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 International multiwavelength campaigns on short-term variability of OB stars: optical polarimetry

1994 ◽  
Vol 162 ◽  
pp. 530-531
Author(s):  
D. McDavid
Keyword(s):  
Optical Spectroscopy ◽  
Linear Polarization ◽  
Wide Band ◽  
Be Stars ◽  
Short Term ◽  
Ob Stars ◽  
Intensive Monitoring ◽  
Polarization Measurements ◽  
Ultraviolet Observations ◽  
Short Term Variability

From 1986 through 1992, wide-band optical (B or V filter) linear polarization measurements of eight Be stars and seven O stars were obtained simultaneously with ultraviolet observations from IUE and worldwide ground-based optical spectroscopy and photometry in a series of campaigns designed to study the short-term variability of these objects. Each campaign consisted of intensive monitoring of a few carefully chosen stars over a period of several days and nights, with the greatest possible continuity subject to the limitations of instrument scheduling, weather, and the longitudes of the observing sites.

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 Across the Balmer Lines of Be and Shell Stars

1976 ◽  
Vol 70 ◽  
pp. 261-275 ◽  
Author(s):  
I. S. McLean ◽  
D. Clarke
Keyword(s):  
Line Profile ◽  
Linear Polarization ◽  
New Method ◽  
Degree Of Polarization ◽  
Be Stars ◽  
Intrinsic Polarization ◽  
Polarization Effects ◽  
Polarization Measurements ◽  
Balmer Lines ◽  
The Continuum

We have made linear polarization measurements of several Be and shell stars across the Hα and Hβ lines, all of the stars exhibiting polarization in the continuum, the emphasis here being on measurements made of ζ Tau, 48 Per, φ Per, and γ Cas. Three types of results ensue: some stars show no significant change of polarization across the Balmer features (e.g., 48 Per, X Per); some stars show a reduced polarization across the features (e.g., γ Cas, ζ Tau) indicating the presence of intrinsic polarization; some stars show a change in the degree of polarization but with a marked rotation of the direction of vibration (e.g., φ Per, 48 Lib) which can be attributed to a combination of non-aligned intrinsic (circumstellar) and interstellar polarizations. Interpretations of these results are discussed, and we demonstrate the potential power of line profile polarimetry/photometry as an important new method for separating intrinsic and interstellar polarization effects, thus enabling polarization observations to be used as a constraint on models of Be stars.

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 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 Spectropolarimetric Atlas of 61 Bright Northern Be Stars

2000 ◽  
Vol 175 ◽  
pp. 48-50 ◽  
Author(s):  
Karen S. Bjorkman ◽  
Marilyn R. Meade ◽  
Brian L. Babler
Keyword(s):  
Wavelength Range ◽  
Spectral Resolution ◽  
Wavelength Dependence ◽  
Be Stars ◽  
University Of Wisconsin ◽  
Time Period ◽  
Ccd Detector ◽  
Ccd Observations ◽  
Full Analysis ◽  
The University

AbstractWe are developing an atlas of spectropolarimetric observations of 61 bright northern Be stars obtained from 1989-94 using the halfwave polarimeter (HPOL) at the 0.9m telescope of the University of Wisconsin Pine Bluff Observatory (PBO). The data cover the wavelength range from about 3400-7600Å, with a spectral resolution of about 25Å. This atlas will contain all data (297 observations total) obtained as part of a survey program with HPOL during the time when the detector in use was a dual Reticon array; the survey observations with HPOL continue, using a new CCD detector which extends the spectral coverage out to 1.05μm and improves the spectral resolution to about 12Å. The CCD observations will be presented later in a second volume of the atlas.Only a brief summary of the findings of the survey from the first 5 years of the project is presented here. A full analysis of the data will be included in a paper to be published elsewhere. The general wavelength dependence of polarization for classical Be stars can be considered on the basis of these observations, and results on polarimetric variability are available. In particular, we find that 56% (20 of 36) of the Be stars observed 3 or more times from 1989-94 show significantly variable polarization at the level of 0.1% changes (inclusion of preliminary results from the continuing CCD survey indicates that the percentage is even higher). The timescales for these changes range from as short as night-to-night to as long as several months. Several of the stars showed evidence for polarimetric “outbursts” during the time period covered by the observations.

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