scholarly journals Simultaneous Five Color (UBVRI) Polarimetry of VV Puppis

1987 ◽  
Vol 93 ◽  
pp. 203-203
Author(s):  
V. Piirola ◽  
A. Reiz ◽  
G.V. Coyne
Keyword(s):  
Circular Polarization ◽  
Linear Polarization ◽  
Wavelength Dependence ◽  
Position Angle ◽  
Orbital Inclination ◽  
V Band ◽  
Highly Active ◽  
Phase Interval ◽  
In The Beginning ◽  
Bright Phase

AbstractObservations of linear and circular polarization in five colour bands during a highly active state of VV Puppis in January 86 are reported. A strong linear polarization pulse with the maximum in the blue, PB ≈ 22%, is observed at the end of the bright phase when the active pole is at the limb and a weaker secondary pulse, PB ≈ 7%, is seen in the beginning of the bright phase, when the active pole reappears. Strong positive circular polarization is also observed in the blue and the ultraviolet, РU ≈ PB ≈ 18%, PV ≈ 10% during the bright phase. The circular polarization reverses the sign in the B and V bands during the faint phase and a negative polarization hump is seen when the active pole crosses the limb. The circular polarization in the V band reaches the value PV ≈ −10% at the hump, after which it remains near PV ≈ −5% during the faint phase. This is probably due to radiation coming from the second, less active pole and accretion thus takes place onto both poles. The wavelength dependences of the positive and negative parts of the circular polarization curve are different and no polarization reversal is seen in the U band. The position angle of the linear polarization is well determined during a large portion of the cycle, especially in the V band, thanks to the activity from both poles. A best fit to the position angle curve, taking into account also the duration of the positive circular polarization phase interval ΔΦ = 0.40 (in the V band), yields the values of orbital inclination i = 78° ± 2° and the colatitude of the active magnetic pole ß = 146° ± 2°. The relatively good fit to the position angle data indicates that the simple dipole model is nearly correct in the case of VV Puppis. Some wavelength dependence is, however, seen in the position angle curves, especially in the I band where the slope Δθ/ΔΦ at the main pulse is considerably smaller than in the other bands. The shape of the position angle curves changes also in the blue and the ultraviolet around the middle of the bright phase. This is probably due to optical thickness effects as the side of the accretion column which is toward the observer changes near this phase.

scholarly journals Interstellar Circular Polarization and the Composition of Interstellar Dust

1973 ◽  
Vol 52 ◽  
pp. 161-167 ◽  
Author(s):  
P. G. Martin
Keyword(s):  
Circular Polarization ◽  
Linear Polarization ◽  
Interstellar Dust ◽  
Principal Axis ◽  
Complex Refractive Index ◽  
Polarized Light ◽  
Position Angle ◽  
Optical Observations ◽  
Small Component ◽  
Linearly Polarized

This paper shows that optical observations of circular polarization produced by aligned interstellar grains could yield valuable information about the grain material. The interstellar medium is known to be linearly dichroic from observations of interstellar linear polarization; many different grain models using a large variety of compositions can be found to reproduce these observations. Since the same aligned grains make the medium linearly birefringent, a small component of circular polarization can result from incident linearly polarized light if the position angle of the linear polarization does not coincide with either principal axis of the medium. Here calculations are presented to demonstrate that the wavelength of the circular polarization is sensitive to the imaginary part of the complex refractive index of the grain material. This provides an opportunity of investigating whether the grains are characteristically dielectric or metallic. Some possible observations are suggested.

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.

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).

scholarly journals Polarization Variability of Some Compact Radio Sources

1982 ◽  
Vol 97 ◽  
pp. 331-333
Author(s):  
M. M. Komesaroff ◽  
D. K. Milne ◽  
P. T. Rayner ◽  
J. A. Roberts ◽  
D. J. Cooke
Keyword(s):  
Circular Polarization ◽  
Linear Polarization ◽  
Position Angle ◽  
Linear Increase ◽  
Monitoring Programme ◽  
Radio Sources ◽  
List Type ◽  
Type Number ◽  
5 Ghz ◽  
Superluminal Expansion

