scholarly journals Multifrequency Study of Periodic Nulling and Subpulse Drifting in Pulsar J2048−1616

2021 ◽  
Vol 923 (2) ◽  
pp. 259
Author(s):  
Z. Wang ◽  
Z. G. Wen ◽  
J. P. Yuan ◽  
N. Wang ◽  
J. L. Chen ◽  
...  
Keyword(s):  
Spectral Analysis ◽  
Radio Telescope ◽  
Pulse Sequences ◽  
Single Pulse ◽  
Central Core ◽  
Central Component ◽  
Pulse Emission ◽  
Physical Mechanisms ◽  
The Core ◽  
Fluctuation Rate

Abstract We have carried out a detailed study of single-pulse emission from the pulsar J2048−1616 (B2045−16), observed at 732, 1369, and 3100 MHz frequencies using the Parkes 64 m radio telescope. The pulsar possesses three well-resolved emission components, with the central component resembling core emission. The single pulses show the presence of two distinct periodic modulations using fluctuation spectral analysis. About 12% nulls are found to create alternating bunches of nulls and bursts in a quasiperiodic manner with longer periodicities of 83, 28, and 14 rotational periods for simultaneous observations at 732 and 3100 MHz. At 1369 MHz, the quasiperiodic nulling is detected, as well, to modulate across the entire profile both in the core and conal components simultaneously with a fluctuation rate of about 50 rotational periods, and the nulling fraction is estimated to be around 10%. Additionally, the quasiperiodic modulations are significantly dependent on time. In addition to nulling, the pulsar also presents subpulse drifting in the single-pulse sequences with shorter periodicity. The subpulse drifting is presented in the conal components and is absent in the central core emission. The leading component is modulated in longitude with a period of three pulses. The trailing component remains phase stationary within the pulse window but periodically modulates in amplitude with a period of three pulses. Finally, possible physical mechanisms are discussed.

scholarly journals Arecibo 4.5/1.4/0.33-GHz polarimetric single-pulse emission survey

2019 ◽  
Vol 489 (2) ◽  
pp. 1543-1555 ◽  
Author(s):  
Timothy E E Olszanski ◽  
Dipanjan Mitra ◽  
Joanna M Rankin
Keyword(s):  
Linear Polarization ◽  
High Frequency ◽  
Pulse Sequences ◽  
Single Pulse ◽  
Beam Model ◽  
High Quality ◽  
Pulse Emission ◽  
The Core ◽  
Emission Beam ◽  
Almost All

ABSTRACT We report on an Arecibo 4.5-GHz polarimetric single-pulse survey of the brightest pulsars at high frequency within its sky. The high-frequency profiles are accompanied by a collection of both previously published and unpublished high quality 1.4- and 0.33-GHz observations. Here our analyses and discussion primarily involve the average and statistical properties of the 46 pulsars polarimetric pulse sequences, profile classification and frequency evolution, and polarimetric profiles and peak-occurrence histograms. In most cases both the fractional linear polarization and profile widths decrease with frequency as expected, but there are some exceptions. Similarly, we were able to review and/or extend the profile classifications for this population of pulsars and work out their beaming characteristics quantitatively showing that almost all show properties compatible with the core/double-cone emission beam model. The entirety of these observations’ average profiles are accessible for download.

scholarly journals A Spectral Analysis of the Central Component of CTB 80

2004 ◽  
Vol 218 ◽  
pp. 211-212
Author(s):  
G. Castelletti ◽  
G. Dubner ◽  
K. Golap ◽  
W. M. Goss
Keyword(s):  
Spectral Analysis ◽  
Radio Telescope ◽  
Supernova Remnant ◽  
Central Component ◽  
Spectral Behavior

Based on observations of the extended supernova remnant CTB 80 carried out with the Giant Metrewave Radio Telescope (GMRT, India) at 240 and 618 MHz we have analyzed the spectral behavior of the ∼ 10′ nebula formed near the pulsar PSR B1951+32, finding signatures of the interaction of the pulsar with the surrounding plasma.

scholarly journals Subpulse drifting and periodic nulling in single pulse emission of PSR B2000+40

2020 ◽  
Vol 499 (1) ◽  
pp. 906-913 ◽  
Author(s):  
Rahul Basu ◽  
Wojciech Lewandowski ◽  
Jarosław Kijak
Keyword(s):  
Pulse Sequence ◽  
Single Pulse ◽  
Central Component ◽  
Core Component ◽  
Pulse Emission ◽  
Select Group ◽  
Large Phase ◽  
Pulse Behaviour ◽  
Phase Variations ◽  
Evolution With Time

