaxy ◽  
Radio Bursts ◽  
Recent Developments ◽  
New Instrumentation ◽  
Fast Radio Burst ◽  
Radio Transients ◽  
Archived Data

AbstractThe radio sky is full of transients, their time-scales ranging from nanoseconds to decades. Recent developments in technology sensitivity and computing capabilities have opened up the short end of that range, and are revealing a plethora of new phenomenologies. Studies of radio transients were previously restricted to analyses of archived data, but are now including real-time analyses. We focus here on Fast Radio Bursts, discuss and compare the properties of the population, and describe what is to date the only known repeating Fast Radio Burst and its host galaxy. We also review what will be possible with the new instrumentation coming online.

scholarly journals On the patchiness of the individual pulse spectra at the very low radio frequencies

2017 ◽  
Vol 13 (S337) ◽  
pp. 412-413
Author(s):  
Xiaoxi Song ◽  
Vladislav Kondratiev ◽  
Anna Bilous
Keyword(s):  
Pulse Sequences ◽  
Low Frequency ◽  
Single Pulse ◽  
Radio Bursts ◽  
Individual Pulse ◽  
Recorded Signal ◽  
Highly Dispersed ◽  
Radio Frequencies ◽  
The Individual

AbstractWe have used sensitive LOw Frequency ARray (LOFAR) observations of PSR B0809+74 at 15–62 MHz to study the anomalously intensive pulses, first reported by Ulyanov et al. (2006) at 18–30 MHz. Similarly to Ulyanov et al., we found that the spectra of strong pulses consist of distinct bright patches. Moreover, these spectral patches were spotted to drift upwards in frequency over the course of several pulse sequences. We established that this drift is not pulsar-intrinsic, but is caused by the broadband ~20 second-long enhancements of recorded signal, which influenced the dispersed tracks of several pulses at once. We speculate on the cause of such enhancements (i.e. propagation or telescope-related) and the ramifications they bring to the single-pulse studies at the very low radio frequencies. Depending on the origin, the phenomenon may also affect the analysis of highly dispersed single pulses at higher radio frequencies, e.g. Fast Radio Bursts.

scholarly journals LOFT-e: Localisation Of Fast Transients with e-MERLIN

2017 ◽  
Vol 13 (S337) ◽  
pp. 422-423
Author(s):  
C. R. H. Walker ◽  
R. P. Breton ◽  
P. A. Harrison ◽  
A. Holloway ◽  
M. J. Keith ◽  
...  
Keyword(s):  
Full Advantage ◽  
Real Time ◽  
Time Resolution ◽  
Observation Time ◽  
Field Of View ◽  
High Time ◽  
High Time Resolution ◽  
Radio Bursts ◽  
Raw Data ◽  
Fast Transients

AbstractThe majority of fast radio bursts (FRBs) are poorly localised, hindering their potential scientific yield as galactic, intergalactic, and cosmological probes. LOFT-e, a digital backend for the U.K.’s e-MERLIN seven-telescope interferometer will provide commensal search and real-time detection of FRBs, taking full advantage of its field of view (FoV), sensitivity, and observation time. Upon burst detection, LOFT-e will store raw data offline, enabling the sub-arcsecond localisation provided by e-MERLIN and expanding the pool of localised FRBs. The high-time resolution backend will additionally introduce pulsar observing capabilities to e-MERLIN.

scholarly journals Limits on absorption from a 332-MHz survey for fast radio bursts

2020 ◽  
Vol 493 (3) ◽  
pp. 4418-4427 ◽  
Author(s):  
K M Rajwade ◽  
M B Mickaliger ◽  
B W Stappers ◽  
C G Bassa ◽  
R P Breton ◽  
...  
Keyword(s):  
Radio Emission ◽  
Compton Scattering ◽  
Low Frequency ◽  
Radio Bursts ◽  
Intensity Mapping ◽  
The Past ◽  
Upper Limit ◽  
Shock Region ◽  
Absorption Models ◽  
Post Shock

ABSTRACT Fast radio bursts (FRBs) are bright, extragalactic radio pulses whose origins are still unknown. Until recently, most FRBs have been detected at frequencies greater than 1 GHz with a few exceptions at 800 MHz. The recent discoveries of FRBs at 400 MHz from the Canadian Hydrogen Intensity Mapping Experiment (CHIME) telescope have opened up possibilities for new insights about the progenitors while many other low-frequency surveys in the past have failed to find any FRBs. Here, we present results from an FRB survey recently conducted at the Jodrell Bank Observatory at 332 MHz with the 76-m Lovell telescope for a total of 58 d. We did not detect any FRBs in the survey and report a 90${{\ \rm per\ cent}}$ upper limit of 5500 FRBs per day per sky for a Euclidean Universe above a fluence threshold of 46 Jy ms. We discuss the possibility of absorption as the main cause of non-detections in low-frequency (<800 MHz) searches and invoke different absorption models to explain the same. We find that Induced Compton Scattering alone cannot account for absorption of radio emission and that our simulations favour a combination of Induced Compton Scattering and Free-Free Absorption to explain the non-detections. For a free–free absorption scenario, our constraints on the electron density are consistent with those expected in the post-shock region of the ionized ejecta in superluminous supernovae.

