scholarly journals Pulsar emission at the bottom end of the electromagnetic spectrum

2012 ◽  
Vol 8 (S291) ◽  
pp. 317-320 ◽  
Author(s):  
Vladislav Kondratiev ◽  
Keyword(s):  
Low Frequency ◽  
Single Pulse ◽  
Spectral Width ◽  
Electromagnetic Spectrum ◽  
Fractional Bandwidth ◽  
Pulsar Emission ◽  
Pulsar Radio ◽  
Giant Pulses ◽  
Decameter Radio ◽  
Pulsar Radio Emission

AbstractPulsars are arguably the only astrophysical sources whose emission spans the entire electromagnetic spectrum, from decameter radio wavelengths to TeV energies. The LOw Frequency ARray (LOFAR) offers the unique possibility to study pulsars over a huge fractional bandwidth in the bottom 4 octaves of the radio window, from 15–240 MHz. Here we present a LOFAR study of pulsar single pulses, focussing specifically on the bright nearby pulsar B0809+74. We show that the spectral width of bright low-frequency pulses can be as narrow as 1 MHz and scales with increasing frequency as Δ f/fc ~ 0.15, at least in the case of the PSR B0809+74. This appears to be intrinsic to the pulsar, as opposed to being due to propagation effects. If so, this behavior is consistent with predictions by the strong plasma turbulence model of pulsar radio emission. We also present other observed properties of the single pulses and discuss their relation to other single-pulse phenomena like giant pulses.

scholarly journals Search for a Correlation Between Radio Giant Pulses and VHE Photons of the Crab Pulsar

10.14311/1472 ◽  
2011 ◽  
Vol 51 (6) ◽  
Author(s):  
N. Lewandowska ◽  
D. Elsäesser ◽  
K. Mannheim
Keyword(s):  
Radio Emission ◽  
Special Form ◽  
Electromagnetic Spectrum ◽  
Crab Pulsar ◽  
Pulsar Emission ◽  
Pulsar Radio ◽  
Giant Pulses ◽  
Pulse Structure ◽  
Unique Source ◽  
Pulsar Radio Emission

The Crab pulsar is a unique source of pulsar radio emission. Its regular pulse structure is visible over the entire electromagnetic spectrum from radio to GeV ranges. Among the regular pulses, radio giant pulses (GPs) are known as a special form of pulsar radio emission. Although the Crab pulsar was discovered by its GPs, their origin and emission mechanisms are currently not understood. Within the framework of this report we give a review on radio GPs and present a new idea on how to examine the characteristics of this as yet not understood kind of pulsar emission.

scholarly journals Single Pulses and the Plasma-physical Processes of Pulsar Radio Emission

2017 ◽  
Vol 13 (S337) ◽  
pp. 73-78
Author(s):  
Joanna M. Rankin
Keyword(s):  
Radio Emission ◽  
Pulse Sequences ◽  
Single Pulse ◽  
Physical Processes ◽  
Pulsar Emission ◽  
Pulsar Radio ◽  
Cone Model ◽  
Chart Recorder ◽  
Polarization Characteristics ◽  
Pulsar Radio Emission

AbstractPulsars were discovered on the basis of their individual pulses, first by Jocelyn Bell and then by many others. This was chart-recorder science as computers were not yet in routine use. Single pulses carry direct information about the emission process as revealed in the detailed properties of their polarization characteristics. Early analyses of single pulses proved so dizzyingly complex that attention shifted to study of average profiles. This is turn led to models of pulsar emission beams—in particular the core/double-cone model—which now provides a foundation for understanding single-pulse sequences. We mention some of the 21stC single-pulse surveys and conclude with a brief discussion of our own recent analyses leading to the identification of the pulsar radio-emission mechanism of both slow and millsecond pulsars.

scholarly journals Characteristics of Pulsar Radio Emission at Single-pulse Resolution

2000 ◽  
Vol 177 ◽  
pp. 149-154
Author(s):  
Avinash A. Deshpande
Keyword(s):  
Radio Emission ◽  
Weighted Average ◽  
Single Pulse ◽  
Position Angle ◽  
Complex Nature ◽  
Stable States ◽  
Pulsar Radio ◽  
Emission Profile ◽  
Secondary State ◽  
Pulsar Radio Emission

