Giant Pulses Research Articles

Kinematics of Crab Giant Pulses

Abstract The Crab Pulsar’s radio emission is unusual, consisting predominantly of giant pulses, with durations of about a microsecond but structure down to the nanosecond level, and brightness temperatures of up to 1037 K. It is unclear how giant pulses are produced, but they likely originate near the pulsar’s light cylinder, where corotating plasma approaches the speed of light. We report observations in the 400–800 MHz frequency band, where the pulses are broadened by scattering in the surrounding Crab Nebula. We find that some pulse frequency spectra show strong bands, which vary during the scattering tail, in one case showing a smooth upward drift. While the banding may simply reflect interference between nanosecond scale pulse components, the variation is surprising, as in the scattering tail the only difference is that the source is observed via slightly longer paths, bent by about an arcsecond in the nebula. The corresponding small change in viewing angle could nevertheless reproduce the observed drift by a change in Doppler shift, if the plasma that emitted the giant pulses moved highly relativistically, with a Lorentz factor γ ∼ 104 (and without much spread in γ). If so, this would support models that appeal to highly relativistic plasma to transform ambient magnetic structures to coherent gigahertz radio emission, be it for giant pulses or for potentially related sources, such as fast radio bursts.

An Arecibo Search for Fast Radio Transients from M87

Abstract The possible origin of millisecond bursts from the giant elliptical galaxy M87 has been scrutinized since the earliest searches for extragalactic fast radio transients undertaken in the late 1970s. Motivated by rapid technological advancements in recent years, we conducted ≃10 hr of L-band (1.15–1.75 GHz) observations of the core of M87 with the Arecibo radio telescope in 2019. Adopting a matched filtering approach, we searched our data for single pulses using trial dispersion measures up to 5500 pc cm−3 and burst durations between 0.3–123 ms. We find no evidence of astrophysical bursts in our data above a 7σ detection threshold. Our observations thus constrain the burst rate from M87 to ≲ 0.1 bursts hr−1 above 1.4 Jy ms, the most stringent upper limit obtained to date. Our nondetection of radio bursts is consistent with expectations of giant pulse emission from a Crab-like young neutron star population in M87. However, the dense, strongly magnetized interstellar medium surrounding the central ∼109 M ⊙ supermassive black hole of M87 may potentially harbor magnetars that can emit detectable radio bursts during their flaring states.

Narrow-band giant pulses from the Crab pulsar

ABSTRACT We used a new spectral-fitting technique to identify a subpopulation of 6 narrow-band giant pulses from the Crab pulsar out of a total of 1578. These giant pulses were detected in 77 min of observations with the 46-m dish at the Algonquin Radio Observatory at 400–800 MHz. The narrow-band giant pulses consist of both main- and inter-pulses, thereby being more likely to be caused by an intrinsic emission mechanism as opposed to a propagation effect. Fast radio bursts (FRBs) have demonstrated similar narrow-band features, while only little has been observed in the giant pulses of pulsars. We report the narrow-band giant pulses with Δν/ν of the order of 0.1, which is close to the value of 0.05 reported for the repeater FRB 20190711A. Hence, the connection between FRBs and giant pulses of pulsars is further established.

Spectral filtering effect-induced temporal rogue waves in a Tm-doped fiber laser.

We have experimentally and theoretically investigated optical rogue waves (ORWs) in a net negative dispersion Tm-doped fiber laser with a long cavity, adopting nonlinear polarization evolution as a mode-locker as well as a spectral filter. We obtained a state with numerous pulses bunched in a burst accompanied by perturbation within the burst, in which the spectrum was partially perturbed. After statistical analysis, we found that ORWs have existed in this bunching state. By adjusting the intra-cavity polarization controllers, the perturbed pulse bunching turned into a chaotic pulse bunching state, which gave rise to giant pulses with ultra-high amplitudes, and the giant pulses were a precursor of a broad-spectrum noise-like pulse. The probability of occurrence of ORWs was increased in the chaotic state, which is caused by multi-pulse instability induced by the spectral filtering effect. Simulation results confirm the experimental results and demonstrate that the spectral filter bandwidth (SFB) is directly related to the probability of the emergence of ORWs. When increasing the SFB across the range of multi-pulse instability at a fixed pump power, the frequency with which ORWs appear increases.

