scholarly journals Linear Polarization Properties of Pulsars at 35 & 327 MHz

2000 ◽  
Vol 177 ◽  
pp. 245-246
Author(s):  
Ashish Asgekar ◽  
A. A. Deshpande
Keyword(s):  
Fourier Analysis ◽  
Radio Telescope ◽  
Faraday Rotation ◽  
Linear Polarization ◽  
Broad Band ◽  
Spectral Domain ◽  
Spectral Modulation ◽  
Polarization Characteristics

Faraday Rotation of the plane of polarization of broad-band signals, during propagation through the intervening medium, manifests as quasi-sinusoidal spectral modulations when observed with a telescope sensitive to a single linear polarization. Such a modulation can be exploited to study linear polarization characteristics of pulsars (Suleimanova, Volodin, & Shitov, 1988; Smirnova & Boriakoff 1997, Ramkumar & Deshpande 1999 (RD99)). We have used our data on a few bright pulsars at 35 MHz (Asgekar & Deshpande 1999, elsewhere in this volume) and data obtained at 327 MHz using Ooty Radio Telescope (see RD99 for details), to study average linear polarization properties using this technique. The data obtained over 256 frequency channels were re-sampled in the spectral domain to make the Faraday modulation appear periodic, and then a simple Fourier analysis was performed to look for (ACF) features associated with the possible spectral modulation (see RD99 for the analysis details).

scholarly journals Changes in Polarization Position Angle across the Eclipse in the Double Pulsar System

2012 ◽  
Vol 8 (S291) ◽  
pp. 580-582
Author(s):  
R. Yuen ◽  
R. N. Manchester ◽  
M. Burgay ◽  
F. Camilo ◽  
M. Kramer ◽  
...  
Keyword(s):  
Radio Telescope ◽  
Faraday Rotation ◽  
Position Angle ◽  
Charge Densities

AbstractWe investigate the changes in polarization position angle in radiation from pulsar A around the eclipse in the Double Pulsar system PSR J0737-3039A/B at the 20 cm and 50 cm wavelengths using the Parkes 64-m radio telescope. The changes are ~ 2σ during and shortly after the eclipse at 20 cm but less significant at 50 cm. We show that the changes in position angle during the eclipse can be modelled by differential synchrotron absorption in the eclipse regions. Position angle changes after the eclipse are interpreted as Faraday rotation in the magnetotail of pulsar B. Implied charge densities are consistent with the Goldreich-Julian density, suggesting that the particle energies in the magnetotail are mildly relativistic.

scholarly journals Yebes 40 m radio telescope and the broad band Nanocosmos receivers at 7 mm and 3 mm for line surveys

2021 ◽  
Vol 645 ◽  
pp. A37
Author(s):  
F. Tercero ◽  
J. A. López-Pérez ◽  
J. D. Gallego ◽  
F. Beltrán ◽  
O. García ◽  
...  
Keyword(s):  
Radio Telescope ◽  
Signal To Noise Ratio ◽  
Broad Band ◽  
High Sensitivity ◽  
Lower Sensitivity ◽  
Molecular Chemistry ◽  
Long Baseline ◽  
New Instrumentation ◽  
Frequency Coverage ◽  
Technical Specifications

Context. Yebes 40 m radio telescope is the main and largest observing instrument at Yebes Observatory and is devoted to very long baseline interferometry (VLBI) and single-dish observations since 2010. It has been covering frequency bands between 2 GHz and 90 GHz in discontinuous and narrow windows in most cases in order to match the current needs of the European VLBI Network (EVN) and the Global Millimeter VLBI Array (GMVA). Aims. The Nanocosmos project, a European Union-funded synergy grant, has enabled an increase in the instantaneous frequency coverage of the Yebes 40 m radio telescope, making it possible to observe many molecular transitions with single tunings in single-dish mode. This reduces the observing time and maximises the output from the telescope. Methods. We present technical specifications of the recently installed 31.5−50 GHz (Q band) and 72−90.5 GHz (W band) receivers along with the main characteristics of the telescope at these frequency ranges. We observed IRC+10216, CRL 2688, and CRL 618, which harbour a rich molecular chemistry, to demonstrate the capabilities of the new instrumentation for spectral observations in single-dish mode. Results. Our results show the high sensitivity of the telescope in the Q band. The spectrum of IRC+10126 offers an unprecedented signal-to-noise ratio for this source in this band. On the other hand, the spectrum normalised by the continuum flux towards CRL 618 in the W band demonstrates that the 40 m radio telescope produces comparable results to those from the IRAM 30 m radio telescope, although with a lower sensitivity. The new receivers fulfil one of the main goals of Nanocosmos and open up the possibility to study the spectrum of different astrophysical media with unprecedented sensitivity.