ABSTRACT We have carried out a detailed study of single pulse emission from the pulsar B2000+40 (J2002+4050), observed at 1.6-GHz frequencies using the Effelsberg radio telescope. The pulsar has three components, which are not well separated, with the central component resembling core emission. We have investigated modulations in single pulse behaviour using the fluctuation spectral analysis, which showed the presence of two prominent periodicities, around 2.5P and 40P, respectively. The shorter periodicity was associated with the phenomenon of subpulse drifting and was seen to be absent in the central core component. Drifting showed large phase variations in conal components. Additionally, the periodic modulations had significant evolution with time, varying between very sharp and highly diffuse features. In addition to drifting the pulsar also had the presence of nulling in the single pulse sequence. The longer periodic feature in the fluctuation spectra was associated with nulling behaviour. The pulsar joins a select group, which shows the presence of the phase-modulated drifting as well as periodic nulling in the presence of core emission. This provides further evidence for the two phenomena to be distinct from each other with different physical origins.

scholarly journals Pulse Properties of a few Southern Pulsars at 150 MHz

2000 ◽  
Vol 177 ◽  
pp. 171-172
Author(s):  
Nalini H. Issur ◽  
Avinash A. Deshpande
Keyword(s):  
Radio Telescope ◽  
Pulse Sequences ◽  
Single Pulse ◽  
Millisecond Pulsar ◽  
Preliminary Results

AbstractWe present 150 MHz observations of the bright millisecond pulsar J0437-4715, and pulsars J1453-6413 and J1752-2806, made with the Mauritius Radio Telescope (MRT). We use single-pulse sequences to derive some preliminary results on the pulse morphologies.

The density variation of the earth's central core*

1942 ◽  
Vol 32 (1) ◽  
pp. 19-29
Author(s):  
K. E. Bullen
Keyword(s):  
Pure Iron ◽  
Outer Boundary ◽  
Density Variation ◽  
Central Core ◽  
Good Precision ◽  
Wide Margin ◽  
The Core ◽  
The Earth ◽  
The Mean ◽  
Published Paper

ABSTRACT A detailed analysis of the problem of the earth's density variation has been extended to the earth's central core. It is shown that in the region between the outer boundary of the core and a distance of about 1400 km. from the earth's center the density ranges from 9.4 gm/cm.3 to 11.5 gm/cm.3 within an uncertainty which, if certain general assumptions are true, does not exceed 3 per cent. The density and pressure figures are, moreover, compatible with the existence of fairly pure iron in this part of the earth. The result for the earth's outer mantle as given in a previously published paper, together with those in the present paper, are found to give with good precision the density distribution in a region occupying 99 per cent of the earth's volume. Values of the density within 1400 km. of the earth's center are subject, however, to a wide margin of uncertainty, and there appears to be no means of resolving this uncertainty for the present. The most that can be said is that the mean density in the latter region is greater than 12.3 gm/cm.3 and may quite possibly be several gm/cm.3 in excess of this figure. In the present paper figures are also included for the variation of gravity and the distribution of pressure within the central core. The gravity results are shown to be subject to an appreciable uncertainty except within about 1000 km. of the outer boundary of the core, but the pressure results are expected to be closely accurate at all depths.

Ultrastructure of the organ of Bellonci in the hypogean isopod Stenasellus virei boui Magniez (Crustacea, Asellota)

1992 ◽  
Vol 70 (1) ◽  
pp. 129-135
Author(s):  
Adriana Pitzalis ◽  
Christian Juberthie
Keyword(s):  
Glial Cells ◽  
Basal Body ◽  
Spatial Arrangement ◽  
Central Core ◽  
Sensory Cells ◽  
The Core ◽  
Ultrastructural Morphology

The ultrastructure of the organ of Bellonci in the hypogean isopod Stenasellus virei boui was investigated. There are two organs located anterodorsally, one on each side of the cephalon. Each organ consists of a wall surrounding a cavity with a central core irregular in shape. The bordering wall contains some glial cells and the inner dendritic segments of 25–28 sensory cells, each one bearing two cilia. Each cilium has a typical 9 + 0 axoneme, a basal body, and a long straight ciliary root that is at a right angle to the basal body; the cilium branches out into tubules that usually contain 1 microtubule, occasionally 2 or more. The ciliary tubules are gathered in three or four long bundles and are not linked to the core. The ciliary connections appear to be both conical and cylindrical. The ultrastructural morphology (polarization of the cilia, spatial arrangement of the bundles and central core) suggests that this organ can record directional stimuli.