A Bright Fast Radio Burst from FRB 20200120E with Sub-100 Nanosecond Structure

Abstract We have detected a bright radio burst from FRB 20200120E with the NASA Deep Space Network (DSN) 70 m dish (DSS-63) at radio frequencies between 2.2 and 2.3 GHz. This repeating fast radio burst (FRB) is reported to be associated with a globular cluster in the M81 galactic system. With high time resolution recording, low scattering, and large intrinsic brightness of the burst, we find a burst duration of ∼30 μs, comprised of several narrow components with typical separations of 2–3 μs. The narrowest component has a width of ≲100 ns, which corresponds to a light travel time size as small as 30 m. The peak flux density of the narrowest burst component is 270 Jy. We estimate the total spectral luminosity of the narrowest component of the burst to be 4 × 1030 erg s−1 Hz−1, which is a factor of ∼500 above the luminosities of the so-called “nanoshots” associated with giant pulses from the Crab pulsar. This spectral luminosity is also higher than that of the radio bursts detected from the Galactic magnetar SGR 1935 + 2154 during its outburst in April 2020, but it falls on the low-end of the currently measured luminosity distribution of extragalatic FRBs, further indicating the presence of a continuum of FRB luminosities. The temporal separation of the individual components has similarities to the quasiperiodic behavior seen in the microstructure of some pulsars. The known empirical relation between the microstructure quasiperiodicity timescale and the rotation period of pulsars possibly suggests a possible pulsar as the source of this FRB, with a rotation period of a few milliseconds.

Macroscopic, layered onion shell like magnetic domain structure generated in YIG films using ultrashort, megagauss magnetic pulses

Study of the formation and evolution of large scale, ordered structures is an enduring theme in science. Generation, evolution and control of large sized magnetic domains are challenging tasks, given the complex nature of competing interactions in a magnetic system. Here, we demonstrate large scale non-coplanar ordering of spins, driven by picosecond, megagauss magnetic pulses derived from a high intensity, femtosecond laser. Our studies on a specially designed yttrium iron garnet (YIG) dielectric/metal film sandwich target, show the creation of complex, large, concentric, elliptical shaped magnetic domains which resemble the layered shell structure of an onion. The largest shell has a major axis over hundreds of micrometers, in stark contrast to sub micrometer scale polygonal, striped or bubble shaped magnetic domains in magnetic materials, or large dumbbell shaped domains produced in magnetic films irradiated with accelerator based relativistic electron beams. Micromagnetic simulations show that the giant magnetic field pulses create ultrafast terahertz (THz) spin waves and a snapshot of these fast-propagating spin waves is stored as the layered onion shell shaped domains in the YIG film. Typically, information transport via spin waves in magnonic devices occurs in the gigahertz regime, where devices are susceptible to thermal disturbances at room temperature. Our intense laser light pulse—YIG sandwich target combination, paves the way for room temperature table-top THz spin wave devices, operating just above or in the range of the thermal noise floor. This dissipation-less device offers ultrafast control of spin information over distances of few hundreds of microns.

Resolving the Emission Regions of the Crab Pulsar’s Giant Pulses

Abstract The Crab pulsar has striking radio emission properties, with the two dominant pulse components—the main pulse and the interpulse—consisting entirely of giant pulses. The emission is scattered in both the Crab Nebula and the interstellar medium, causing multipath propagation and thus scintillation. We study the scintillation of the Crab’s giant pulses using phased Westerbork Synthesis Radio Telescope data at 1668 MHz. We find that giant pulse spectra correlate at only ∼2%, much lower than the one-third correlation expected from a randomized signal imparted with the same impulse response function. In addition, we find that the main pulse and the interpulse appear to scintillate differently; the 2D cross-correlation of scintillation between the interpulse and main pulse has a lower amplitude and is wider in time and frequency delay than the 2D autocorrelation of the main pulses. These lines of evidence suggest that the giant pulse emission regions are extended, and that the main pulse and interpulse arise in physically distinct regions that are resolved by the scattering screen. Assuming the scattering takes place in the nebular filaments, the emission regions are of order a light-cylinder radius, as projected on the sky. With further very long baseline interferometry and multifrequency data, it may be possible to measure the distance to the scattering screens, the size of giant pulse emission regions, and the physical separation between the pulse components.

