scholarly journals A broadband radio study of PSR J0250+5854: the slowest-spinning radio pulsar known

2021 ◽  
Author(s):  
C H Agar ◽  
P Weltevrede ◽  
L Bondonneau ◽  
J-M Grießmeier ◽  
J W T Hessels ◽  
...  
Keyword(s):  
Radio Emission ◽  
Flux Density ◽  
Spectral Index ◽  
Fold Increase ◽  
Radio Pulsar ◽  
Slow Rotation ◽  
Polar Cap ◽  
Broadband Radio ◽  
Absolute Height ◽  
S Period

Abstract We present radio observations of the most slowly rotating known radio pulsar PSR J0250+5854. With a 23.5 s period, it is close, or even beyond, the P-$\dot{P}$ diagram region thought to be occupied by active pulsars. The simultaneous observations with FAST, the Chilbolton and Effelsberg LOFAR international stations, and NenuFAR represent a five-fold increase in the spectral coverage of this object, with the detections at 1250 MHz (FAST) and 57 MHz (NenuFAR) being the highest- and lowest-frequency published respectively to date. We measure a flux density of 4 ± 2 μJy at 1250 MHz and an exceptionally steep spectral index of $-3.5^{+0.2}_{-1.5}$, with a turnover below ∼95 MHz. In conjunction with observations of this pulsar with the GBT and the LOFAR Core, we show that the intrinsic profile width increases drastically towards higher frequencies, contrary to the predictions of conventional radius-to-frequency mapping. We examine polarimetric data from FAST and the LOFAR Core and conclude that its polar cap radio emission is produced at an absolute height of several hundreds of kilometres around 1.5 GHz, similar to other rotation-powered pulsars across the population. Its beam is significantly underfilled at lower frequencies, or it narrows because of the disappearance of conal outriders. Finally, the results for PSR J0250+5854 and other slowly spinning rotation-powered pulsars are contrasted with the radio-detected magnetars. We conclude that magnetars have intrinsically wider radio beams than the slow rotation-powered pulsars, and that consequently the latter’s lower beaming fraction is what makes objects such as PSR J0250+5854 so scarce.

scholarly journals On the Location of Radio and X-Ray Emission in the Algol System

1980 ◽  
Vol 88 ◽  
pp. 229-232
Author(s):  
D. R. Florkowski
Keyword(s):  
Radio Emission ◽  
Mass Loss ◽  
Flux Density ◽  
Spectral Index ◽  
Time Scale ◽  
Synchrotron Source ◽  
X Ray ◽  
Algol System

The radio behaviour of Algol at centimeter wavelengths has been reviewed by Hjellming (1976, 1977), and by Gibson (1976). The observed radio emission can be roughly divided into two types: a quiescent type and a flare-like or outburst type. The quiescent emission is characterized by a low flux density, usually between 20 − 50 mJy, and a nearly flat spectral index. The latter means that the value of the flux density is nearly independent of wavelength. The variations in flux density, when present, are gradual and have a time scale on the order of days. The flare-like behaviour shows rapid and large changes in flux density. The amplitude of an outburst is wavelength dependent, the shorter wavelengths having larger amplitudes. Woodsworth and Hughes (1976, hereafter WH) attributed the two types of behaviour to two physically distinct sources. The quiescent type of emission is produced by a very large, thermally emitting cloud which surrounds the eclipsing system. The flare-like variations are due to a synchrotron source that is associated with mass loss. Their model is inconsistent with optical and X-ray information concerning the Algol system. However, a model with two radio components can be modified to agree with other types of data.

scholarly journals Evolution of the Radio Emission from Young SNRs according to Observational Data

1979 ◽  
Vol 32 (2) ◽  
pp. 95 ◽  
Author(s):  
KS Stankevich
Keyword(s):  
Experimental Data ◽  
Radio Emission ◽  
Flux Density ◽  
Observational Data ◽  
Spectral Index ◽  
Density Measurements ◽  
The Past ◽  
Absolute Flux ◽  
Density Decrease ◽  
Frequency Variations

Results are given from a still-continuing series of absolute flux density measurements for the SNR CasA. The measurements have been taken regularly over the past 16 years at 24 wavelengths in the range 3-60 cm. New data are presented for the rate of flux density decrease, and for time and frequency variations in the spectral index. Intensity increases that are localized in frequency are described. The results are generalized in a model for the radio emission from a young SNR, and this is used to analyse experimental data for flux density decreases in the emission from 3C 10 and 58.

