scholarly journals Polarization measurements of the polluted white dwarf G29-38

2020 ◽  
Vol 494 (4) ◽  
pp. 4591-4605 ◽  
Author(s):  
Daniel V Cotton ◽  
Jeremy Bailey ◽  
J E Pringle ◽  
William B Sparks ◽  
Ted von Hippel ◽  
...  
Keyword(s):  
High Precision ◽  
Linear Polarization ◽  
White Dwarf ◽  
Position Angle ◽  
Polarization Signal ◽  
Polarization Measurements ◽  
Thin Disc ◽  
Measured Polarization ◽  
Dust Distribution

ABSTRACT We have made high-precision polarimetric observations of the polluted white dwarf G29-38 with the HIgh Precision Polarimetric Instrument 2. The observations were made at two different observatories – using the 8.1-m Gemini North Telescope and the 3.9-m Anglo-Australian Telescope – and are consistent with each other. After allowing for a small amount of interstellar polarization, the intrinsic linear polarization of the system is found to be 275.3 ± 31.9 parts per million at a position angle of 90.8 ± 3.8° in the SDSS g′ band. We compare the observed polarization with the predictions of circumstellar disc models. The measured polarization is small in the context of the models we develop, which only allows us to place limits on disc inclination and Bond albedo for optically thin disc geometries. In this case, either the inclination is near-face-on or the albedo is small – likely in the range 0.05–0.15 – which is in line with other debris disc measurements. A preliminary search for the effects of G29-38’s pulsations in the polarization signal produced inconsistent results. This may be caused by beating effects, indicate a clumpy dust distribution, or be a consequence of measurement systematics.

scholarly journals Variation of linear polarization in R Aquarii system

1987 ◽  
Vol 122 ◽  
pp. 475-476
Author(s):  
M. R. Deshpande ◽  
U. C. Joshi ◽  
A. K. Kulshrestha
Keyword(s):  
Time Dependence ◽  
Linear Polarization ◽  
Position Angle ◽  
Indian Institute ◽  
Symbiotic System ◽  
Circumstellar Material ◽  
Polarization Measurements ◽  
Dual Channel ◽  
Percent Polarization ◽  
R Aquarii

R Aquarii is a very interesting symbiotic system. There is an emission nebulosity close to the star which extends in North-South direction and a “jet” feature of about 6″ with a position angle of 29° has also been observed (Sopka et al. 1982; Mauron et al. 1985; Kafatos et al. 1983). Polarization measurements are important to understand the peculiar geometry of the circumstellar material around the central objects. Wavelength and time dependence of polarization can be used to put constraints on the geometry of the object and to identify the mechanism(s) responsible for polarization. In view of this linear polarization measurements of R Aquarii were carried out by us in UBVRI bands. Observations were made during November-December 1984 on 1 meter telescope of Indian Institute of Astrophysics, Bangalore, with a dual channel photo polarimeter discussed elsewhere (Deshpande et al. 1985). Measured values of percent polarization and position angle at different phases alongwith the earlier observations of Serkowski (1974) and Ladbeck (1985) are plotted in Figure 1.

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.

Linear polarization measurements by Ge(Li) detector

1969 ◽  
Vol 19 (10) ◽  
pp. 1281-1289 ◽  
Author(s):  
J. Honzátko ◽  
J. Kajfosz
Keyword(s):  
Linear Polarization ◽  
Polarization Measurements

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 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 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).

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