Galactic Radio Explorer: An All-sky Monitor for Bright Radio Bursts

We present the Galactic Radio Explorer (GReX), an all-sky monitor to probe the brightest bursts in the radio sky. Building on the success of STARE2, we will search for fast radio bursts emitted from Galactic magnetars as well as bursts from nearby galaxies. GReX will search down to ∼ ten microseconds time resolution, allowing us to find new super giant radio pulses from Milky Way pulsars and study their broadband emission. The proposed instrument will employ ultra-wide band (0.7–2 GHz) feeds coupled to a high-performance (receiver temperature <10 K) low noise amplifier originally developed for the DSA-110 and DSA-2000 projects. In GReX Phase I (GReX-I), unit systems will be deployed at Owens Valley Radio Observatory and Big Smoky Valley, Nevada. Phase II will expand the array, placing feeds in India, Australia, and elsewhere in order to build up to continuous coverage of nearly 4π steradians and to increase our exposure to the Galactic plane. We model the local magnetar population to forecast for GReX, finding the improved sensitivity and increased exposure to the Galactic plane could lead to dozens of FRB-like bursts per year.

Performance of a 968-nm laser-diode side-pumped, electro-optical Q-switched Er,Pr:YAP laser with emission at 2.7 μm

We demonstrate the performance of a 968-nm laser-diode (LD) side-pumped Er,Pr:YAP laser in free-running and electro-optical (EO) Q-switched modes with emission at 2.7 μm, respectively. In the free-running mode, a maximum power of 11 W is achieved at a working frequency of 150 Hz and a pulse width of 200 μs, corresponding to the single pulse output energy of 73.3 mJ and slope efficiency of 13.3%. In the EO Q-switching mode, a giant pulse laser is obtained with pulse energy of 20.5 mJ, pulse width of 61.4 ns, and peak power of 0.33 MW at the highest working frequency of 150 Hz, corresponding to the energy extraction efficiency of 71.4%. In addition, dual-wavelength laser at 2713 and 2732 nm and beam quality factors Mx2/My2 of 6.62/6.66 are measured, respectively. The results indicate that a 2.7-μm laser with a high repetition rate and high peak power can be realized through LD side-pumped and EO Q-switched Er,Pr:YAP crystal.

An Arecibo 327 MHz Search for Radio Pulsars and Bursts in the Dwarf Irregular Galaxies Leo A and T

Abstract We have conducted an Arecibo 327 MHz search of two dwarf irregular galaxies in the Local Group, Leo A and T, for radio pulsars and single pulses from fast radio bursts and other giant pulse emitters. We detected no astrophysical signals in this search, and we estimate flux density limits on both periodic and burst emission. Our derived luminosity limits indicate that only the most luminous radio pulsars known in our Galaxy and in the Magellanic Clouds (MCs) would have been detectable in our search if they were at the distances of Leo A and T. Given the much smaller stellar mass content and star formation rates of Leo A and T compared to the Milky Way and the MCs, there are likely to be few (if any) extremely luminous pulsars in these galaxies. It is therefore not surprising that we detected no pulsars in our search.

The Thousand-Pulsar-Array programme on MeerKAT – III. Giant pulse characteristics of PSR J0540−6919

ABSTRACT PSR J0540−6919 is the second-most energetic radio pulsar known and resides in the Large Magellanic Cloud. Like the Crab pulsar, it is observed to emit giant radio pulses (GPs). We used the newly commissioned PTUSE instrument on the MeerKAT radio telescope to search for GPs across three observations. In a total integration time of 5.7 h, we detected 865 pulses above our 7σ threshold. With full polarization information for a subset of the data, we estimated the Faraday rotation measure, $\rm {RM}=-245.8 \pm 1.0$ rad m−2 towards the pulsar. The brightest of these pulses is ∼60 per cent linearly polarized but the pulse-to-pulse variability in the polarization fraction is significant. We find that the cumulative GP flux distribution follows a power-law distribution with index −2.75 ± 0.02. Although the detected GPs make up only ∼10 per cent of the mean flux, their average pulse shape is indistinguishable from the integrated pulse profile, and we postulate that, unlike in the Crab pulsar, there are no additional regular emission components. The pulses are scattered at L-band frequencies with the brightest pulse exhibiting a scattering time-scale of τ = 0.92 ± 0.02 ms at 1.2 GHz. We find several of the giants display very narrow-band flux knots similar to those seen in many Fast Radio Bursts, which we assert cannot be due to scintillation or plasma lensing. The GP time-of-arrival distribution is found to be Poissonian on all but the shortest time-scales where we find four GPs in six rotations, which if GPs are statistically independent is expected to occur in only 1 of 7000 observations equivalent to our data.

