scholarly journals Profile Changes in the Binary Pulsar PSR 1913+16

1992 ◽  
Vol 128 ◽  
pp. 214-216
Author(s):  
J. M. Weisberg ◽  
J. H. Taylor

AbstractAccording to general relativity, the spin axis of binary pulsar PSR 1913+16 should precess at a rate of 1.21 degrees per year. This precession will cause the pulse profile to change as our line of sight samples different pulsar latitudes. In order to search for this phenomenon, we have carefully monitored the pulse profile at 1408 MHz for 8.5 years. The ratio of flux density of the first to second pulse component has declined at a rate of approximately 1.65% per year, with some evidence of a steeper decrease over the past three years. We have detected no evidence for a change in the separation of the two components. We discuss the nature of the pulsar emission region in light of these results.

2000 ◽  
Vol 177 ◽  
pp. 127-130 ◽  
Author(s):  
Joel M. Weisberg ◽  
Joseph H. Taylor

AbstractRelativistic spin-orbit coupling should cause the spin axis of Binary Pulsar B1913+16 to precess at a rate of about 1 deg / yr. As a result, the pulse profile is expected to exhibit secular evolution. Weisberg, Romani, & Taylor (1989), and Weisberg & Taylor (1992) found that the intensity ratio of the two conal components changed at a one percent per year rate from 1981 to 1989, but that their spacing did not measurably change. They attributed these observations to our line of sight passing across the middle of a patchy cone of emission. Recently Kramer (1998) found that the intensity ratio continued its secular change for another decade, and also detected a narrowing of the conal component separation.We present our analysis of eighteen years of 21 cm pulse profile data. We confirm that the profile is narrowing as precession finally carries our line of sight away from the emission beam axis, and we map the beam in two dimensions. The beam is elongated in the latitude direction, and the degree of elongation grows with radius.


2019 ◽  
Vol 489 (1) ◽  
pp. 310-324 ◽  
Author(s):  
Lucy Oswald ◽  
Aris Karastergiou ◽  
Simon Johnston

ABSTRACT The frequency widening of pulsar profiles is commonly attributed to lower frequencies being produced at greater heights above the surface of the pulsar; so-called radius-to-frequency mapping (RFM). The observer’s view of pulsar emission is a 1D cut through a 3D magnetosphere: we can only see that emission which points along our line of sight. However, by comparing the frequency evolution of many single pulses positioned at different phases, we can build up an understanding of the shape of the active emission region. We use single pulses observed with the Giant Metrewave Radio Telescope to investigate the emission region of PSR J1136+1551 and test RFM. Assuming that emission is produced tangential to the magnetic field lines and that each emission frequency corresponds to a single height, we simulate the single pulse profile evolution resulting from the canonical conal beam model and a fan beam model. Comparing the results of these simulations with the observations, we conclude that the emission region of PSR J1136+1551 is better described by the fan beam model. The diversity of profile widening behaviour observed for the single pulses can be explained by orthogonally polarized modes propagating along differing frequency-dependent paths in the magnetosphere.


1996 ◽  
Vol 160 ◽  
pp. 287-288
Author(s):  
Jaroslaw Kijak ◽  
Janusz A. Gil

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.


2001 ◽  
Vol 205 ◽  
pp. 408-409
Author(s):  
I.H. Stairs ◽  
S.E. Thorsett ◽  
J.H. Taylor ◽  
Z. Arzoumanian

We present the results of recent Arecibo observations of the relativistic double-neutron-star binary PSR B1534+12. The timing solution includes measurements of five post-Keplerian orbital parameters, whose values agree well with the predictions of general relativity. The observations show that the pulse profile is evolving secularly at both 1400 MHz and 430 MHz. This effect is similar to that seen in PSR B1913+16, and is almost certainly due to general relativistic precession of the pulsar's spin axis. We also present high-quality polarimetric profiles at both observing frequencies.


2020 ◽  
Vol 639 ◽  
pp. A75
Author(s):  
Q. Giraud ◽  
J. Pétri

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.


1992 ◽  
Vol 128 ◽  
pp. 225-227
Author(s):  
R. C. Kapoor

AbstractAn estimate of the effect of light bending and redshift on pulsar beam characteristics has been made using a weak Kerr metric for the case of a 1.4 M⊙ neutron star with a radius in the range 6-10 km and rotation periods of 1.56 ms and 33 ms, respectively. Assuming that the pulsar emission has the form of a narrow conical beam directed away from the surface and is located within two stellar radii, the beam is found to be widened by a factor of ≤ 2 and to suffer a reduction in the intensity (flattening of the profile) by an order of magnitude or less. The effect is largest for the most rapidly rotating the neutron stars. For an emission region located beyond 20 km, the flattening is generally insignificant. The pulse profile is slightly asymmetrical due to dragging of the inertial frames. For millisecond periods, aberration tends to reverse the flattening effect of space-time curvature by narrowing the pulse and can completely overcome it for emission from a location beyond ≃30km. Although the pulse must slightly brighten up, a large redshift factor overcomes this effect to keep the pulse flattened for all neutron star radii considered here.


