scholarly journals Piggyback search for fast radio bursts using Nanshan 26 m and Kunming 40 m radio telescopes – I. Observing and data analysis systems, discovery of a mysterious peryton

2019 ◽  
Vol 488 (3) ◽  
pp. 3957-3971 ◽  
Author(s):  
Y P Men ◽  
R Luo ◽  
M Z Chen ◽  
L F Hao ◽  
K J Lee ◽  
...  
Keyword(s):  
Radio Telescope ◽  
Interference Mitigation ◽  
Matched Filter ◽  
Signal To Noise Ratio ◽  
Dispersion Measure ◽  
Radio Bursts ◽  
Similar Frequency ◽  
New Radio ◽  
Radio Signals ◽  
Measure Index

ABSTRACT We present our piggyback search for fast radio bursts using the Nanshan 26 m Radio Telescope and the Kunming 40 m Radio Telescope. The observations are performed in the L band from 1380 to 1700 MHz at Nanshan and the Sband from 2170 to 2310 MHz at Kunming. We built the roach2-based FFT spectrometer and developed the real-time transient search software. We introduce a new radio interference mitigation technique named zero-DM matched filter and give the formula of the signal-to-noise ratio loss in the transient search. Though we have no positive detection of bursts in about 1600 and 2400 h data at Nanshan and Kunming, respectively, an intriguing peryton was detected at Nanshan, from which hundreds of bursts were recorded. Perytons are terrestrial radio signals that mimic celestial fast radio bursts. They were first reported at Parkes and identified as microwave oven interferences later. The bursts detected at Nanshan show similar frequency swept emission and have double-peaked profiles. They appeared in different sky regions in about tens of minutes observations and the dispersion measure index is not exactly 2, which indicates the terrestrial origin. The peryton differs drastically from the known perytons detected at Parkes, because it appeared in a precise period of p = 1.712 87 ± 0.000 04 s. Its origin remains unknown.

scholarly journals The Northern Cross fast radio burst project – I. Overview and pilot observations at 408 MHz

2020 ◽  
Vol 494 (1) ◽  
pp. 1229-1236 ◽  
Author(s):  
Nicola T Locatelli ◽  
Gianni Bernardi ◽  
Germano Bianchi ◽  
Riccardo Chiello ◽  
Alessio Magro ◽  
...  
Keyword(s):  
Radio Burst ◽  
System Performance ◽  
Field Of View ◽  
High Dispersion ◽  
Dispersion Measure ◽  
Radio Bursts ◽  
Radio Telescopes ◽  
Present Test ◽  
New Radio ◽  
Fast Radio Burst

ABSTRACT Fast radio bursts (FRBs) remain one of the most enigmatic astrophysical sources. Observations have significantly progressed over the last few years, due to the capabilities of new radio telescopes and the refurbishment of existing ones. Here, we describe the upgrade of the Northern Cross radio telescope, operating in the 400–416 MHz frequency band, with the ultimate goal of turning the array into a dedicated instrument to survey the sky for FRBs. We present test observations of the pulsar B0329+54 to characterize the system performance and forecast detectability. Observations with the system currently in place are still limited by modest sky coverage (∼9.4 deg2) and biased by smearing of high dispersion measure events within each frequency channels. In its final, upgraded configuration, however, the telescope will be able to carry out unbiased FRB surveys over a ∼350 deg2 instantaneous field of view up to z ∼ 5, with a (nearly constant) $\sim 760 \, (\tau /{\rm ms})^{-0.5}$ mJy rms sensitivity.

scholarly journals Low Frequency Radio Emission of Pulsar PSR J1907+0919 Associated with the Magnetar SGR1900+14