Figure 1 shows observations for four sample sources from the Parkes 5 GHz polarization monitoring programme. Interesting features illustrated include •Sudden changes of the position angle of the linear polarization by ≳ 70° in PKS 0537-441 and 1253-055 (3C279).•A linear increase in the position angle of the polarization of PKS 2134+004 through 70° over 3/12; years.•Distinct bursts of circular polarization in PKS 0430+052, 0537-441 and 1253-055. In PKS 0430+052 (3C120) such a burst coincides with the possible superluminal expansion (Walker et al., 1981). In PKS 1253-055 (3C279) a burst of circular polarization is currently occurring at a time of very low linear polarization.

scholarly journals Low optical polarization at the core of the optically thin jet of M87

2020 ◽  
Vol 496 (2) ◽  
pp. 2204-2212
Author(s):  
A Y Fresco ◽  
J A Fernández-Ontiveros ◽  
M A Prieto ◽  
J A Acosta-Pulido ◽  
A Merloni
Keyword(s):  
Circular Polarization ◽  
Linear Polarization ◽  
Position Angle ◽  
Field Configuration ◽  
Stokes Parameters ◽  
No Emission ◽  
The Core ◽  
Level Of Activity ◽  
High Degree ◽  
Disordered Magnetic

ABSTRACT We study the optical linear and circular polarization in the optically thin regime of the core and jet of M87. Observations were acquired two days before the Event Horizon Telescope (EHT) campaign in early 2017 April. A high degree (∼20 per cent) of linear polarization (Plin) is detected in the bright jet knots resolved at $\sim 10\,\mathrm{ to}\,23\, \rm {arcsec}$ ($0.8{-}1.8\, \rm {kpc}$) from the centre, whereas the nucleus and inner jet show Plin ≲ 5 per cent. The position angle of the linear polarization shifts by ∼90° from each knot to the adjacent ones, with the core angle perpendicular to the first knot. The nucleus was in a low level of activity (Plin ∼ 2–3 per cent), and no emission was detected from HST-1. No circular polarization was detected either in the nucleus or the jet above a 3 σ level of Pcirc ≤ 1.5 per cent, discarding the conversion of Plin into Pcirc. A disordered magnetic field configuration or a mix of unresolved knots polarized along axes with different orientations could explain the low Plin. The latter implies a smaller size of the core knots, in line with current interferometric observations. Polarimetry with EHT can probe this scenario in the future. A steep increase of both Plin and Pcirc with increasing frequency is expected for the optically thin domain, above the turnover point. This work describes the methodology to recover the four Stokes parameters using a λ/4 waveplate polarimeter.

scholarly journals Polarization measurements of some T Tauri stars

1987 ◽  
Vol 122 ◽  
pp. 135-136
Author(s):  
U. C. Joshi ◽  
M. R. Deshpande ◽  
A. K. Kulshrestha
Keyword(s):  
Systematic Study ◽  
Linear Polarization ◽  
Wavelength Dependence ◽  
Position Angle ◽  
T Tauri Stars ◽  
Time Variability ◽  
Specific Mechanism ◽  
Polarization Measurements ◽  
T Tauri ◽  
University Of Arizona

T Tauri stars show linear polarization typically between 1–3%. A two band linear polarization survey of some T Tauri star was reported earlier by Bastien (1982). Most of the stars show pronounced time variability in polarization and position angle (Bastien, 1980; 1982). Wavelength dependence of polarization is important in determining the specific mechanism(s) producing polarization. For a systematic study of polarization in T Tauri stars, we have taken up an observing programme to measure linear polarization of some stars in Taurus-Auriga region. Polarization measurements of 9 T Tauri stars are reported here. Observations were made on January 8–11, 1984 with MINIPOL (Frecker and Serkowski, 1976) on 61“ telescope of University of Arizona.

scholarly journals Polarimetry of CH Cygni

1982 ◽  
Vol 70 ◽  
pp. 139-140
Author(s):  
V. Piirola
Keyword(s):  
Particle Size ◽  
Electron Scattering ◽  
Linear Polarization ◽  
Wavelength Dependence ◽  
Position Angle ◽  
Yellow Light ◽  
Infrared Observations ◽  
Dust Envelope ◽  
Scattering Geometry