Enhanced x-ray emission coinciding with giant radio pulses from the Crab Pulsar.

Giant radio pulses (GRPs) are sporadic bursts emitted by some pulsars that last a few microseconds and are hundreds to thousands of times brighter than regular pulses from these sources. The only GRP-associated emission outside of radio wavelengths is from the Crab Pulsar, where optical emission is enhanced by a few percentage points during GRPs. We observed the Crab Pulsar simultaneously at x-ray and radio wavelengths, finding enhancement of the x-ray emission by 3.8 ± 0.7% (a 5.4σ detection) coinciding with GRPs. This implies that the total emitted energy from GRPs is tens to hundreds of times higher than previously known. We discuss the implications for the pulsar emission mechanism and extragalactic fast radio bursts.

X-rays from giant radio pulses

X-rays from giant radio pulses

Numerical simulation of a laser with a Q-switched cavity for production of ultrashort pulses

A theoretical model was developed to calculate lasing modes for giant pulses in solid-state lasers with Q-switched cavities. The lasing process begins with steady-state mode locking. Then, when a control pulse is fed to the cavity electro-optic modulator, the light propagating in the cavity is amplified. When the laser pulse reaches maximum energy, the cavity opens, producing a single ultrashort pulse. Simulations performed using a commercial 50 W Nd:YAG solid-state CW laser diode pump module indicated that, when the driver parameters for the electro-optical modulator are optimized, the cavity switching mode can be used for high-efficiency extraction of almost all the energy (up to 20 mJ) stored in the laser medium in steady-state mode in the form of a single pulse with a duration in the hundreds of picoseconds.

Fast radio burst detection in the presence of coloured noise

ABSTRACT In this paper, we investigate the impact of correlated noise on fast radio burst (FRB) searching. We found that (1) the correlated noise significantly increases the false alarm probability; (2) the signal-to-noise ratios (S/N) of the false positives become higher; (3) the correlated noise also affects the pulse width distribution of false positives, and there will be more false positives with wider pulse width. We use 55-h observation for M82 galaxy carried out at Nanshan 26m radio telescope to demonstrate the application of the correlated noise modelling. The number of candidates and parameter distribution of the false positives can be reproduced with the modelling of correlated noise. We will also discuss a low S/N candidate detected in the observation, for which we demonstrate the method to evaluate the false alarm probability in the presence of correlated noise. Possible origins of the candidate are discussed, where two possible pictures, an M82-harboured giant pulse and a cosmological FRB, are both compatible with the observation.

A Sustainable Slit Jet FTIR Spectrometer for Hydrate Complexes and Beyond

Fourier transform infrared (FTIR) absorption spectroscopy of cold molecules and clusters in supersonic slit jet expansions complements and extends more sensitive action spectroscopy techniques and provides important reference data for the latter. We describe how its major drawback, large substance and carrier gas consumption, can be alleviated by one to two orders of magnitude via direct and continuous recycling of the gas mixture. This is achieved by a combination of dry rotary lobe and screw pump compression. The signal-to-noise ratio is boosted by the established buffered giant gas pulse technique with full interferogram synchronization. The buildup of water impurities typically limits the recycling gain, but is turned into a feature for the study of hydrate complexes of volatile molecules. Continuous operation with a single gas filling over several days becomes practical and useful. Decadic absorbances in the low ppm range are detectable and the mid infrared range can be recorded simultaneously with the near infrared. The less straightforward hydration number assignment of spectral features in direct absorption spectroscopy is supported by a gradual water buildup at a rate of less than 0.5 mg/h. A recent reassignment proposal for the water dimer OH stretching spectrum is refuted and vibrational spectra of vacuum-isolated 18O-water clusters are presented for the first time. Methanol docking on asymmetric ketones is used to illustrate the advantages and limitations of the recycling concept. Previous assignments of the hydrate complex of 1-phenylethanol are confirmed. Additional features of the setup await testing and refinement, but the recycling technique already substantially widens the applicability of direct absorption spectroscopy of neutral molecular clusters. It may be attractive for other high-throughput jet spectrometers.

