The “Bi-drifting” subpulses of PSR J0815+0939 observed with the Five-hundred-meter Aperture Spherical radio Telescope

We report the “Bi-drifting” subpulses observed in PSR J0815+0939 using the Five-hundred-meter Aperture Spherical radio Telescope (FAST). The observation at band from 1050-1450MHz is evenly divided into two bands, i.e., the bands at center frequencies 1150MHz and 1350 MHz. The mean pulse profiles and the “Bi-drifting” subpulses at this two bands are investigated. It is found that the pulse profiles at this two frequencies show four emission components, and the peak separations between four emission components decrease with the increase of frequency. In addition, the ratio of peak intensity of each component to the intensity of component IV at 1150MHz is larger than that at 1350 MHz. We carry out an analysis of the longitude-resolved fluctuation spectrum and two-dimensional fluctuation spectrum for each emission component, and find that the P3 of components I, II and III are about 10.56, 10.57 and 10.59 s at 1150MHz and 1350 MHz. However, the reliable measurements of P3 of component IV and P2 for these four components were not obtained due to the low signal-to-noise ratio of observation data. The pulse energy distributions at frequencies 1150 and 1350MHz are presented, and it is found that no nulling phenomenon have been found in this pulsar. With our observation from the FAST, the “Bi-drifting” subpulse phenomenon of PSR J0815+0939 is expanded from 400MHz to 1350 MHz, which is helpful for the relevant researchers to test and constrain the pulsar emission model, especially the model of “Bi-drifting” subpulse.

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.

A statistical analysis of the nulling pulsar population

ABSTRACT Approximately 8 per cent of the ∼2800 known pulsars exhibit ‘nulling,’ a temporary broad-band cessation of normal pulsar emission. Nulling behaviour can be coarsely quantified by the nulling fraction, which describes the percentage of time a given pulsar will be found in a null state. In this paper, we perform the most thorough statistical analysis thus far of the properties of 141 known nulling pulsars. We find weak, non-linear correlations between nulling fraction and pulse width, as well as nulling fraction and spin period which could be attributed to selection effects. We also further investigate a recently hypothesized gap at 40 per cent nulling fraction. While a local minimum does exist in the distribution, we cannot confirm a consistent and unique break in the distribution when we investigate with univariate and multivariate clustering methods, nor can we prove the existence of two statistically distinct populations about this minimum. Using the same methods, we find that nulling pulsars are a statistically different population from normal, radio, non-nulling pulsars, which has never been quantitatively verified. In addition, we summarize the findings of the prior nulling pulsar statistics literature, which are notoriously contradictory. This study, in context, furthers the idea that nulling fraction alone does not contain enough information to describe the behaviour of a nulling pulsar and that other parameters such as null lengths and null randomness, in addition to a better understanding of selection effects, are required to fully understand this phenomenon.

Radio and high-energy emission of pulsars revealed by general relativity

Context. According to current pulsar emission models, photons are produced within their magnetosphere and current sheet, along their separatrix, which is located inside and outside the light cylinder. Radio emission is favoured in the vicinity of the polar caps, whereas the high-energy counterpart is presumably enhanced in regions around the light cylinder, whether this is the magnetosphere and/or the wind. However, the gravitational effect on their light curves and spectral properties has only been sparsely researched. Aims. We present a method for simulating the influence that the gravitational field of the neutron star has on its emission properties according to the solution of a rotating dipole evolving in a slowly rotating neutron star metric described by general relativity. Methods. We numerically computed photon trajectories assuming a background Schwarzschild metric, applying our method to neutron star radiation mechanisms such as thermal emission from hot spots and non-thermal magnetospheric emission by curvature radiation. We detail the general-relativistic effects onto observations made by a distant observer. Results. Sky maps are computed using the vacuum electromagnetic field of a general-relativistic rotating dipole, extending previous works obtained for the Deutsch solution. We compare Newtonian results to their general-relativistic counterpart. For magnetospheric emission, we show that aberration and curvature of photon trajectories as well as Shapiro time delay significantly affect the phase delay between radio and high-energy light curves, although the characteristic pulse profile that defines pulsar emission is kept.