Pulsar radio emission shows remarkably rich, but complex behavior in both intensity and polarization when considered on a pulse-to-pulse basis. A large number of pulses, when averaged together, tend to approach & define stable shapes that can be considered as distinct signatures of different pulsars. Such average profiles have shapes ranging from that describable as a simple one-component profile to those suggesting as many as 9 components. The components are understood as resulting from an average of many, often narrower, intities — the subpulses —that appear within the longitude range of a given component. The pulse components are thusformedand represent statistically an intensity-weighted average pattern of the radiation received as a function of longitude. The profile mode changes recognized in many pulsars suggest that the emission profile of a given pulsar may have two quasi-stable states, with one (primary) state more probable/brighter than the other (secondary) state. There are also (often associated) polarization modes that represent polarization states that are orthogonal to each other. The complex nature of orthogonaljumpsobserved in polarization position-angle sweeps may be attributable to possible superposition of two profile/polarization modes with orthogonal polarizations.

scholarly journals Pulsar radio beams and emission altitudes

1996 ◽  
Vol 160 ◽  
pp. 287-288
Author(s):  
Jaroslaw Kijak ◽  
Janusz A. Gil
Keyword(s):  
Emission Region ◽  
Intensity Level ◽  
Pulse Profile ◽  
Pulsar Emission ◽  
Pulsar Radio ◽  
Pulsar Radiation ◽  
Measured Profile ◽  
Field Lines ◽  
The Relationship ◽  
Pulsar Radio Emission

We verify the relationship proposed by Kijak and Gil (1996) for the pulsar radio emission altitudes(see also Eq.3 in Gil & Krawczyk, 1996), using the pulse-profile Effelsberg raw data at 1.41 GHz. We measured profile pulse-widths at the lowest intensity level corresponding to 0.01% of the maximum intensity (Fig. 1b), using the polarlog-scale technique (Hankins and Fowler, 1986). We calculated opening angles (Fig. 1a) and emission altitudes (Fig. 1c) assuming that:i) pulsar radiation is narrow-band with radius-to-frequency mapping operating in the emission region,ii) pulsar emission is beamed tangentially to the dipolar magnetic field lines,iii) the extreme profile wings originate near or at the last open field lines.

scholarly journals Single Pulse Analysis of the Core-Dominated Pulsar B0611+22

2000 ◽  
Vol 177 ◽  
pp. 175-176
Author(s):  
Jeffrey S. Kern
Keyword(s):  
Single Pulse ◽  
Emission Region ◽  
Surprising Result ◽  
Polar Cap ◽  
Pulsar Radio ◽  
The Core ◽  
Dependent Behavior ◽  
Region I ◽  
Pulse Analysis ◽  
Pulsar Radio Emission

AbstractSingle pulse studies of pulsar radio emission provide a window into the time dependent behavior of the radio loud region. I have analyzed a series of precision polarimetric observations of pulsar B0611+22 to determine the geometry of the emission region. The observations are consistent with a central core emission region, and a periodically present conal component. This identification leads to the surprising result that all emission is from the leading half of the polar cap.

scholarly journals Visibility of Pulsar Emission: Motion of the Visible Point

2014 ◽  
Vol 31 ◽  
Author(s):  
R. Yuen ◽  
D. B. Melrose
Keyword(s):  
Field Line ◽  
Vector Model ◽  
Line Of Sight ◽  
Dipolar Field ◽  
Pulsar Emission ◽  
Pulsar Radio ◽  
Wide Range ◽  
Recent Claim ◽  
Rotational Phase ◽  
Pulsar Radio Emission

AbstractA standard model for the visibility of pulsar radio emission is based on the assumption that the emission is confined to a narrow cone about the tangent to a dipolar field line. The widely accepted rotating vector model (RVM) is an approximation in which the line of sight is fixed and the field line is not strictly tangent to it. We refer to an exact treatment (Gangadhara, 2004) as the tangent model. In the tangent model (but not in the RVM) the visible point changes as a function of pulsar rotational phase, ψ, defining a trajectory on a sphere of radius r. We solve for the trajectory and for the angular velocity of the visible point around it. We note the recent claim that this motion is observable using interstellar holography (Pen et al., 2014). We estimate the error introduced by use of the RVM and find that it is significant for pulsars with emission over a wide range of ψ. The RVM tends to underestimate the range of ψ over which emission is visible. We suggest that the geometry alone strongly favors the visible pulsar radio being emitted at a heights more than ten percent of the light-cylinder distance, where our neglect of retardation effects becomes significant.