2000 ◽  
Vol 177 ◽  
pp. 685-689 ◽  
Author(s):  
Yu. P. Shitov ◽  
V. D. Pugachev ◽  
S. M. Kutuzov
Keyword(s):  
Magnetic Field ◽  
Radio Emission ◽  
Radio Telescope ◽  
Timing Analysis ◽  
Low Frequency ◽  
Dispersion Measure ◽  
Superstrong Magnetic Field ◽  
New Radio ◽  
S Period ◽  
Soft Gamma Repeater

AbstractThe soft gamma repeater SGR 1900+14 was observed in Pushchino observatory since 1988 December using BSA radio telescope operating at 111 MHz. We have detected the pulsed radio emission (Shitov 1999) with the same 5.16 s period that was reported earlier for this object (Hurley et al. 1998). The timing analysis has shown that this new radio pulsar PSR J1907+0919 associated with SGR 1900+14 has a superstrong magnetic field, which is 8.1 · 1014G, thereby confirming that it is a ”magnetar” (Duncan & Thompson 1992; Kouveliotou et al. 1999). The dispersion measure of PSR J1907+0919 is 281.4(9)pc·cm−3which gives an estimate of the pulsar’s distance as about 5.8 kpc.

scholarly journals Commensal discovery of four fast radio bursts during Parkes Pulsar Timing Array observations

2019 ◽  
Vol 488 (1) ◽  
pp. 868-875 ◽  
Author(s):  
S Osłowski ◽  
R M Shannon ◽  
V Ravi ◽  
J F Kaczmarek ◽  
S Zhang ◽  
...  
Keyword(s):  
Radio Telescope ◽  
Spectral Properties ◽  
Signal To Noise Ratio ◽  
Radio Bursts ◽  
Signal To Noise ◽  
Fundamental Physics ◽  
Millisecond Pulsars ◽  
Pulsar Timing ◽  
Physics Experiments ◽  
Pulsar Timing Array

ABSTRACT The Parkes Pulsar Timing Array (PPTA) project monitors two dozen millisecond pulsars (MSPs) in order to undertake a variety of fundamental physics experiments using the Parkes 64-m radio telescope. Since 2017 June, we have been undertaking commensal searches for fast radio bursts (FRBs) during the MSP observations. Here, we report the discovery of four FRBs (171209, 180309, 180311, and 180714). The detected events include an FRB with the highest signal-to-noise ratio ever detected at the Parkes Observatory, which exhibits unusual spectral properties. All four FRBs are highly polarized. We discuss the future of commensal searches for FRBs at Parkes.

scholarly journals Modified Radar Signal Model using NLFM

2019 ◽  
Vol 8 (2S3) ◽  
pp. 513-516
Keyword(s):  
Interference Mitigation ◽  
Matched Filter ◽  
Signal To Noise Ratio ◽  
Nonlinear Function ◽  
Side Lobe ◽  
Radar Signal ◽  
Target Range ◽  
Nonlinear Frequency ◽  
Good Resolution ◽  
Signal Model

Intended to the setback of high side lobes of the linear frequency modulation (LFM) signal, we put forward a new signal model using nonlinear frequency (NLFM) signal to overcome the issue. NLFM is a promising way for achieving lower signal to noise ratio, good resolution and better interference mitigation. The novel signal model is designed to enhance the target range estimation and to reduce the side lobe levels. In this paper, a new signal model is designed based on the principle of fusion of two stages. First stage is exponential based nonlinear function and the second stage is a linear function. The simulations were performed for the designed signal model and are compared with the NLFM signal designed using two stage LFM functions. Simulation results show that the designed signal has significant reduction in side lobe levels of the matched filter response

scholarly journals A dispersion excess from pulsar wind nebulae and supernova remnants: Implications for pulsars and FRBs

2020 ◽  
Vol 634 ◽  
pp. A105 ◽  
Author(s):  
S. M. Straal ◽  
L. Connor ◽  
J. van Leeuwen
Keyword(s):  
Magnetic Field ◽  
High Magnetic Field ◽  
Supernova Remnants ◽  
Control Sample ◽  
Dispersion Measure ◽  
Radio Bursts ◽  
Pulsar Wind Nebulae ◽  
Electron Densities ◽  
Radio Signals ◽  
Pulsar Wind

