scholarly journals Annular gap model for multi-wavelength pulsed emission from young and millisecond pulsars

2012 ◽  
Vol 8 (S291) ◽  
pp. 378-380
Author(s):  
Yuan Jie Du ◽  
Guo Jun Qiao
Keyword(s):  
Inclination Angle ◽  
Pole Model ◽  
Viewing Angle ◽  
Gap Model ◽  
Magnetic Pole ◽  
Millisecond Pulsars ◽  
Annular Gap ◽  
Magnetic Inclination ◽  
Multi Wavelength

AbstractThe multi-wavelength pulsed emission from young pulsars and millisecond pulsars can be well modeled with the single-pole 3-dimension annular gap and core gap model. To distinguish our single magnetic pole model from two-pole models (e.g. outer gap model and two-pole caustic model), the convincing values of the magnetic inclination angle and the viewing angle will play a key role.

scholarly journals The annular gap model for γ-ray emission from young and millisecond pulsars

2010 ◽  
Vol 406 (4) ◽  
pp. 2671-2677 ◽  
Author(s):  
Y. J. Du ◽  
G. J. Qiao ◽  
J. L. Han ◽  
K. J. Lee ◽  
R. X. Xu
Keyword(s):  
Gap Model ◽  
Millisecond Pulsars ◽  
Annular Gap ◽  
Γ Ray

scholarly journals A Determination of Pulsar Emission Geometry from Polarization Observations

1992 ◽  
Vol 128 ◽  
pp. 400-403
Author(s):  
Xinji Wu ◽  
Wen Xu
Keyword(s):  
Inclination Angle ◽  
Pulse Width ◽  
Rotation Axis ◽  
Geometrical Model ◽  
Polarization Angle ◽  
Radiation Beam ◽  
Pulsar Emission ◽  
Magnetic Inclination ◽  
Large Pulse

AbstractOne of the important problems in pulsar studies is to determine the magnetic inclination angle α, the intrinsic width of the radiation beam (2ρ) and the angle (α + β) between the observer's direction and the rotation axis. In this paper we solve this problem for individual pulses by using the observed pulse width (2Δ𝜙), the swing of polarization angle (2Δψ), and its central gradient (dψ/d𝜙)max.From the polar cap model we establish three basic geometrical relations, a complete set of equations from which explicit solutions can be obtained using the observed data. This is the first time that the orientation of pulsar emission is solved analytically solely on the basis of a geometrical model. However, the results are shown to be sensitively connected to the polarization-angle swing (2Δψ), which is not well measured for most pulsars. So the number of pulsars to which our method can be applied is limited. The importance of the measurement of Δψ is seen from our method. To ensure the credibility of our results, we have discussed the conditions to be satisfied by all reliable pulsar measurements. Our method is shown to be more favorable for pulsars with large pulse width 2Δ𝜙, large central gradient (dψ/d𝜙)max and large magnetic inclination angle α. Out of 120 pulsars (from Lyne and Manchester 1988), 40 are solvable, and 7 are believed to be reliable. We discuss our method for the determination of pulsar geometry in comparison with other methods.

scholarly journals Gamma-ray emission in radio galaxies under the VLBI scope

2019 ◽  
Vol 627 ◽  
pp. A148 ◽  
Author(s):  
R. Angioni ◽  
E. Ros ◽  
M. Kadler ◽  
R. Ojha ◽  
C. Müller ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Monitoring Program ◽  
Radio Galaxies ◽  
High Energy ◽  
Viewing Angle ◽  
Long Baseline ◽  
Superluminal Motion ◽  
Multi Wavelength ◽  
The Individual ◽  
The Relationship

