Giant Pulses Research Articles

Measurements of the Crab Pulsar’s Giant Radio Pulse Amplitude Power-law Index Using Low-frequency Arecibo and Green Bank Telescope Observations

We report two low-frequency measurements of the power-law index for the amplitudes of giant radio pulses from the Crab pulsar. The two observations were taken with the Arecibo and Green Bank radio telescopes at center frequencies of 327 MHz and 350 MHz, respectively. We find best-fit values for the differential power-law index β (where and S is the pulse amplitude) of −2.63 ± 0.05 and −3.6 ± 0.5 from the Arecibo and Green Bank data sets, respectively. Both values are broadly consistent with other values previously measured for the Crab pulsar at low radio frequencies. These reported values may be useful in future giant pulse studies of the Crab pulsar.

Giant isolated half-cycle attosecond pulses generated in coherent bremsstrahlung emission regime.

Giant half-cycle attosecond pulse generation in the coherent bremsstrahlung emission regime is proposed for laser pulses with normal incidence on a double-foil target, where the first foil is transparent and the second foil is opaque. The presence of the second opaque target contributes to the formation of a relativistic flying electron sheet (RFES) from the first foil target. After the RFES has passed through the second opaque target, it is decelerated sharply, and bremsstrahlung emission occurs, which results in the generation of an isolated half-cycle attosecond pulse having an intensity of ∼1.4×10^{22}W/cm^{2} and a duration of 3.6as. The generation mechanism does not require extra filters and may open a regime of nonlinear attosecond science.

Resolving the Emission Regions of the Crab Pulsar’s Giant Pulses. II. Evidence for Relativistic Motion

The Crab Pulsar is the prime example of an emitter of giant pulses. These short, very bright pulses are thought to originate near the light cylinder, at ∼1600 km from the pulsar. The pulsar’s location inside the Crab Nebula offers an unusual opportunity to resolve the emission regions, using the nebula, which scatters radio waves, as a lens. We attempt to do this using a sample of 61,998 giant pulses found in coherently combined European VLBI network observations at 18 cm. These were taken at times of relatively strong scattering and hence good effective resolution. From correlations between pulse spectra, we show that the giant pulse emission regions are indeed resolved. We infer apparent diameters of ∼2000 and ∼2400 km for the main and interpulse components, respectively, and show that with these sizes the correlation amplitudes and decorrelation timescales and bandwidths can be understood quantitatively, both in our observations and in previous ones. Using pulse-spectra statistics and correlations between polarizations, we also show that the nebula resolves the nanoshots that comprise individual giant pulses. The implied diameters of ∼1100 km far exceed light-travel-time estimates, suggesting the emitting plasma is moving relativistically, with γ ≃ 104, as inferred previously from drifting bands during the scattering tail of a giant pulse. If so, the emission happens over a region extended along the line of sight by ∼107 km. We conclude that relativistic motion likely is important for producing giant pulses, and may be similarly for other sources of short, bright radio emission, such as fast radio bursts.

Analysis of the Parameters of Radio Pulsars with Giant Pulses Using the Principal Component Analysis

Clustering of radio pulsars with observable giant pulses (GPs) has been carried out using the principal component analysis. Five parameters were used (period, its derivative, observed luminosity, kinematic age, and the angle between the rotation axis and the magnetic moment of the central neutron star). It was shown that the set of all known GP pulsars is divided into two clusters in the phase space of the principal components. One of the clusters contains four pulsars with short periods and high luminosity; the second cluster contains nine long-period and fainter sources. A separate object, not included in these two clusters, is the pulsar in the Crab Nebula. Possible models that could explain the observed difference between GP pulsars were considered.

Single Pulse Studies of PSR B0950+08 with FAST

We report detailed polarization and single-pulse studies of PSR B0950+08 with the Five-hundred-meter Aperture Spherical Radio Telescope (FAST) at 1250 MHz. Significant bridge emission was observed between the inter-pulse and the main pulse and the height of the bridge decreased with increase in frequency. Our results support the interpretation that both the inter-pulse and the main pulse of this pulsar are from the same magnetic pole. From the relative peak flux density and the relative energy distribution, we conclude that no giant pulse was detected in PSR B0950+08. Our results provide opportunities to study the origin of the emission from PSR B0950+08 and offer new insights into the origins of pulsar emission and bridge emission.