Young pulsars and the pulsar wind nebulae (PWNe) or supernova remnants (SNRs) that surround them are some of the most dynamic and high-powered environments in our Universe. With the rise of more sensitive observations, the number of pulsar-SNR and PWN associations (hereafter, SNR/PWN) has increased, yet we do not understand to which extent this environment influences the pulsars’ impulsive radio signals. We studied the dispersive contribution of SNRs and PWNe on Galactic pulsars, and considered their relevance to fast radio bursts (FRBs) such as FRB 121102. We investigated the dispersion measure (DM) contribution of SNRs and PWNe by comparing the measured DMs of Galactic pulsars in a SNR/PWN to the DM expected only from the intervening interstellar electrons, using the NE2001 model. We find that a two-σ DM contribution of SNRs and PWNe to the pulsar signal exists, amounting to 21.1 ± 10.6 pc cm−3. The control sample of pulsars unassociated with a SNR/PWN shows no excess. We model the SNR and PWN electron densities for each young pulsar in our sample and show that these indeed predict an excess of this magnitude. By extrapolating to the kind of fast-spinning, high magnetic field, young pulsars that may power FRBs, we show their SNR and PWN are capable of significantly contributing to the observed DM.

New Radio-telescope

Nature ◽  
1967 ◽  
Vol 213 (5075) ◽  
pp. 432-433
Keyword(s):  
Radio Telescope ◽  
New Radio

scholarly journals Pulsar science with the CHIME telescope

2017 ◽  
Vol 13 (S337) ◽  
pp. 179-182 ◽  
Author(s):  
Cherry Ng
Keyword(s):  
Northern Hemisphere ◽  
Radio Telescope ◽  
Field Of View ◽  
Radio Bursts ◽  
Radio Telescopes ◽  
Acoustic Oscillations ◽  
Daily Monitoring ◽  
Intensity Mapping ◽  
Pulsar Timing ◽  
Pulsar Timing Array

AbstractThe CHIME telescope (the Canadian Hydrogen Intensity Mapping Experiment) recently built in Penticton, Canada, is currently being commissioned. Originally designed as a cosmology experiment, it was soon recognized that CHIME has the potential to simultaneously serve as an incredibly useful radio telescope for pulsar science. CHIME operates across a wide bandwidth of 400–800 MHz and will have a collecting area and sensitivity comparable to that of the 100-m class radio telescopes. CHIME has a huge field of view of ~250 square degrees. It will be capable of observing 10 pulsars simultaneously, 24-hours per day, every day, while still accomplishing its missions to study Baryon Acoustic Oscillations and Fast Radio Bursts. It will carry out daily monitoring of roughly half of all pulsars in the northern hemisphere, including all NANOGrav pulsars employed in the Pulsar Timing Array project. It will cycle through all pulsars in the northern hemisphere with a range of cadence of no more than 10 days.

scholarly journals Yebes 40 m radio telescope and the broad band Nanocosmos receivers at 7 mm and 3 mm for line surveys

2021 ◽  
Vol 645 ◽  
pp. A37
Author(s):  
F. Tercero ◽  
J. A. López-Pérez ◽  
J. D. Gallego ◽  
F. Beltrán ◽  
O. García ◽  
...  
Keyword(s):  
Radio Telescope ◽  
Signal To Noise Ratio ◽  
Broad Band ◽  
High Sensitivity ◽  
Lower Sensitivity ◽  
Molecular Chemistry ◽  
Long Baseline ◽  
New Instrumentation ◽  
Frequency Coverage ◽  
Technical Specifications