scholarly journals A Population of Fast Radio Bursts at Cosmological Distances

Science ◽  
2013 ◽  
Vol 341 (6141) ◽  
pp. 53-56 ◽  
Author(s):  
D. Thornton ◽  
B. Stappers ◽  
M. Bailes ◽  
B. Barsdell ◽  
S. Bates ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Galactic Plane ◽  
Host Galaxy ◽  
Source Population ◽  
Radio Bursts ◽  
Host Galaxies ◽  
Fast Transients ◽  
Radio Transients ◽  
The Universe

Searches for transient astrophysical sources often reveal unexpected classes of objects that are useful physical laboratories. In a recent survey for pulsars and fast transients, we have uncovered four millisecond-duration radio transients all more than 40° from the Galactic plane. The bursts’ properties indicate that they are of celestial rather than terrestrial origin. Host galaxy and intergalactic medium models suggest that they have cosmological redshifts of 0.5 to 1 and distances of up to 3 gigaparsecs. No temporally coincident x- or gamma-ray signature was identified in association with the bursts. Characterization of the source population and identification of host galaxies offers an opportunity to determine the baryonic content of the universe.

scholarly journals The AARTFAAC All-Sky Monitor: System Design and Implementation

2016 ◽  
Vol 05 (04) ◽  
pp. 1641008 ◽  
Author(s):  
Peeyush Prasad ◽  
Folkert Huizinga ◽  
Eric Kooistra ◽  
Daniel van der Schuur ◽  
Andre Gunst ◽  
...  
Keyword(s):  
Real Time ◽  
Large Scale ◽  
Low Frequency ◽  
High Sensitivity ◽  
Hierarchical Design ◽  
Minimum Latency ◽  
Analysis Center ◽  
Sky Monitor ◽  
Radio Transients

The Amsterdam–ASTRON Radio Transients Facility and Analysis Center (AARTFAAC) all-sky monitor is a sensitive, real-time transient detector based on the Low Frequency Array (LOFAR). It generates images of the low frequency radio sky with spatial resolution of tens of arcmin, MHz bandwidths, and a time cadence of a few seconds, while simultaneously but independently observing with LOFAR. The image timeseries is then monitored for short and bright radio transients. On detection of a transient, a low latency trigger will be generated for LOFAR, which can interrupt its schedule to carry out follow-up observations of the trigger location at high sensitivity and resolutions. In this paper, we describe our heterogeneous, hierarchical design to manage the 259[Formula: see text]Gbps raw data rate and large scale computing to produce real-time images with minimum latency. We discuss the implementation of the instrumentation, its performance and scalability.

Detection by real-time quaking-induced conversion (RT-QuIC), ELISA, and IHC of chronic wasting disease prion in lymph nodes from Pennsylvania white-tailed deer with specific PRNP genotypes

2021 ◽  
pp. 104063872110214
Author(s):  
Deepanker Tewari ◽  
David Steward ◽  
Melinda Fasnacht ◽  
Julia Livengood
Keyword(s):  
Real Time ◽  
Disease Susceptibility ◽  
Chronic Wasting Disease ◽  
Low Frequency ◽  
The United States ◽  
Detection Methods ◽  
Spongiform Encephalopathy ◽  
Wasting Disease ◽  
Diagnostic Laboratory ◽  
Highly Sensitive

Chronic wasting disease (CWD) is a prion-mediated, transmissible disease of cervids, including deer ( Odocoileus spp.), which is characterized by spongiform encephalopathy and death of the prion-infected animals. Official surveillance in the United States using immunohistochemistry (IHC) and ELISA entails the laborious collection of lymphoid and/or brainstem tissue after death. New, highly sensitive prion detection methods, such as real-time quaking-induced conversion (RT-QuIC), have shown promise in detecting abnormal prions from both antemortem and postmortem specimens. We compared RT-QuIC with ELISA and IHC for CWD detection utilizing deer retropharyngeal lymph node (RLN) tissues in a diagnostic laboratory setting. The RLNs were collected postmortem from hunter-harvested animals. RT-QuIC showed 100% sensitivity and specificity for 50 deer RLN (35 positive by both IHC and ELISA, 15 negative) included in our study. All deer were also genotyped for PRNP polymorphism. Most deer were homozygous at codons 95, 96, 116, and 226 (QQ/GG/AA/QQ genotype, with frequency 0.86), which are the codons implicated in disease susceptibility. Heterozygosity was noticed in Pennsylvania deer, albeit at a very low frequency, for codons 95GS (0.06) and 96QH (0.08), but deer with these genotypes were still found to be CWD prion-infected.

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