Aims. In the framework of the multi-wavelength and very long baseline interferometry (VLBI) monitoring program TANAMI (Tracking Active Nuclei with Austral Milliarcsecond Interferometry), we study the evolution of the parsec-scale radio emission in radio galaxies in the southern hemisphere and their relationship to the γ-ray properties of the sources. Our study investigates systematically, for the first time, the relationship between the two energy regimes in radio galaxies. In this first paper, we focus on Fermi-LAT-detected sources. Methods. The TANAMI program monitors a large sample of radio-loud AGN at 8.4 GHz and 22.3 GHz with the Australian long baseline array (LBA) and associated telescopes in Antarctica, Chile, New Zealand and South Africa. We performed a kinematic analysis for five γ-ray detected radio galaxies using multi-epoch 8.4 GHz VLBI images, deriving limits on intrinsic jet parameters such as speed and viewing angle. We analyzed 103 months of Fermi-LAT data in order to study possible connections between the γ-ray properties and the pc-scale jets of Fermi-LAT-detected radio galaxies, both in terms of variability and average properties. We discuss the individual source results and draw preliminary conclusions on sample properties including published VLBI results from the MOJAVE (Monitoring Of Jets in Active galactic nuclei with VLBA Experiments) survey, with a total of fifteen sources. Results. We find that the first γ-ray detection of Pictor A might be associated with the passage of a new VLBI component through the radio core, which appears to be a defining feature of high-energy emitting Fanaroff-Riley type II radio galaxies. We detect subluminal parsec-scale jet motions in the peculiar AGN PKS 0521−36, and we confirm the presence of fast γ-ray variability in the source down to timescales of six hours, which is not accompanied by variations in the VLBI jet. We robustly confirm the presence of significant superluminal motion, up to βapp ∼ 3, in the jet of the TeV radio galaxy PKS 0625−35. Our VLBI results constrain the jet viewing angle to be θ <  53°, allowing for the possibility of a closely aligned jet. Finally, by analyzing the first pc-scale multi-epoch images of the prototypical compact symmetric object (CSO) PKS 1718−649, we place an upper limit on the separation speed between the two mini-lobes. This in turn allows us to derive a lower limit on the age of the source. Conclusions. We can draw some preliminary conclusions on the relationship between pc-scale jets and γ-ray emission in radio galaxies, based on Fermi-LAT-detected sources with available multi-epoch VLBI measurements. We find that the VLBI core flux density correlates with the γ-ray flux, as seen in blazars. On the other hand, the γ-ray luminosity does not show any dependence on the core brightness temperature and core dominance, which are two common indicators of jet Doppler boosting. This seems to indicate that γ-ray emission in radio galaxies is not driven by orientation-dependent effects, as in blazars, in accordance with the unified model of jetted AGN.

scholarly journals A decade of transitional millisecond pulsars

2017 ◽  
Vol 13 (S337) ◽  
pp. 47-51 ◽  
Author(s):  
Amruta Jaodand ◽  
Jason W. T. Hessels ◽  
Anne Archibald
Keyword(s):  
Neutron Stars ◽  
Millisecond Pulsar ◽  
Physical Processes ◽  
Recycling Process ◽  
Millisecond Pulsars ◽  
X Ray ◽  
System A ◽  
Multi Wavelength ◽  
Low Mass

AbstractTransitional millisecond pulsars (tMSPs), which are systems that harbor a pulsar in the throes of the recycling process, have emerged as a new source class since the discovery of the first such system a decade ago. These systems switch between accretion-powered low-mass X-ray binary (LMXB) and rotation-powered radio millisecond pulsar (RMSP) states, and provide exciting avenues to understand the physical processes that spin-up neutron stars to millisecond periods. During the last decade, three tMSPs, as well as a candidate source, have been extensively probed using systematic, multi-wavelength campaigns. Here we review the observational highlights from these campaigns and our general understanding of tMSPs.

scholarly journals Results of Theoretical Definition of Structural and Kinematic Parameters of Peeling Machine Working Elements

2020 ◽  
Vol 30 (4) ◽  
pp. 594-608
Author(s):  
Alexander V. Anisimov ◽  
Feliks Ya. Rudik
Keyword(s):  
Angular Velocity ◽  
Inclination Angle ◽  
Material Point ◽  
Machine Design ◽  
Cylinder Surface ◽  
Kinematic Parameters ◽  
Energy Assessment ◽  
Annular Gap ◽  
Working Bodies ◽  
Definition Of

Introduction. Peeling the moistened grains before grinding allows removing most of the outer shells with impurities on them from the grain surface. At the present time, the most commonly used machines for peeling are devices operating on the principle of “compression and friction”, in which the grains move along the friction surfaces of the working bodies. The aim of this study is to define and select structural and kinematic parameters of the machine working bodies, which would most effectively perform the process of peeling, and to make energy assessment of grain peeling. Materials and Methods. To identify the dependence of the machine design and operating parameters on the inclination angle and punching angle of the sieve cylinder, a diagram of the movement of the grain along the inclined cylinder was drawn up using elements of the theory of the motion of material point on rough surfaces. The motion of grains on the cylinder surface is analyzed by the methods of analytical dynamics. Results. The values of the geometric parameters of the particle position at point A are expressed as a function of the cylinder inclination angle α and the angle characterizing the shape of the inclined line of stamping of the cylinder β. Energy assessment of grain peeling process was made. With the radius of the sieve cylinder R0 = 0.135 m, the width of the working annular gap к = 0.01 m, the length of the cylinder L = 0.4 m, the horizontal arrangement of the cylinder, the angular velocity of the shaft ω = 90 rad/s, the angle of inclination of the stamping β = 22º, the calculated power was P = 4.5 kW. Discussion and Conclusion. As a result of analyzing the motion trajectory of the grain located on the cylinder surface, there have been proposed the formulas relating the shape of the inclined punching line of the cylinder, characterized by the angle β, to the inclination angle α, the radius R0 of the cylinder, the shaft angular velocity and the grain frictional properties. The obtained analytical dependencies can be used for the approximate definition of the peeling machine design and kinematic parameters.