Compact acousto-optical Q-switched Yb:ScBO3 laser with giant pulse energy.

In this Letter, a continuous-wave Yb:ScBO3 laser was enhanced with a maximum output power of 1.63 W and a slope efficiency of 48.97%, pumped by a continuous-wave 965 nm diode laser. Subsequently, the first, to the best of our knowledge, acousto-optically Q-switched Yb:ScBO3 laser was realized with an output wavelength of 1022 nm and repetition rates ranging from 0.04 to 1 kHz. The characteristics of pulsed lasers modulated by a commercial acousto-optic Q switcher were comprehensively demonstrated. With a low repetition rate of 0.05 kHz, the pulsed laser was generated under an absorbed pump power of 2.62 W, having an average output power of 0.44 W and giant pulse energy of 8.80 mJ. The pulse width and peak power were 80.71 ns and 109 kW, respectively. The findings manifest that the Yb:ScBO3 crystal is a gain medium with great potential for Q-switched laser generation with high pulse energy.

Probing the New Generation Geodetic Radio Telescopes for FRB Observations

We investigate the possibility of fast radio burst (FRB) observation on new special geodetic 13[Formula: see text]m wideband radio telescopes in Very Large Base Interferometry (VLBI) and single-dish modes. The Crab Pulsar Giant Pulses (GPs) were used as a reference source of FRB. In order to verify our results we use joint simultaneous observations with 32[Formula: see text]m legacy and 13[Formula: see text]m new VLBI Global Observing System (VGOS) radio telescopes of the Quasar VLBI network in the L and S/X frequency bands. The special observation session contains two 10-min scans of Crab Pulsar. We successfully detect a total of 712 pulses with flux density [Formula: see text][Formula: see text]Jy at 1653.5[Formula: see text]MHz on 32-m antenna and 262 pulses with flux density [Formula: see text][Formula: see text]Jy at 2406.3[Formula: see text]MHz on 13-m antenna in Badary observatory. The VLBI fringes were obtained for approximately every third pulse. The energy distribution of detected pulses has a break in the power law fit at [Formula: see text] and [Formula: see text]-values are [Formula: see text]0.2 and [Formula: see text]1.8 for lower and higher energies. A GP with a fluence of the order of 190[Formula: see text][Formula: see text] in L-band was detected and 48[Formula: see text][Formula: see text] in S-band. We found that the peak coincidence of right and left circular polarizations of dedispersed data on a single antenna can provide a maximum detection rate with fixed false probability. It was shown that the best GP detection rate on 13[Formula: see text]m VGOS radio telescope was achieved at Badary observatory with 13 pulses per minute in the S-band.

Achieving high pulse charge–discharge energy storage properties and temperature stability of (Ba0.98-xLi0.02Lax)(Mg0.04Ti0.96)O3 lead-free ceramics via bandgap and defect engineering

A novel dual priority strategy of strengthening charge compensation in A-site of perovskite structure and widening bandgap width was designed to prepare (Ba0.98-xLi0.02Lax)(Mg0.04Ti0.96)O3 (BLLMTx) ceramics, which can solve the conflict between polarization and breakdown strength, and improve the pulse energy storage performance of the BaTiO3-based system. As a result, ultrahigh discharge energy density of 3.98 J/cm3 and giant pulse power density of 321.6 MW/cm3 with current density of 2786.4 A/cm2 are obtained at 360 kV/cm for the (Ba0.94Li0.02La0.04)(Mg0.04Ti0.96)O3 (BLLMT0.04) ceramics with considerable fast discharge rate and outstanding temperature stability as well as cycle life, correlating with multi-ferroelectric phases coexistence, increasing bandgap width, strengthening charge compensation and establishing small size of the polar nano-regions (PNRs), which exceeds the great mass of reported lead-free ceramics. The comprehensive properties indicate that the BLLMT0.04 ceramics present potential application in pulse energy storage system. The concept of composition design via increasing bandgap width and strengthening charge compensation provides a new idea for developing lead-free dielectric ceramic capacitors.

