Circular polarization in the radio emission of RS canum venaticorum binaries

1995 ◽  
Vol 444 ◽  
pp. 342 ◽  
Author(s):  
Stephen M. White ◽  
Elena Franciosini
Keyword(s):  
Radio Emission ◽  
Circular Polarization ◽  
Rs Canum Venaticorum Binaries

scholarly journals A circular polarization survey for radio stars with the Australian SKA Pathfinder

2021 ◽  
Vol 502 (4) ◽  
pp. 5438-5454
Author(s):  
Joshua Pritchard ◽  
Tara Murphy ◽  
Andrew Zic ◽  
Christene Lynch ◽  
George Heald ◽  
...  
Keyword(s):  
Radio Emission ◽  
Brightness Temperature ◽  
Circular Polarization ◽  
Flux Density ◽  
Wide Band ◽  
M Dwarfs ◽  
Square Kilometre Array ◽  
Population Statistics ◽  
Chemically Peculiar ◽  
Radio Stars

ABSTRACT We present results from a circular polarization survey for radio stars in the Rapid ASKAP Continuum Survey (RACS). RACS is a survey of the entire sky south of δ = +41○ being conducted with the Australian Square Kilometre Array Pathfinder telescope (ASKAP) over a 288 MHz wide band centred on 887.5 MHz. The data we analyse include Stokes I and V polarization products to an RMS sensitivity of 250 μJy PSF−1. We searched RACS for sources with fractional circular polarization above 6 per cent, and after excluding imaging artefacts, polarization leakage, and known pulsars we identified radio emission coincident with 33 known stars. These range from M-dwarfs through to magnetic, chemically peculiar A- and B-type stars. Some of these are well-known radio stars such as YZ CMi and CU Vir, but 23 have no previous radio detections. We report the flux density and derived brightness temperature of these detections and discuss the nature of the radio emission. We also discuss the implications of our results for the population statistics of radio stars in the context of future ASKAP and Square Kilometre Array surveys.

scholarly journals Polarization in Pulsar Radio Emission

1992 ◽  
Vol 128 ◽  
pp. 384-386
Author(s):  
D. M. GOULD
Keyword(s):  
Radio Emission ◽  
Circular Polarization ◽  
Linear Polarization ◽  
Large Data ◽  
Position Angle ◽  
Published Data ◽  
Data Set ◽  
Pulsar Radio ◽  
Polarization Profiles ◽  
Pulsar Radio Emission

Polarimetric observations of over 300 pulsars have been carried out between 21 December 1988 and 22 January 1990 at 606, 610, 925, and 1408 MHz using the Lovell Telescope at Jodrell Bank. Many of these pulsars have no previously published polarization profiles and will be published shortly (Gould and Lyne 1990). This large data set along with previously published data from various sources, has been used to test the correlation found by Radhakrishnan and Rankin (1990) between sense reversing circular polarization signatures and the accompanying sense of rotation of the linear polarization position angle.

scholarly journals On the Nature of the Circularly Polarized Component of Pulsar Radio Emission

1992 ◽  
Vol 128 ◽  
pp. 375-377 ◽  
Author(s):  
Ya. N. Istomin
Keyword(s):  
Radio Emission ◽  
Circular Polarization ◽  
Polar Cap ◽  
Core Component ◽  
Pulsar Radio ◽  
Left Hand ◽  
Polarized Waves ◽  
The Magnetic Field ◽  
Group Velocities ◽  
Pulsar Radio Emission

AbstractIt is shown that circular polarization occurs in the region of cyclotron resonance because the group velocities of right-hand and left-hand polarized waves are different with respect to the direction of the magnetic field. Due to the dependence of the intensity of radio emission on the coordinates across the polar cap, this difference in group velocities leads to noncompensated circular polarization proportional to the derivative of the total intensity as a function of longitude. The indicated dependence corresponds to observations of the so-called core component of pulsar radio emission.

scholarly journals What is shaping the planetary nebula K3-35?

2010 ◽  
Vol 6 (S275) ◽  
pp. 414-415
Author(s):  
Y. Gómez ◽  
D. Tafoya ◽  
G. Anglada ◽  
L. F. Miranda ◽  
L. Uscanga ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Water Vapor ◽  
Radio Emission ◽  
Circular Polarization ◽  
Large Distance ◽  
Planetary Nebula

AbstractK 3-35 is a very young planetary nebula (PN) with a characteristic S-shaped radio emission morphology. It is the first PN where water vapor maser was detected: the emission is located in a torus-like structure with a radius of 100 AU and also at the surprisingly large distance of 5000 AU from the star, in the tips of the bipolar lobes. Several mechanism have been proposed to explain the bipolar morphology of PNe, and in the case of K 3-35 we believe we may be observing several of them at the same time: i) a disk-like structure traced by the H2O masers, ii) a precessing bipolar jet probably due to the presence of a binary companion and iii) circular polarization in the OH 1665 MHz masers, which suggests the presence of a magnetic field. Additional observations and modeling are needed to establish what mechanisms are shaping K 3-35.