scholarly journals DETECTION OF MAGNETIC INCLINATION ANGLE BY SEA TURTLES: A POSSIBLE MECHANISM FOR DETERMINING LATITUDE

1994 ◽  
Vol 194 (1) ◽  
pp. 23-32 ◽  
Author(s):  
K Lohmann ◽  
C Lohmann
Keyword(s):  
Inclination Angle ◽  
Sea Turtles ◽  
Positional Information ◽  
Compass Orientation ◽  
Loggerhead Sea Turtles ◽  
Southern Boundary ◽  
The North ◽  
Magnetic Inclination ◽  
Inclination Angles ◽  
Field Lines

For animals that migrate long distances, the magnetic field of the earth provides not only a possible cue for compass orientation, but a potential source of world-wide positional information. At each location on the globe, the geomagnetic field lines intersect the earth's surface at a specific angle of inclination. Because inclination angles vary with latitude, an animal able to distinguish between different field inclinations might, in principle, determine its approximate latitude. Such an ability, however, has never been demonstrated in any animal. We studied the magnetic orientation behavior of hatchling loggerhead sea turtles (Caretta caretta L.) exposed to earth-strength magnetic fields of different inclinations. Hatchlings exposed to the natural field of their natal beach swam eastward, as they normally do during their offshore migration. In contrast, those subjected to an inclination angle found on the northern boundary of the North Atlantic gyre (their presumed migratory path) swam south-southwest. Hatchlings exposed to an inclination angle found near the southern boundary of the gyre swam in a northeasterly direction, and those exposed to inclination angles they do not normally encounter, or to a field inclination found well within the northern and southern extremes of the gyre, were not significantly oriented. These results demonstrate that sea turtles can distinguish between different magnetic inclination angles and perhaps derive from them an approximation of latitude. Most sea turtles nest on coastlines that are aligned approximately north&shy;south, so that each region of nesting beach has a unique inclination angle associated with it. We therefore hypothesize that the ability to recognize specific inclination angles may largely explain how adult sea turtles can identify their natal beaches after years at sea.

The Magnetic Pole Model for Pulsar Emission

1978 ◽  
Vol 3 (3) ◽  
pp. 200-205 ◽  
Author(s):  
R. N. Manchester
Keyword(s):  
Duty Cycle ◽  
Pulse Train ◽  
Pole Model ◽  
Magnetic Pole ◽  
Pulse Profile ◽  
Pulsar Emission ◽  
Periodic Pulse ◽  
The Mean

Pulsars are unique astronomical objects in that their emission is in the form of a periodic pulse train. For most pulsars the pulse duty cycle is small, only a few per cent of the period. The shapes and intensities of individual pulses are in general quite variable. This is illustrated in Figure 1 which shows a series of individual pulses from PSR 1133 + 16. Despite this variation in shape of individual pulses, it is found that the mean or integrated pulse profile obtained by adding many pulses synchronously with the period is in most cases stable in shape.

Elliptically Polarized Natural Modes in Pulsar Magnetospheres

1982 ◽  
Vol 4 (4) ◽  
pp. 365-370 ◽  
Author(s):  
Michelle C. Allen ◽  
D.B. Melrose
Keyword(s):  
Circular Polarization ◽  
Linear Polarization ◽  
Strong Support ◽  
Position Angle ◽  
Average Degree ◽  
Pole Model ◽  
Magnetic Pole ◽  
Pulse Profile ◽  
Linearly Polarized ◽  
High Degree

The most obvious feature of the polarization of the radio emission from most pulsars is the rotation of the plane of linear polarization across pulses. The original interpretation of this in terms of the magnetic pole model (Radhakrishnan 1969, Radhakrishnan et al. 1969, Radhakrishnan and Cooke 1969) accounts for the variation of position angle extremely well for some pulsars (e.g. Manchester and Taylor 1977, Manchester 1978). Conversely, this provides strong support for the magnetic pole model for pulsar emission. It also suggests that the emission is basically linearly polarized as implied by virtually all proposed emission mechanisms, e.g. the reviews by Ginzburg and Zheleznyakov (1975) and Arons (1979). However, there are two features of the polarization which require a separate explanation. First, some pulsars have a moderately high degree of circular polarization, even in the integrated pulse profile (Manchester 1971, Lyne, Smith and Graham 1971). In some pulsars the average degree of circular polarization can exceed the average degree of linear polarization, e.g. in PSR 0835-41 and 0959-54 (McCulloch et al. 1978). Second, some pulsars exhibit the phenomenon of transitions between orthogonal elliptical polarizations (Manchester, Taylor and Huguenin 1975, Backer, Rankin and Campbell 1976, Cordes and Hankins 1977, Cordes, Rankin and Backer 1978). In many pulsars the orthogonal polarizations have substantial circular components, e.g. in PSR 1133 + 16 (Manchester et al. 1975) and PSR 2020 + 28 (Cordes et al. 1978).

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