scholarly journals Radio spectra of millisecond pulsars

2017 ◽  
Vol 13 (S337) ◽  
pp. 358-359
Author(s):  
Vladislav Kondratiev ◽  
Anna Bilous ◽  
Keyword(s):  
Low Frequency ◽  
Flux Measurement ◽  
Power Laws ◽  
Published Data ◽  
Frequency Range ◽  
Pulsar Emission ◽  
Millisecond Pulsars ◽  
Pulsar Radio ◽  
Broadband Radio ◽  
Timing Data

AbstractBoth the physics of the pulsar emission mechanism and free-free absorption in the intervening interstellar medium can be tested with the pulsar radio spectra. We have built on our previous work on describing LOFAR population of millisecond pulsars (MSPs; Kondratiev et al. 2016) and HBA census of slow pulsars (Bilous et al. 2016) and present the study of radio spectra of the MSPs with a special attention on the low-frequency turnover. Using LOFAR timing data allowed us to measure flux densities of many MSPs over time span of up to three years in the frequency range 110–188 MHz. This provided more reliable estimates of mean flux densities and spectra reducing the influence of refractive scintillation, ionosphere and other factors on a single flux measurement. Together with published data at other radio frequencies we constructed pulsars’ spectra and fitted them with single or broken power-laws. We discuss the obtained spectra and their fits, paying special attention to the low-frequency turnover, and compare broadband radio spectra of MSPs to those of normal pulsars.

scholarly journals Pulsar Studies at High Radio Frequencies

2000 ◽  
Vol 177 ◽  
pp. 205-210 ◽  
Author(s):  
Richard Wielebinski
Keyword(s):  
Radio Sources ◽  
Radio Telescopes ◽  
Frequency Range ◽  
High Luminosity ◽  
Max Planck ◽  
Pulsar Emission ◽  
Millisecond Pulsars ◽  
Pulsar Radio ◽  
Radio Frequencies ◽  
Pulsar Radio Emission

AbstractPulsars were discovered at 81.5 MHz and a lot of the studies of these exciting objects have been made up to the present time at radio frequencies below 1.6 GHz. The reasons for this concentration on the low radio frequency characteristics of pulsars is the fact that the spectra are very steep and that very few radio telescopes exist that are capable of efficient operations at high radio frequencies. The Effelsberg 100-m radio telescope of the Max-Planck-Institut fur Radioastronomie operates regularly up to the frequency of 50 GHz and was used to study pulsars at cm/mm-wavelengths. In the southern skies the Parkes 64-m telescope has been used to study pulsars up to 8.4 GHz. One pulsar has been detected at 87 GHz with the 30-m Pico Veleta telescope of IRAM.The studies of pulsars over the whole frequency range are of great importance because this is necessary for the elucidation of the mechanism that is responsible for the pulsar emission. The high polarization of pulsar radio emission at lower radio frequencies has supported the hypothesis of a coherent emission mechanism, which is required to generate the high luminosity. It has been known for some time that pulsars, unlike other radio sources, have a lower polarization at high radio frequencies. Recently a change of pulsar spectrum, a flattening or possibly an inversion has been observed at the highest radio frequencies. The inversion of the pulsar spectrum seems to coincide with a complete depolarization of some pulsars.Millisecond pulsars are less luminous than normal pulsars. This makes them even more difficult to detect at higher radio frequencies. Recent observations have extended the spectra of ten millisecond pulsars up to 4.85 GHz. The results imply that millisecond pulsars have properties very similar to normal (slow) pulsars, which suggests similar emission mechanisms.

scholarly journals Polarization sounding of the pulsar magnetosphere

2012 ◽  
Vol 8 (S291) ◽  
pp. 530-532 ◽  
Author(s):  
O. M. Ulyanov ◽  
A. I. Shevtsova ◽  
A. A. Seredkina
Keyword(s):  
Broad Band ◽  
Probe Signal ◽  
Pulsar Magnetosphere ◽  
Free Electrons ◽  
Pulsar Emission ◽  
Pulsar Radio ◽  
Decameter Wavelength ◽  
Propagation Medium ◽  
Pulsar Radio Emission ◽  
Stratified Model

AbstractThe possibility of a polarization sounding of the pulsar magnetosphere is examined, using intrinsic pulsar emission as a probe signal, for modern radio telescopes operating in the meter and decameter wavelength range. Different models of the pulsar magnetosphere at altitudes higher than a radius of critical polarization are used. The propagation medium besides magnetosphere is described by the stratified model, in which each layer has its own density of free electrons and vector of magnetic induction, as well as the spatial and temporal fluctuation scales of these parameters.The frequency dependence of the polarization parameters of the pulsar radio emission, obtained in the broad band for a selected pulse phase, will enable a sounding deep into the pulsar magnetosphere.

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