1991 ◽  
Vol 148 ◽  
pp. 15-23 ◽  
Author(s):  
B. E. Westerlund

A vast amount of observational data concerning the structure and kinematics of the Magellanic Clouds is now available. Many basic quantities (e.g. distances and geometry) are, however, not yet sufficiently well determined. Interactions between the Small Magellanic Cloud (SMC), the Large Magellanic Cloud (LMC) and our Galaxy have dominated the evolution of the Clouds, causing bursts of star formation which, together with stochastic self-propagating star formation, produced the observed structures. In the youngest generation in the LMC it is seen as an intricate pattern imitating a fragmented spiral structure. In the SMC much of the fragmentation is along the line of sight complicating the reconstruction of its history. The violent events in the past are also recognizable in complex velocity patterns which make the analysis of the kinematics of the Clouds difficult.


2020 ◽  
Vol 642 ◽  
pp. L4
Author(s):  
Dana A. Kovaleva ◽  
Marina Ishchenko ◽  
Ekaterina Postnikova ◽  
Peter Berczik ◽  
Anatoly E. Piskunov ◽  
...  

Context. Given the closeness of the two open clusters Collinder 135 and UBC 7 on the sky, we investigate the possibility that the two clusters are physically related. Aims. We aim to recover the present-day stellar membership in the open clusters Cr 135 and UBC 7 (300 pc from the Sun) in order to constrain their kinematic parameters, ages, and masses and to restore their primordial phase space configuration. Methods. The most reliable cluster members are selected with our traditional method modified for the use of Gaia DR2 data. Numerical simulations use the integration of cluster trajectories backwards in time with our original high-order Hermite4 code φ−GRAPE. Results. We constrain the age, spatial coordinates, velocities, radii, and masses of the clusters. We estimate the actual separation of the cluster centres equal to 24 pc. The orbital integration shows that the clusters were much closer in the past if their current line-of-sight velocities are very similar and the total mass is more than seven times larger than the mass of the most reliable members. Conclusions. We conclude that the two clusters Cr 135 and UBC 7 might very well have formed a physical pair based on the observational evidence as well as numerical simulations. The probability of a chance coincidence is only about 2%.


2021 ◽  
Vol 19 (4) ◽  
pp. 01-14
Author(s):  
Meriama Hansali Mebarki

The reinforcement sensitivity theory lacks basic sources of any human experience :time, place, and learning contexts that have shaped the reinforcement; therefore I have assumed a missing link in Gray's framework based on special relativity relying on the «what, where, and when of happenning»? as major resources of human conscious experience, which under punishment or reward exceed the sensitivity to pleasant or unpleasant stimuli transcending therefore the Weber law, that's why I called it: Psychological Space-Time Reinforcement Sensitivity “PSTRS” axis. The lasts explains BAS and BIS systems sensitivity to reinforcement across the cognitive space-time continuum of episodic memory, and not only across the two great dimensions of fear/anxiety and defensive distance of the McNaughton & Corr model of 2004. So, based on the disruption of the high-sensitivity information processing system in the brain, the four-dimensional conscious experience is distorted by its underlying sources and context. Thus, one of the timedominating records prevents the individual from overcoming the present., such in depression, obsessive compulsive disorder and post-traumatic stress disorder (psychological sensitivity to the past). These temporal records clearly lose their sequence and associative nature in dissociative symptoms due to the disruption of the most important milestone on which Einstein's physics was based. Consequently, psychological space-time reinforcement sensitivity supposes that psychological disorders can be interpreted according to the laws of special relativity (acceleration / deceleration), but this seems more complicated when it comes to mental disorders where the self is disturbed on its spatio-temporal axis as observed in schizophrenia. Schizophrenia looks like a three-componements disorder characterized by a disruption of the experience of time, place and self, which could be asummed up as a “self space-time disturbance". Notably schizophrenic patients appear losing the ability to gather in a dynamic way these componements, as if the world seemed missig the gestalt characteristic or fragmented. The past felt like an inevitable destiny inhibits the direction towards the future; sometimes disorient the self to the point of feeling lost, as if the psychological time slows down to the point of feeling separated from the « now » the physical time. So are we dealing with an Euclidian space? The article attempts to provide a non-traditional interpretation of mental disorders by including general relativity in psychological studies, based on the neurobiological bases involved in the spatio-temporal processing of the conscious experience in the quantum brain.


1969 ◽  
Vol 1 (5) ◽  
pp. 233-234
Author(s):  
H. S. Murdoch

The over-estimation of the flux density of radio sources near the lower limit of a survey has often been considered in the past. The use of digital recording and analysis techniques now enables a quantitative approach to the problem. Monte Carlo techniques may be used to determine the error distribution, including any systematic bias.


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