scholarly journals On the beam properties of radio pulsars with interpulse emission

2019 ◽  
Vol 490 (4) ◽  
pp. 4565-4574 ◽  
Author(s):  
Simon Johnston ◽  
Michael Kramer
Keyword(s):  
Radio Emission ◽  
Circular Polarization ◽  
Visible Emission ◽  
Radio Pulsars ◽  
Polarization Data ◽  
Substantial Evidence ◽  
High Quality ◽  
Emission Beam ◽  
Average Profile ◽  
Better Than

ABSTRACT In the canonical picture of pulsars, radio emission arises from a narrow cone centred on the star’s magnetic axis but many basic details remain unclear. We use high-quality polarization data taken with the Parkes radio telescope to constrain the geometry and emission heights of pulsars showing interpulse emission, and include the possibility that emission heights in the main and interpulse may be different. We show that emission heights are low in the centre of the beam, typically less than 3 per cent of the light cylinder radius. The emission beams are underfilled in longitude, with an average profile width only 60 per cent of the maximal beamwidth and there is a strong preference for the visible emission to be located on the trailing part of the beam. We show substantial evidence that the emission heights are larger at the beam edges than in the beam centre. There is some indication that a fan-like emission beam explains the data better than conal structures. Finally, there is a strong correlation between handedness of circular polarization in the main and interpulse profiles, which implies that the hand of circular polarization is determined by the hemisphere of the visible emission.

scholarly journals Predicting the time variation of radio emission from MHD simulations of a flaring T-Tauri star

2020 ◽  
Vol 496 (3) ◽  
pp. 2715-2725
Author(s):  
C O G Waterfall ◽  
P K Browning ◽  
G A Fuller ◽  
M Gordovskyy ◽  
S Orlando ◽  
...  
Keyword(s):  
Radio Emission ◽  
Circular Polarization ◽  
Flux Tube ◽  
Thermal Power ◽  
Complex Structure ◽  
Tauri Star ◽  
Transfer Model ◽  
T Tauri ◽  
Heating Event ◽  
Peak Flux

ABSTRACT We model the time-dependent radio emission from a disc accretion event in a T-Tauri star using 3D, ideal magnetohydrodynamic simulations combined with a gyrosynchrotron emission and radiative transfer model. We predict for the first time, the multifrequency (1–1000 GHz) intensity and circular polarization from a flaring T-Tauri star. A flux tube, connecting the star with its circumstellar disc, is populated with a distribution of non-thermal electrons that is allowed to decay exponentially after a heating event in the disc and the system is allowed to evolve. The energy distribution of the electrons, as well as the non-thermal power-law index and loss rate, are varied to see their effect on the overall flux. Spectra are generated from different lines of sight, giving different views of the flux tube and disc. The peak flux typically occurs around 20–30 GHz and the radio luminosity is consistent with that observed from T-Tauri stars. For all simulations, the peak flux is found to decrease and move to lower frequencies with elapsing time. The frequency-dependent circular polarization can reach 10$-30{{\ \rm per\ cent}}$ but has a complex structure that evolves as the flare evolves. Our models show that observations of the evolution of the spectrum and its polarization can provide important constraints on physical properties of the flaring environment and associated accretion event.

scholarly journals Measurement of the circular polarization in radio emission from extensive air showers confirms emission mechanisms

2016 ◽  
Vol 94 (10) ◽  
Author(s):  
O. Scholten ◽  
T. N. G. Trinh ◽  
A. Bonardi ◽  
S. Buitink ◽  
P. Correa ◽  
...  
Keyword(s):  
Radio Emission ◽  
Circular Polarization ◽  
Extensive Air Showers ◽  
Air Showers

Radio Emission from Starspots on RSCVn Binary HR1099

1986 ◽  
Vol 6 (3) ◽  
pp. 316-319 ◽  
Author(s):  
John D. Bunton ◽  
R. T. Stewart ◽  
O. B. Slee ◽  
G. J. Nelson ◽  
Alan E. Wright ◽  
...  
Keyword(s):  
Synchrotron Radiation ◽  
Magnetic Fields ◽  
Radio Emission ◽  
Light Curve ◽  
Circular Polarization ◽  
Rotation Rate ◽  
Source Model ◽  
Microwave Emission ◽  
Relativistic Electrons ◽  
Synchrotron Source

AbstractProperties of the microwave emission from HR1099 are examined in an attempt to determine whether the emission arises as gyro-synchrotron radiation from mildly relativistic electrons trapped in magnetic fields above starspots on the active K subgiant component. It is shown that radio curves do not exhibit a systematic variation in phase with the rotation rate, as one might expect for emission from a source situated above a long-lived starspot. However, there is some evidence that the radio flaring occurs at two preferred longitude zones. Whether these zones agree with starspot locations remains to be determined by light curve modelling. What we can say with confidence is that the measured spectral index of the microwave emission does not fit a simple gyro-synchrotron source model, such as that proposed to explain the observed reversal with frequency of the sense of circular polarization.

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