Variable linear polarization has been detected in CH Cyg. Observations in 1977–79 (UBV) and 1979–80 (UBVRI) are presented. The amount of polarisation increases towards ultraviolet and the observed values range from 0.34 to 1 .85 % in the ultraviolet, and 0.04 to 0.68 % in the yellow light. In the red and infrared observations the polarizationwas typically less than 0.1 %. During the interval September 1977 – February 1978 and in May 1980 a second component of polarization, with different direction and wavelength dependence, was present, resulting in a strong rotation of the position angle as a function of wavelength. The R and I observations of May 1980 (PR ≅ 0.4 %, PI ≅ 0.5%) showed that the second component was increasing towards the infrared. The peculiar wavelength dependence of polarization and position angle could be explained by variations in particle size and scattering geometry in a complicated dust envelope around the M giant. Another hypothesis is that the component of polarization increasing towards the ultraviolet is produced by electron scattering in an extended envelope of a hot companion and the second component by transient dust envelope of the M giant.

scholarly journals Broadband Linear Polarization in Ap Stars

1993 ◽  
Vol 138 ◽  
pp. 305-309
Author(s):  
Marco Landolfi ◽  
Egidio Landi Degl’Innocenti ◽  
Maurizio Landi Degl’Innocenti ◽  
Jean-Louis Leroy ◽  
Stefano Bagnulo
Keyword(s):  
Magnetic Field ◽  
Circular Polarization ◽  
Linear Polarization ◽  
Rotation Axis ◽  
Spectral Lines ◽  
Line Of Sight ◽  
Long Time ◽  
Rotating Star ◽  
Ap Stars ◽  
The Magnetic Field

AbstractBroadband linear polarization in the spectra of Ap stars is believed to be due to differential saturation between σ and π Zeeman components in spectral lines. This mechanism has been known for a long time to be the main agent of a similar phenomenon observed in sunspots. Since this phenomenon has been carefully calibrated in the solar case, it can be confidently used to deduce the magnetic field of Ap stars.Given the magnetic configuration of a rotating star, it is possible to deduce the broadband polarization at any phase. Calculations performed for the oblique dipole model show that the resulting polarization diagrams are very sensitive to the values of i (the angle between the rotation axis and the line of sight) and β (the angle between the rotation and magnetic axes). The dependence on i and β is such that the four-fold ambiguity typical of the circular polarization observations ((i,β), (β,i), (π-i,π-β), (π-β,π-i)) can be removed.

scholarly journals Polarization Measurements of Some Herbig Ae/Be Stars

1990 ◽  
Vol 140 ◽  
pp. 323-324
Author(s):  
S. K. Jain ◽  
H.C. Bhatt ◽  
Ram Sagar
Keyword(s):  
Linear Polarization ◽  
Wavelength Dependence ◽  
Be Stars ◽  
Polarization Measurements

We have measured the linear polarization of 8 bright Herbig Ae/Be stars in UBVRI bands. No unique wavelength dependence of polarization magnitude as well as direction is found in these measurements.

Polarization Reconfigurable Dual-Band Rectangular Slot Antenna

Frequenz ◽  
2019 ◽  
Vol 73 (9-10) ◽  
pp. 339-351
Author(s):  
Rohit Kumar Saini
Keyword(s):  
Circular Polarization ◽  
Linear Polarization ◽  
Dual Band ◽  
Slot Antenna ◽  
Pin Diodes ◽  
Rectangular Slot ◽  
Left Hand ◽  
Right Hand ◽  
Lower Band ◽  
The Senses

Abstract A novel dual-band rectangular slot antenna is presented for dual-sense reconfigurable polarization. A W-shaped microstrip feedline and two rectangular parasitic patches are used to obtain dual-band circular polarization. Further, the feedline is modified so that the senses of polarization at the two bands are opposite. By introducing PIN-diodes in the feed lines, polarization can be switched among left-hand circular polarization (LHCP), right-hand circular polarization (RHCP), and linear polarization (LP). A prototype dual-band dual-sense antenna with f01 = 1.9 GHz and f02 = 3.45 GHz is fabricated in a 1.6 mm thick FR4 substrate. The measured circular polarized bandwidths are more than 7.6 % for the lower band and 5 % for the upper band.

Sign in / Sign up

Export Citation Format

Share Document