Low-frequency observations of giant pulses from ordinary pulsars

ABSTRACTWe present the results of an investigation of the giant radio pulse (GRP) generation rate from five radio pulsars (B0301+19, B0950+08, B1112+50, B1133+16, and B1237+25) and anomalous intensity pulse generation rate from B0809+74. All data used were obtained with the Large Phased Array radio telescope at the Pushchino Radio Astronomy Observatory at 111 MHz from 2012 to 2021. In addition to the analysis of the rate of generation of bright pulses, we analyse the distribution of bright pulses in the phase of the pulsar period and search for clusters of bright pulses – several bright pulses emitted in adjacent pulsar periods. It is found that pulsars B0301+19, B1112+50, B1133+16, and B1237+25 demonstrate different generation rates and generation of clusters. Pulsar B1112+50 generates GRP clusters more often than the other pulsars studied. The longest cluster of GRPs containing four single pulses is detected from this pulsar. GRPs from the pulsars studied are distributed along the longitudes of the main components of the average pulses of these pulsars. This distribution is 1.5–2 times narrower than the phase distribution of non-giant pulses. It is found that the distance between the components of the average GRP profile and the distance between the components of the average non-giant profile differ substantially for pulsars with multicomponent average profiles.

On Single-pulse Energies of Some Bright Pulsars Observed at 1.7 GHz

Abstract We present Arecibo observations of the bright pulsars B0301+19, B0525+21, B0540+23, B0611+22, and B0823+26 at 1.7 GHz with 100 MHz bandwidth. No giant pulses were found, except for B0823+26, where we recorded a giant interpulse with 230 times the average peak intensity. The postcursor in B0823+26 shows a symmetric double-peaked structure, indicating that it is frequency dependent. In all pulsars, for a given single-pulse peak intensity there is a range of equivalent widths up to a maximum, which becomes smaller the stronger the pulses are, thereby apparently limiting the energy output. Forming average profiles from pulses with certain equivalent widths leads to profiles with changing component characteristics and could allow exploring the magnetosphere at different heights, assuming a dipolar field geometry. We found that the normalized lag-1 autocorrelation coefficient for single-pulse energies can be over 0.5, indicating high correlations. From the first peak of the energy autocorrelation function a so-far-unobserved 15-period modulation is found for B0540+23, as well as a possible 10-period modulation for B0611+22. We also show that a fit of the Weibull distribution to the cumulative probability for the energies yields a better fit than the usual lognormal distribution. The cumulative probability distributions permit an estimate of the nulling fraction, which ranges from 0.6% for B0611+22 to 24% for B0525+21.

Dual-frequency single-pulse study of PSR B0950+08

PSR B0950+08 is a bright nonrecycled pulsar whose single-pulse fluence variability is reportedly large. Based on observations at two widely separated frequencies, 55 MHz (NenuFAR) and 1.4 GHz (Westerbork Synthesis Radio Telescope), we review the properties of these single pulses. We conclude that they are more similar to ordinary pulses of radio emission than to a special kind of short and bright giant pulses, observed from only a handful of pulsars. We argue that a temporal variation of the properties of the interstellar medium along the line of sight to this nearby pulsar, namely the fluctuating size of the decorrelation bandwidth of diffractive scintillation makes an important contribution to the observed single-pulse fluence variability. We further present interesting structures in the low-frequency single-pulse spectra that resemble the “sad trombones” seen in fast radio bursts (FRBs); although for PSR B0950+08 the upward frequency drift is also routinely present. We explain these spectral features with radius-to-frequency mapping, similar to the model developed by Wang et al. (2019, ApJ, 876, L15) for FRBs. Finally, we speculate that μs-scale fluence variability of the general pulsar population remains poorly known, and that its further study may bring important clues about the nature of FRBs.

Passively Q-switched 5-µm Ce3+-doped selenide glass laser using Fe:CdTe and Fe:CdSe as saturable absorbers.

The first, to the best of our knowledge, mid-infrared Q-switched Ce3+-doped glass laser is demonstrated. As saturable absorbers, Fe2+:CdSe and Fe2+:CdTe are used for the first time. When Q-switched by Fe:CdSe, the laser operates in a multi-pulse regime with an individual pulse width of 110 ns, centered at λ = 5.20 µm. With Fe:CdTe as saturable absorber, 1-3 giant pulses of 30 ns pulse width are generated at λ = 5.13 µm.