Detecting pulsar polarization below 100 MHz with the Long Wavelength Array

ABSTRACT Using the first station of the Long Wavelength Array (LWA1), we examine polarized pulsar emission between 25 and 88 MHz. Polarized light from pulsars undergoes Faraday rotation as it passes through the magnetized interstellar medium. Observations from low-frequency telescopes are ideal for obtaining precise rotation measures (RMs) because the effect of Faraday rotation is proportional to the square of the observing wavelength. With these RMs, we obtained polarized pulse profiles to see how polarization changes in the 25–88 MHz range. The RMs were also used to derive values for the electron-density-weighted average Galactic magnetic field along the line of sight. We present RMs and polarization profiles of 15 pulsars acquired using data from LWA1. These results provide new insight into low-frequency polarization characteristics and pulsar emission heights, and complement measurements at higher frequencies.

Pulsar polarimetry with the Parkes ultra-wideband receiver

ABSTRACT Pulsar radio emission and its polarization are observed to evolve with frequency. This frequency dependence is key to the emission mechanism and the structure of the radio beam. With the new ultra-wideband receiver (UWL) on the Parkes radio telescope we are able, for the first time, to observe how pulsar profiles evolve over a broad continuous bandwidth of 700–4000 MHz. We describe here a technique for processing broad-band polarimetric observations to establish a meaningful alignment and visualize the data across the band. We apply this to observations of PSRs J1056–6258 and J1359–6038, chosen due to previously unresolved questions about the frequency evolution of their emission. Application of our technique reveals that it is possible to align the polarization position angle (PA) across a broad frequency range when constrained to applying only corrections for dispersion and Faraday rotation to do so. However, this does not correspond to aligned intensity profiles for these two sources. We find that it is possible to convert these misalignments into emission height range estimates that are consistent with published and simulated values, suggesting that they can be attributed to relativistic effects in the magnetosphere. We discuss this work in the context of the radio beam structure and prepare the ground for a wider study of pulsar emission using broad-band polarimetric data.

K-means Clustering-based Radio Neutron Star Pulsar Emission Mechanism

: The aim of this paper is to work on K-means clustering-based radio neutron star pulsar emission mechanism. Background: The pulsars are a rare type of neutron star that produces radio rays. Such type of rays are detectable on earth and it attracts scientists because of its concern with space-time, interstellar medium, and states of matter. During the rotation of pulsar rays, it emits the rays in the whole sky and after crossing the threshold value, the pattern of radio emission broadband detected. As rotation speed of pulsar increases then accordingly the types of the pattern produced periodically. Every pulsar emits different patterns which are a little bit different from each other which is fully depends on its rotation. The detected signals are known as a candidate. Its length of observation can determine it and it is average of all rotation of pulsar. Objective: The main objectives of this radio neutron star pulsar emission mechanism are: (a) Decision Tree Classifier (2) K-means Clustering (3) Neural Networks. Method: The Pulsar Emission Data was broken down into two sets of data: Training Data and Testing Data. The Training Data used to train the Decision Tree The algorithm, K-means clustering, and Neural Networks to allow it to identify, which attributes (Training Labels), are useful for identification of Neutron Pulsar Emissions. Results: The analysis is using multiple machine learning algorithms; it concluded that using neural networks is the best possible method to detect pulsar emissions from neutron stars. The best result achieved is 98% using Neural Networks. Conclusion: There are so many benefits of pulsar rays in different technology. Earth can detect pulsar ray from low orbit. Earth can completely absorb X-ray in the atmosphere and from these; we can say that the wavelength is limited to those who do not have an atmosphere like space. The result we got according to that we can say that the algorithm we used successfully used for detecting the pulsar signals.