Particle acceleration and electromagnetic field of deformed neutron stars

2019 ◽  
Vol 35 (09) ◽  
pp. 2050056 ◽  
Author(s):  
Javlon Rayimbaev ◽  
Bobur Turimov ◽  
Figueroa Marcos ◽  
Satimbay Palvanov ◽  
Azamkhan Rakhmatov
Keyword(s):  
Magnetic Field ◽  
Particle Acceleration ◽  
Neutron Star ◽  
Neutron Stars ◽  
Electromagnetic Fields ◽  
Deformation Parameter ◽  
Radio Pulsar ◽  
Slow Rotation ◽  
Polar Cap ◽  
Surface Magnetic Field

Neutron stars (NS)s are astrophysical objects with strong gravitational and electromagnetic fields. Since there are several effects on radiation processes around the star, it is impossible to consider whole effects all together. One way to study the processes is by considering them one by one as a toy model. In this paper, we have investigated the effects of spacetime deformation on the surface magnetic field of the slowly rotating neutron star and its plasma magnetospheric processes, such as the plasma magnetosphere formation around the star. At first, the approximate vacuum solutions of the Maxwell equations for the electromagnetic fields of a magnetized neutron star in a slowly rotating deformed spacetime metric have been obtained. It has been shown that the positive deformation parameter leads to an increase in the value of the (surface) magnetic field at the near zone of the neutron star, while the effect of the negative deformation parameter is vice versa. We have also considered the electric field of the slowly rotating neutron star in the spacetime. In the slow rotation approximation, we have studied the particle acceleration in the polar cap zone, considering the effect of deformation of spacetime on the [Formula: see text]-Lorentz factor of a relativistic charged particle. It is shown that in the case of the positive deformation, an additional gravity occurs around the NS. The effects of spacetime deformation on magneto-dipolar radiation of radio pulsars and polar cap size have also been studied and shown that negative deformation of spacetime increased the radiation luminosity and as positive deformation increases, the luminosity decreases. Size of polar cap region of a neutron star, where magnetic field lines open, increases with increasing the value of the deformation parameter [Formula: see text]. Moreover, we have studied the influence of the spacetime deformation on the death line for radio pulsar, which separates the region in [Formula: see text] [Formula: see text] diagram, where the pulsar can or cannot radiate in radio band (create pair production) through inverse compton scattering (ICS). It is shown that the negative (positive) deformation shifts upward (downward) the death line, which means that even a small negative (positive) deformation of spacetime may cause to be radio-quite (be radio load) the radio pulsar which is lying on the death line (in [Formula: see text] diagram) in the GR frame with its corresponding parameters.

scholarly journals Nonstationary Phenomena in the Radiation of Young Supernova Remnants

1987 ◽  
Vol 40 (6) ◽  
pp. 801 ◽  
Author(s):  
VP Ivanov ◽  
KS Stankevich
Keyword(s):  
Radio Emission ◽  
Flux Density ◽  
Spectral Index ◽  
Supernova Remnants ◽  
Crab Nebula ◽  
Adiabatic Expansion ◽  
Cassiopeia A ◽  
Average Decrease ◽  
Tycho Brahe ◽  
The Crab Nebula

The time variation of the radio emission from the supernova remnants Cassiopeia A, the Crab Nebula and Tycho Brahe (SN 1572) is investigated. There is a frequency dependence on the rate of decrease in the flux density of Cassiopeia A for the period 1957 to 1984. The (positive) spectral index has a secular decrease and also, for frequencies above 320 MHz, slight oscillations with a six-year period. The radio emission from the Crab Nebula was constant from 1953 to 1975 but has since decreased accompanied by a change in spectral index. The average decrease of the flux density of SN 1572 from 1963 to 1983 was 0�52% per year, close to the value predicted for adiabatic expansion.

scholarly journals A circular polarization survey for radio stars with the Australian SKA Pathfinder

2021 ◽  
Vol 502 (4) ◽  
pp. 5438-5454
Author(s):  
Joshua Pritchard ◽  
Tara Murphy ◽  
Andrew Zic ◽  
Christene Lynch ◽  
George Heald ◽  
...  
Keyword(s):  
Radio Emission ◽  
Brightness Temperature ◽  
Circular Polarization ◽  
Flux Density ◽  
Wide Band ◽  
M Dwarfs ◽  
Square Kilometre Array ◽  
Population Statistics ◽  
Chemically Peculiar ◽  
Radio Stars

ABSTRACT We present results from a circular polarization survey for radio stars in the Rapid ASKAP Continuum Survey (RACS). RACS is a survey of the entire sky south of δ = +41○ being conducted with the Australian Square Kilometre Array Pathfinder telescope (ASKAP) over a 288 MHz wide band centred on 887.5 MHz. The data we analyse include Stokes I and V polarization products to an RMS sensitivity of 250 μJy PSF−1. We searched RACS for sources with fractional circular polarization above 6 per cent, and after excluding imaging artefacts, polarization leakage, and known pulsars we identified radio emission coincident with 33 known stars. These range from M-dwarfs through to magnetic, chemically peculiar A- and B-type stars. Some of these are well-known radio stars such as YZ CMi and CU Vir, but 23 have no previous radio detections. We report the flux density and derived brightness temperature of these detections and discuss the nature of the radio emission. We also discuss the implications of our results for the population statistics of radio stars in the context of future ASKAP and Square Kilometre Array surveys.

scholarly journals Simultaneous X-ray and radio observations of the transitional millisecond pulsar candidate CXOU J110926.4–650224