Coronal Density Measurements Using Giant Radio Pulses of the Crab Pulsar at the Cycle 24/25 Minimum

Accurate measurements of the coronal plasma density profile, which varies with the solar cycle (SC), are necessary to elucidate the solar wind acceleration. In this study, the Crab pulsar is observed using the 327 MHz radio telescope at the Toyokawa Observatory of the Institute for Space-Earth Environmental Research of Nagoya University to investigate the coronal plasma density profile for radial distances between 5 and 60 solar radii at the SC24/25 minimum. We derive the dispersion measures (DMs) that represent the integration of plasma density along the line of sight (LOS) for giant radio pulses of the Crab pulsar. We find that the observed DMs increased above the interstellar background level when the LOS for the Crab pulsar approached the Sun in mid-June 2018 and 2019. This increase in DM is attributed to the effect of the coronal plasma. We determine the plasma density distribution by fitting a spherically symmetric model to the observed DM data. The flat radial slopes of the best-fit model are consistent with pulsar observations in the low-activity periods of past SCs, and they are attributed to the effect of the coronal hole over the south pole of the Sun. Our results show that the density level near the Sun is similar to those observed in the low activity periods of past SCs, implying recovery of the coronal plasma density from a significant reduction at the SC23/24 minimum.

Generation, amplification and compression of wave packets with a large depth of phase modulation: the formation of giant optical pulses such as stray waves or rogue waves

Generation, amplification and compression of wave packets with a large depth of phase modulation: the formation of giant optical pulses such as stray waves or rogue waves

Implications of a rapidly varying FRB in a globular cluster of M81

ABSTRACT A repeating source of fast radio bursts (FRBs) is recently discovered from a globular cluster of M81. Association with a globular cluster (or other old stellar systems) suggests that strongly magnetized neutron stars, which are the most likely objects responsible for FRBs, are born not only when young massive stars undergo core-collapse, but also by mergers of old white dwarfs. We find that the fractional contribution to the total FRB rate by old stellar populations is at least a few per cent, and the precise fraction can be constrained by FRB searches in the directions of nearby galaxies, both star-forming and elliptical ones. Using very general arguments, we show that the activity time of the M81-FRB source is between 104 and 106 yr, and more likely of the order of 105 yr. The energetics of radio outbursts put a lower limit on the magnetic field strength of 10$^{13}\,$G, and the spin period $\gtrsim 0.2\,$s, thereby ruling out the source being a milli-second pulsar. The upper limit on the persistent X-ray luminosity (provided by Chandra), together with the high FRB luminosity and frequent repetitions, severely constrains (or rules out) the possibility that the M81-FRB is a scaled-up version of giant pulses from Galactic pulsars. Finally, the 50-ns variability time of the FRB light curve suggests that the emission is produced in a compact region inside the neutron star magnetosphere, as it cannot be accounted for when the emission is at distances $\gtrsim 10^{10}\rm \, cm$.

Search for Dispersed Pulses at Declinations from +56° to +87°

The survey of northern hemisphere were made at a frequency of 111 MHz. The total accumulation time at each point of the sky was at least one hour. 75 sources of pulse emission were detected. More then 80% of these sources are known pulsars observed in the side lobes of the antenna. From one to several hundreds pulses were detected in twelve known pulsars. For four pulsars (J0157+6212, J1910+5655, J2337+6151, J2354+6155) the narrowness of the strongest pulses and the ratio of peak flux densities in the strongest pulse and in the average profile indicate that they can be pulsars with giant pulses. One new rotating radio transient (RRAT) J0812+8626 with a dispersion measure DM=40.25 pc/cm3 was detected.