scholarly journals Magnetic Study of the Heated and Unheated Sedimentary Fillings of Sebkha Mhabeul, Southeast Tunisia: A Geophysical Method for Paleoclimatic Investigation and Tephrochronological Dating

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Elhoucine Essefi ◽  
Samir Mefteh ◽  
Mounir Medhioub ◽  
Chokri Yaich
Keyword(s):  
Magnetic Susceptibility ◽  
Spectral Analysis ◽  
Little Ice Age ◽  
Complete Loss ◽  
The Other ◽  
Ice Age ◽  
Geophysical Method ◽  
Climate Anomalies ◽  
The Core ◽  
Southeast Tunisia

This paper is meant to investigate the climatic and volcanic signals within the sedimentary filling of sebkha Mhabeul through a thermomagnetic study of a 37 cm length core. Values of the magnetic susceptibility at ambient temperature show that the core encompasses four climatic stages: the Warming Present (WP), the Little Ice Age (Late LIA), Early Little Ice Age (ELIA), and the Medieval Climate Anomalies (MCA). Added to the subcycles, the spectral analysis shows the individualization of an 888 yr cycle probably related to solar activity. The heating at 250°C is good-for-nothing since it was useful neither for climatic investigation nor for tephras layers detection. Heating at 700°C generated the complete loss of the climatic signal. On the other hand, it allowed the detection of the previously identified tephras layers. Further, it highlighted the presence of other tephras layers. The extraction by the bromoform confirms the presence of these tephras. The use of the same methodology may allow the detection of tephras layers within other sebkhas.

Paleoeskimo Occupations of Central and High Arctic Canada

1976 ◽  
Vol 31 ◽  
pp. 15-39 ◽  
Author(s):  
Robert McGhee
Keyword(s):  
Temporal Distribution ◽  
High Arctic ◽  
Central Core ◽  
Hudson Bay ◽  
Arctic Canada ◽  
The Core ◽  
The Past ◽  
Archaeological Collections ◽  
Distribution Of Components ◽  
Cultural Discontinuities

Most of our knowledge regarding the Paleoeskimos of Arctic Canada is derived from the “core area” of Paleoeskimo occupation, a rough circle of some 1,000 km diameter including the coasts of Fury and Hecla Strait, Hudson Bay, and Hudson Strait. This is the area in which Dorset culture was first recognized, the source of most of our larger collections, and the area where continuity of development throughout the Paleoeskimo sequence has been demonstrated (Meldgaard 1962; Taylor 1968a; Maxwell 1973). The number and size of archaeological collections from this area suggest that it supported a larger Paleoeskimo population than did other regions of Arctic Canada, while the temporal distribution of components and continuities of style suggests that the region was occupied continuously throughout the Paleoeskimo period.In the fringe areas surrounding this central core, continuous occupation has not yet been demonstrated through any major segment of the Paleoeskimo sequence. Work in these fringe areas has rapidly progressed during the past decade, and it now seems certain that most of the temporal gaps and cultural discontinuities are not the result of poor archaeological sampling but reflect a situation of sporadic occupation occurring at different times in different regions. One of the striking features of the Paleoeskimo population was its propensity for expanding and retracting its geographical range, and this is the phenomenon which this paper will attempt to document. The primary aim of the paper is to sort out who lived where and when; a secondary aim is to suggest how they may have got there and what happened to them.

scholarly journals PAFINDER – Searching for FRBs and pulsars using Phased Array Feeds

2017 ◽  
Vol 13 (S337) ◽  
pp. 370-371
Author(s):  
Mateusz Malenta ◽  
Ewan Barr ◽  
Aaron Chippendale ◽  
Xinping Deng ◽  
Daniel George ◽  
...  
Keyword(s):  
Real Time ◽  
Radio Telescope ◽  
Phased Array ◽  
Single Pulse ◽  
Radio Bursts ◽  
Pulse Detection ◽  
Phased Array Feeds

AbstractThe challenges of detecting and localising Fast Radio Bursts in real time can be met with the use of Phased Array Feeds. One such system, capable of creating up to 36 simultaneous beams, is currently being commissioned at the Effelsberg radio telescope in Germany following testing at the 64 m Parkes radio telescope. The PAFINDER (Phased Array Feed FRB Finder) pipeline will be used with this receiver to enable real–time single–pulse detection and localisation.

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