2021 ◽  
Vol 655 ◽  
pp. A52
Author(s):  
F. Coti Zelati ◽  
B. Hugo ◽  
D. F. Torres ◽  
D. de Martino ◽  
A. Papitto ◽  
...  
Keyword(s):  
Radio Emission ◽  
Flux Density ◽  
Millisecond Pulsar ◽  
Radio Emissions ◽  
X Ray ◽  
Link Type ◽  
Upper Limit ◽  
Variability Pattern ◽  
Average Flux ◽  
Compact Array

We present the results of simultaneous observations of the transitional millisecond pulsar (tMSP) candidate CXOU J110926.4–650224 with the XMM-Newton satellite and the MeerKAT telescope. The source was found at an average X-ray luminosity of LX ≃ 7 × 1033 erg s−1 over the 0.3−10 keV band (assuming a distance of 4 kpc) and displayed a peculiar variability pattern in the X-ray emission, switching between high, low and flaring modes on timescales of tens of seconds. A radio counterpart was detected at a significance of 7.9σ with an average flux density of ≃33 μJy at 1.28 GHz. It showed variability over the course of hours and emitted a ≃10-min long flare just a few minutes after a brief sequence of multiple X-ray flares. No clear evidence for a significant correlated or anticorrelated variability pattern was found between the X-ray and radio emissions over timescales of tens of minutes and longer. CXOU J110926.4–650224 was undetected at higher radio frequencies in subsequent observations performed with the Australia Telescope Compact Array, when the source was still in the same X-ray sub-luminous state observed before, down to a flux density upper limit of 15 μJy at 7.25 GHz (at 3σ). We compare the radio emission properties of CXOU J110926.4–650224 with those observed in known and candidate tMSPs and discuss physical scenarios that may account for its persistent and flaring radio emissions.

scholarly journals A Catalogue of Galactic Radio Sources

1968 ◽  
Vol 21 (3) ◽  
pp. 369 ◽  
Author(s):  
MJL Kesteven
Keyword(s):  
Flux Density ◽  
Spectral Index ◽  
Galactic Plane ◽  
Radio Sources ◽  
Galactic Radio

The results of a survey of radio sources in the galactic plane in the longitude range 1800 to 400 with the 1 mile Molonglo Cross telescope at 408 MHz are presented. The methods of observation and reduction are described briefly. The catalogue lists the position, flux density, size, and spectral index for 80 sources

scholarly journals Ha, ha, ha, ha, staying alive, staying alive: A radio pulsar with an 8.5-s period challenges emission models

2000 ◽  
Vol 177 ◽  
pp. 185-188 ◽  
Author(s):  
M. D. Young ◽  
R. N. Manchester ◽  
S. Johnston
Keyword(s):  
Magnetic Field ◽  
Equation Of State ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Pair Creation ◽  
Radio Pulsar ◽  
Radio Waves ◽  
Long Period ◽  
Emission Models ◽  
S Period

AbstractWe report the discovery of the longest known radio pulsar period. PSR J2144–3933, previously thought to have a period of 2.84 s, actually has a period of 8.51 s. Under the usual assumptions about the stellar equation of state, this pulsar has an average surface dipolar magnetic field strength of ~ 2.0 × 1012G. According to popular theories of the emission mechanism this pulsar should not be emitting radio waves because its long period and magnetic field strength make pair creation impossible for all reasonable magnetic field configurations. Either assumptions about the equation of state are incorrect, or the emission theories must be revised.

scholarly journals A model of an ion-proton radio pulsar polar cap

2019 ◽  
Author(s):  
P B Jones
Keyword(s):  
Neutron Star ◽  
Surface Temperature ◽  
Emission Mechanism ◽  
Polar Cap ◽  
Ion Proton ◽  
S Period ◽  
Basic Equations ◽  
Radio Transients ◽  
Star Surface ◽  
Rotating Radio Transients

Abstract A number of previous papers have developed an ion-proton theory of the pulsar polar cap. The basic equations summarizing this are given here with the results of sets of model step-to-step calculations of pulse-precursor profiles. The nature of step-to-step profile variations is described by calculated phase-resolved modulation indices. The conditions under which nulls are present in step sequences are analysed. The change of mean null length with neutron-star surface temperature shows a pathway ending in emission similar to the Rotating Radio Transients. The model accommodates exceptional pulsars, the millisecond pulsars (in principle), and the 8.5 s period PSR J2144-3933. These are considered separately and their emission mechanism discussed in some detail.

scholarly journals Non-thermal radio emission in Wolf-Rayet stars: is binarity a pre-requisite?

1999 ◽  
Vol 193 ◽  
pp. 348-349
Author(s):  
Sean M. Dougherty
Keyword(s):  
Radio Emission ◽  
Spectral Index ◽  
Thermal Emission ◽  
Radio Observations ◽  
Thermal Radio ◽  
Thermal Radio Emission ◽  
Thermal Emitters

Radio observations of Wolf-Rayet stars currently available in the literature are examined to determine whether binarity is a common feature of WR systems with non-thermal emission. Among 24 stars with observed spectral index values, seven are definite non-thermal emitters, and six others possibly have composite thermal/non-thermal spectra. Stellar companions have been identified in 71% of the non-thermal emitters, strongly supporting a link between non-thermal emission and binarity.

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