Radio and X-ray observations of giant pulses from XTE J1810 − 197

ABSTRACT We present the results of two years of radio and X-ray monitoring of the magnetar XTE J1810 − 197 since the radio re-activation in late 2018. Single pulse analysis of radio observations from the Lovell and MkII telescopes at 1564 MHz and the Effelsberg telescope at 6 GHz has resulted in the detection of a total of 91 giant pulses (GPs) between MJDs 58858 and 59117. These GPs appear to be confined to two specific phase ranges (0.473 ≤ ϕ ≤ 0.502 and 0.541 ≤ ϕ ≤ 0.567). We also observe that the first detection of GP emission corresponds to a minimum in the spin-down rate. Simultaneous radio and X-ray observations were performed on MJDs 59009 and 59096. The 0.5–10 keV X-ray spectrum from NICER is well characterized by a two-component blackbody model that can be interpreted as two hot spots on the polar cap of the neutron star. The blackbody temperature decreases with time, consistent with the previous outburst, while the change in the pulsed fraction does not follow the same trend as was seen in the previous outburst. The radio and X-ray flux of XTE J1810 − 197 are correlated during the initial phase of the outburst (MJD 58450 – MJD 58550) and an increase in the radio flux is observed later that may be correlated to the onset of GPs. We argue that the disparity in the evolution of the current outburst compared to the previous one can be attributed to a change in geometry of the neutron star.

Comparison of Terrestrial and Lunar Time Scales by Giant Pulsar Impulses

We have developed a model for the time delay of pulse arrival between stations on the Moon and Earth. Comparison of the lunar and terrestrial time scales is proposed to be carried out by comparing the arrival time moments of giant pulses from pulsars. A method for such a comparison has been developed based on the cross-correlation analysis of the received pulses. Using the example of giant pulses from the pulsar PSR 0531+21, we showed that the error of comparing scales in the case of a high signal-to-noise ratio reaches a sub-discrete level and, thus, is determined by the reception band of the recording equipment.

Ultra-wideband, Multiepoch Radio Study of the First Discovered “Main-sequence Radio Pulse Emitter” CU Vir

Abstract The presence of a large-scale surface magnetic field in early-type stars leads to several unique electromagnetic phenomena producing radiation over X-ray to radio bands. Among them, the rarest type of emission is electron cyclotron maser emission (ECME) observed as periodic, circularly polarized radio pulses. The phenomenon was first discovered in the hot magnetic star CU Vir. Past observations of this star led to the consensus that the star produces only right circularly polarized ECME, suggesting that only one magnetic hemisphere takes part in the phenomenon. Here we present the first ultra-wideband (0.4–4 GHz) study of this star using the upgraded Giant Metrewave Radio telescope and the Karl G. Jansky Very Large Array, which led to the surprising discovery of ECME of both circular polarizations up to around 1.5 GHz. The GHz observations also allowed us to infer that the upper ECME cutoff frequency is at ≳5 GHz. The sub-GHz observation led to the unexpected observation of more than two pairs of ECME pulses per rotation cycle. In addition, we report the discovery of a “giant pulse” and transient enhancements, which are potentially the first observational evidence of “centrifugal breakout” of plasma from the innermost part of the stellar magnetosphere. The stark contrast between the star’s behavior at GHz and sub-GHz frequencies could either be due to propagation effects, a manifestation of varying magnetic field topology as a function of height, or a signature of an additional “ECME engine.”

Investigation of the properties of four rotating radio transients at 111 MHz

ABSTRACT We present an analysis of the individual pulses of four rotating radio transients (RRATs), previously discovered in a monitoring survey running for 5.5 yr at the frequency of 111 MHz. At a time interval equivalent to 5 d of continuous observations for each RRAT, 90, 389, 206 and 157 pulses were detected in J0640+07, J1005+30, J1132+25 and J1336+33, respectively. The investigated RRATs have different distributions of their pulse amplitudes. For J0640+07 and J1132+25, the distribution is described by a single exponent over the entire range of flux densities. For J1005+30 and J1336+33, it is a lognormal function with a power-law tail. For J0640+07 and J1005+30, we have detected pulses with a signal-to-noise ratio (S/N) of a few hundred. For J1132+25 and J1336+33, the S/N of the strongest pulses reaches several tens. These RRATs show a strong change in their emission. When the strengths of their pulse amplitudes are significantly changed, we see long intervals of absence of emission or its strong attenuation. The analysis carried out in this work shows that it is possible that all the studied RRATs are, apparently, pulsars with giant pulses.