Context. Yebes 40 m radio telescope is the main and largest observing instrument at Yebes Observatory and is devoted to very long baseline interferometry (VLBI) and single-dish observations since 2010. It has been covering frequency bands between 2 GHz and 90 GHz in discontinuous and narrow windows in most cases in order to match the current needs of the European VLBI Network (EVN) and the Global Millimeter VLBI Array (GMVA). Aims. The Nanocosmos project, a European Union-funded synergy grant, has enabled an increase in the instantaneous frequency coverage of the Yebes 40 m radio telescope, making it possible to observe many molecular transitions with single tunings in single-dish mode. This reduces the observing time and maximises the output from the telescope. Methods. We present technical specifications of the recently installed 31.5−50 GHz (Q band) and 72−90.5 GHz (W band) receivers along with the main characteristics of the telescope at these frequency ranges. We observed IRC+10216, CRL 2688, and CRL 618, which harbour a rich molecular chemistry, to demonstrate the capabilities of the new instrumentation for spectral observations in single-dish mode. Results. Our results show the high sensitivity of the telescope in the Q band. The spectrum of IRC+10126 offers an unprecedented signal-to-noise ratio for this source in this band. On the other hand, the spectrum normalised by the continuum flux towards CRL 618 in the W band demonstrates that the 40 m radio telescope produces comparable results to those from the IRAM 30 m radio telescope, although with a lower sensitivity. The new receivers fulfil one of the main goals of Nanocosmos and open up the possibility to study the spectrum of different astrophysical media with unprecedented sensitivity.

scholarly journals Code Optimisation Framework for Multicode Sonar Systems

2021 ◽  
Author(s):  
◽  
Muhammad Rashed
Keyword(s):  
Transmission Loss ◽  
Matched Filter ◽  
Signal To Noise Ratio ◽  
Welch Bound ◽  
Optimisation Algorithm ◽  
Sonar System ◽  
Channel Effects ◽  
Sonar Systems ◽  
Mismatched Filters ◽  
Quadratically Constrained

<p>The ocean is a temporally and spatially varying environment, the characteristics of which pose significant challenges to the development of effective underwater wireless communications and sensing systems.  An underwater sensing system such as a sonar detects the presence of a known signal through correlation. It is advantageous to use multiple transducers to increase surveying area with reduced surveying costs and time. Each transducers is assigned a dedicated code. When using multiple codes, the sidelobes of auto- and crosscorrelations are restricted to theoretical limits known as bounds. Sets of codes must be optimised in order to achieve optimal correlation properties, and, achieve Sidelobe Level (SLL)s as low as possible.  In this thesis, we present a novel code-optimisation method to optimise code-sets with any number of codes and up to any length of each code. We optimise code-sets for a matched filter for application in a multi-code sonar system. We first present our gradient-descent based algorithm to optimise sets of codes for flat and low crosscorrelations and autocorrelation sidelobes, including conformance of the magnitude of the samples of the codes to a target power profile. We incorporate the transducer frequency response and the channel effects into the optimisation algorithm. We compare the correlations of our optimised codes with the well-known Welch bound. We then present a method to widen the autocorrelation mainlobe and impose monotonicity. In many cases, we are able to achieve SLLs beyond the Welch bound.  We study the Signal to Noise Ratio (SNR) improvement of the optimised codes for an Underwater Acoustic (UWA) channel. During its propagation, the acoustic wave suffers non-constant transmission loss which is compensated by the application of an appropriate Time Variable Gain (TVG). The effect of the TVG modifies the noise received with the signal. We show that in most cases, the matched filter is still the optimum filter. We also show that the accuracy in timing is very important in the application of the TVG to the received signal.  We then incorporate Doppler tolerance into the existing optimisation algorithm. Our proposed method is able to optimise sets of codes for multiple Doppler scaling factors and non-integer delays in the arrival of the reflection, while still conforming to other constraints.  We suggest designing mismatched filters to further reduce the SLLs, firstly using an existing Quadratically Constrained Qaudratic Program (QCQP) formulation and secondly, as a local optimisation problem, modifying our basic optimisation algorithm.</p>

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