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 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 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 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.

scholarly journals A low-mass stellar companion to the young variable star RZ Psc

2020 ◽  
Vol 496 (1) ◽  
pp. L75-L79
Author(s):  
Grant M Kennedy ◽  
Christian Ginski ◽  
Matthew A Kenworthy ◽  
Myriam Benisty ◽  
Thomas Henning ◽  
...  
Keyword(s):  
Linear Polarization ◽  
Variable Star ◽  
Orbital Motion ◽  
Orbital Plane ◽  
Position Angle ◽  
Circumstellar Dust ◽  
Primary Star ◽  
Infrared Excess ◽  
Low Mass ◽  
Rz Psc

ABSTRACT RZ Psc is a young Sun-like star with a bright and warm infrared excess that is occasionally dimmed significantly by circumstellar dust structures. Optical depth arguments suggest that the dimming events do not probe a typical sightline through the circumstellar dust, and are instead caused by structures that appear above an optically thick mid-plane. This system may therefore be similar to systems where an outer disc is shadowed by material closer to the star. Here, we report the discovery that RZ Psc hosts a $0.12\, \mathrm{ M}_\odot$ companion at a projected separation of 23 au. We conclude that the disc must orbit the primary star. While we do not detect orbital motion, comparison of the angle of linear polarization of the primary with the companion’s on-sky position angle provides circumstantial evidence that the companion and disc may not share the same orbital plane. Whether the companion severely disrupts the disc, truncates it, or has little effect at all will require further observations of both the companion and disc.

scholarly journals A Multi-Frequency VLBI Total Intensity and Polarization Study of the BL Lacertae Object 0716+714

1998 ◽  
Vol 164 ◽  
pp. 173-174
Author(s):  
Y. Y. Kovalev ◽  
D. C. Gabuzda ◽  
T. P. Krichbaum ◽  
W. Alef ◽  
A. Witzel
Keyword(s):  
Linear Polarization ◽  
Position Angle ◽  
Published Data ◽  
Apparent Velocity ◽  
Structural Position ◽  
Core Polarization ◽  
Bl Lacertae ◽  
Polarization Study ◽  
Intensity Image ◽  
Jet Structure

AbstractNew polarization-sensitive global VLBI and VLBA images of the BL Lacertae object 0716+714 at 6 cm (1991.4) and 3.6 cm/1.3 cm (1994.2) are presented. The source shows a compact, one-sided core–jet structure in structural position angle ~ 13°. The 3.6 cm total intensity image shows the jet beginning to curve toward the arcsecond-scale structure, which lies in position angle ~ −45°. Comparison with previously published data suggests that the apparent velocity of a 6 cm jet component is > 1.09 ± 0.15c, if the red shift of 0716+714 is z > 0.3. Linear polarization from the VLBI core was detected at all three frequencies; in addition, polarization from the innermost jet component was detected at 1.3 cm. This compact jet polarization appears to be quite high, ~ 50%, and to be aligned with the jet direction, which can be understood if it is a transverse shock. The VLBI core polarization at our earlier epoch was perpendicular to the VLBI jet direction, but had rotated to align with the jet direction by the later epoch, about a year later. This rotation may indicate the imminent birth of a new VLBI component (shock).

Ultraviolet interstellar linear polarization. 2: The wavelength dependence

1995 ◽  
Vol 445 ◽  
pp. 947 ◽  
Author(s):  
Geoffrey C. Clayton ◽  
Michael J. Wolff ◽  
R. G. Allen ◽  
O. L. Lupie
Keyword(s):  
Linear Polarization ◽  
Wavelength Dependence

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.

scholarly journals Direct Imaging of Planet Transit Events

2012 ◽  
Vol 8 (S293) ◽  
pp. 378-381
Author(s):  
Gerard T. van Belle ◽  
Kaspar von Braun ◽  
Tabetha Boyajian ◽  
Gail Schaefer
Keyword(s):  
Wavelength Dependence ◽  
Position Angle ◽  
Atmospheric Composition ◽  
Optical Interferometer ◽  
Direct Imaging ◽  
Stellar Radius ◽  
System Parameters ◽  
Optical Interferometers ◽  
Host Stars

AbstractExoplanet transit events are attractive targets for the ultrahigh-resolution capabilities afforded by optical interferometers. The intersection of two developments in astronomy enable direct imaging of exoplanet transits: first, improvements in sensitivity and precision of interferometric instrumentation; and second, identification of ever-brighter host stars. Efforts are underway for the first direct high-precision detection of closure phase signatures with the CHARA Array and Navy Precision Optical Interferometer. When successful, these measurements will enable recovery of the transit position angle on the sky, along with characterization of other system parameters, such as stellar radius, planet radius, and other parameters of the transit event. This technique can directly determine the planet's radius independent of any outside observations, and appears able to improve substantially upon other determinations of that radius; it will be possible to extract wavelength dependence of that radius determination, for connection to characterization of planetary atmospheric composition & structure. Additional directly observed parameters - also not dependent on transit photometry or spectroscopy - include impact parameter, transit ingress time, and transit velocity.

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