Pulse energy distribution for RRAT J0139+33 according to observations at the 111 MHz frequency

Using five-year-monitoring observations, we carried out a blind search for pulses for rotating radio transient (RRAT) J0139+33 and PSR B0320+39. At the interval ±1.5m of the time corresponding to the source passing through the meridian, we detected 39377 individual pulses for the pulsar B0320+39 and 1013 pulses for RRAT J0139+33. The share of registered pulses from the total number of observed periods for the pulsar B0320+39 is 74%, and for the transient J0139+33 it is 0.42%. The signal-to-noise ratio (S/N) for the strongest registered pulses is, approximately, the following: S/N = 262 (for B0320+39) and S/N = 154 (for J0139+33). We obtained distributions of the number of detected pulses in S/N units for the pulsar and for the rotating transient. The distributions could be approximated with lognormal and power dependences. For the B0320+39 pulsar, the dependence is lognormal, and it turns into a power dependence at high values of S/N; and for RRAT J0139+33, the distribution of pulses by energy is described by a broken (bimodal) power dependence with an exponent of about 0.4 and 1.8 (S/N ≤ 19 and S/N ≥ 19). We did not detect a regular (pulsar) emission of J0139+33. Analysis of the obtained data suggests that RRAT J0139+33 is a pulsar with giant pulses.

Are pulsar giant pulses induced by re-emission of cyclotron resonance absorption?

It is conjectured that coherent re-emission of cyclotron resonance absorption could result in pulsar giant pulses. This conjecture seems reasonable as it can naturally explain the distribution of pulsars with giant pulses on the P- diagram.

A novel model for lasing cavities in the presence of population inversion: Bifurcation and stability analysis

Very recently a discrete model for laser cavities in an external field, in the presence of population inversion PI, was developed. Here, a model where attention is focused to a discrete PI, with gain or loss, is presented. The continuum model is constructed. The behavior of the field intensity and the PI is investigated. This is done by obtaining the exact solutions of the model equation by using the unified method. We think that this main objective of this work, which we think that it is completely new. The homogeneous equilibrium states HESs are determined and the bifurcation against the relevant parameters is analyzed qualitatively. Further the stability analysis of the HESs against in homogeneous perturbation near these states, is studied quantitatively, via solving the eigenvalue problems. It is shown that the wave intensity and the PI shows set on of giant pulses formation (or Q-swithing). Which depends on pulse duration, pulse energy, frequency and pumping rate. High power laser pulses are observed. The pulse duration is estimated. It is shown that the holding beam amplitude, the dispersion coefficient and the carrier pumping rate play significant roles on the number of the emitted photons.

A Single-pulse Study of PSR J1022+1001 Using the FAST Radio Telescope

Abstract Using the Five-hundred-meter Aperture Spherical radio Telescope (FAST), we have recorded ∼105 single pulses from PSR J1022+1001. We studied the polarization properties, their energy distribution, and their times of arrival. This is only possible with the high sensitivity available using FAST. There is no indication that PSR J1022+1001 exhibits giant pulse, nulling, or traditional mode changing phenomena. The energy in the leading and trailing components of the integrated profile is shown to be correlated. The degree of both linear and circular polarization increases with the pulse flux density for individual pulses. Our data indicates that pulse jitter leads to an excess noise in the timing residuals of 67 ns when scaled to one hour, which is consistent with Liu et al. We have unsuccessfully trialed various methods to improve timing precision through the selection of specific single pulses. Our work demonstrates that FAST can detect individual pulses from pulsars that are observed in order to detect and study gravitational waves. This capability enables detailed studies, and parameterization, of the noise processes that affect the sensitivity of a pulsar timing array.