Nonlinear Fourier Analysis for Shallow Water Waves

2021 ◽  
Author(s):  
Alfred R. Osborne
Keyword(s):  
Fourier Series ◽  
Fourier Analysis ◽  
Shallow Water ◽  
Nonlinear Wave ◽  
Water Waves ◽  
Wave Equations ◽  
Superposition Principle ◽  
Broad Band ◽  
Kp Equation ◽  
Linear Superposition

Abstract I consider nonlinear wave motion in shallow water as governed by the KP equation plus perturbations. I have previously shown that broad band, multiply periodic solutions of the KP equation are governed by quasiperiodic Fourier series [Osborne, OMAE 2020]. In the present paper I give a new procedure for extending this analysis to the KP equation plus shallow water Hamiltonian perturbations. We therefore have the remarkable result that a complex class of nonlinear shallow water wave equations has solutions governed by quasiperiodic Fourier series that are a linear superposition of sine waves. Such a formulation is important because it was previously thought that solving nonlinear wave equations by a linear superposition principle was impossible. The construction of these linear superpositions in shallow water in an engineering context is the goal of this paper. Furthermore, I address the nonlinear Fourier analysis of experimental data described by shallow water physics. The wave fields dealt with here are fully two-dimensional and essentially consist of the linear superposition of generalized cnoidal waves, which nonlinearly interact with one another. This includes the class of soliton solutions and their associated Mach stems, both of which are important for engineering applications. The newly discovered phenomenon of “fossil breathers” is also characterized in the formulation. I also discuss the exact construction of Morison equation forces on cylindrical piles in terms of quasiperiodic Fourier series.

Broad-Band Polarization Characteristics on Transmission and Reflection of Metal Array Structures in Terahertz Region

2018 ◽  
Vol 38 (5) ◽  
pp. 0513001
Author(s):  
沈云 Shen Yun ◽  
汪涛 Wang Tao ◽  
汪云 Wang Yun ◽  
邓晓华 Deng Xiaohua ◽  
曹俊诚 Cao Juncheng ◽  
...  
Keyword(s):  
Broad Band ◽  
Terahertz Region ◽  
Array Structures ◽  
Polarization Characteristics ◽  
Transmission And Reflection

Linear polarization characteristics for terrain identification at millimeter wave band

2014 ◽  
Vol 12 (10) ◽  
pp. 101201-101204
Author(s):  
Xuan Lu Xuan Lu ◽  
Zelong Xiao Zelong Xiao ◽  
Jianzhong Xu Jianzhong Xu
Keyword(s):  
Millimeter Wave ◽  
Linear Polarization ◽  
Wave Band ◽  
Millimeter Wave Band ◽  
Polarization Characteristics

scholarly journals The Radio Polarization of BL Lacertae: Shocks in a Jet

1984 ◽  
Vol 110 ◽  
pp. 119-120 ◽  
Author(s):  
Hugh D. Aller ◽  
Margo F. Aller
Keyword(s):  
Axial Compression ◽  
Faraday Rotation ◽  
Linear Polarization ◽  
Radio Bursts ◽  
Bl Lacertae

The behavior of the linear polarization of BL Lacertae during the recent series of radio bursts indicates the presence of Faraday rotation in the vicinity of the source and the formation of an axial compression in the radio jet.

scholarly journals Spectropolarimetric monitoring of WR140

1995 ◽  
Vol 163 ◽  
pp. 506-507
Author(s):  
R.E. Schulte-Ladbeck ◽  
K. H. Nordsieck ◽  
K. S. Bjorkman ◽  
M. R. Meade ◽  
B. L. Babler
Keyword(s):  
Detection Limit ◽  
Linear Polarization ◽  
Broad Band ◽  
Line Emission ◽  
Intrinsic Polarization ◽  
The Continuum

We report on eight years of spectropolarimetric monitoring of the WR140 binary. The broad-band linear polarization decreased systematically after the 1985 periastron passage. By 1991, it settled to a constant value at which it has remained through the 1993 periastron passage. We do not detect, in data taken after 1989, a line-effect in He II Λ4686. This suggests either that the continuum and the line emission scatter at the same region, or that any intrinsic polarization has been below our detection limit. We conclude that the presently observed polarization of WR140 is consistent with interstellar foreground polarization.

Broad-band linear polarization and magnetic intensification in rotating magnetic stars

1981 ◽  
Vol 249 ◽  
pp. 228 ◽  
Author(s):  
M. Landi Deglinnocenti ◽  
G. Calamai ◽  
E. Landi Deglinnocenti ◽  
P. Patriarchi
Keyword(s):  
Linear Polarization ◽  
Broad Band ◽  
Magnetic Stars
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