Polarimetric observations

PHOTOMETRIC AND POLARIMETRIC OBSERVATIONS OF THE RV TAURI STAR AR PUPPIS... 

Photometric and Polarimetric Observations of the RV Tauri Star AR Pnppis... 

For levulose, the constants given are calculated from those of glucose and of invert sugar the marked variation of the rotation with the temperature and concentration renders polarimetric observations of this sugar somewhat inexact. 

If the polarimetric observations are made at a temperature t differing from 20°, allowance must be made for the variation of the rotatory power, especially for invert sugar in such cases, formula V is replaced by Clerget s formula 1 ... 

For the determination, 1-2 grams of the colouring matter are treated with about 95% alcohol and allowed to settle, the liquid being decanted off and the residue dissolved in a very small quantity of water and reprecipitated with alcohol the liquid is again decanted off and the residue washed with alcohol, dried at ioo° and weighed. That this consists of dextrin is confirmed by polarimetric observation of its aqueous solution. 

The aqueous solution is opalescent.—Aqueous solutions of glycogen show a variable but pronounced bluish-white opalescence this opalescence may be so great that 1 % solutions are unsuitable for polarimetric observations. Quantitative measurements of the turbidity of glycogen solutions have been used for estimation of the glycogen content of a solution (see pp. 268-9), and for determination of the molecular weight (see Section II). 

In this chapter we overview (1) the progress in telescopic and spacecraft observations of the opposition effects of some atmosphereless celestial bodies and (2) the problems in understanding the photometric and polarimetric properties of planetary regoliths at small phase angles. Since several reviews of photometric and polarimetric observations of the Moon, Mars, asteroids, and planetary satellites have been published [34-36], we focus on findings related predominantly to imaging photometry and polarimetiy of planetary surfaces with spacecraft and telescopic techniques. We consider also recent results concerning photometric and polarimetric observations of minor planets. 

Therefore in order to obtain the intrinsic polarization we have to correct Fobs for the interstellar and the instrumental components. The classical method of investigating interstellar polarization is through polarimetric observations of neighboring stars. The instrumental polarization depends on the optics of the telescope and the polarimeter and usually does not exceed a few tenths of a percent. The correction for Pinst demands regular observations of polarimetric standards collected in several papers (see e.g. Coyne et al. 1974 Tinbergen 1979 Whittet 1992). 

The broad-band polarimetric observations of a large number of PMS stars show, however, that the main source of their intrinsic polarization is the scattering of the stellar radiation by CS dust (Bastien 1985 Grinin et al. 1991). This conclusion follows from the wavelength dependence of the intrinsic polarization it is far from that observed in the classical Be stars where Thomson scattering dominates. Another argument in favor of... 

Repeated polarimetric observations of yoimg stars show that in many of them the observed polarization is variable (Vardanian 1964 Serkowski 1969). The variability is observed in the position angle, degree of polarization and the wavelength dependence of P and 6. Several mechanisms have been suggested for explanation of this variability One of them is the surface inhomogeneity of the young stars. 

Abstract. We present a historical review of polarimetric observations of planetary atmospheres, comets, atmosphereless solar system bodies, and terrestrial materials. We highlight the study of physical and optical parameters of planetary atmospheres. Polarimetric observations of the atmospheres of Venus, Mars, Jupiter and Saturn have made it possible to determine the real part of the refractive index and the cumulative size distribution function for the constituent cloud layers. We describe a simple and reliable method of quantifying absorptive cloud layers of the giant planets and predict the vertical stracture of aerosol layers of planetaiy atmospheres based on the analysis of observational spectropolarimetric data of contours of molecular absorption bands at the center of the planetaiy disk. The method is effective only when experimental data exist in a broad interval of phase angles. Using this method we can determine aerosol sizes in the atmospheres of Uranus and Neptune. 

The great interest in this topic was further demonstrated by the paper of Kattawar et al. [23], Several models of the vertical stractme of the cloud layer were analyzed using the Monte-Carlo method and polarimetric observations. Using homogeneous and inhomogeneous atmosphere models yielded the same real part of the refractive index and the same particle size. This fact seems to confirm Sobolev s hypothesis that linear polarization is mostly formed by single scattering within an optically thin top atmospheric layer. 

Ground-based polarimetric observations of some features on the planetary disk indicated the existence of a haze layer overlying the main cloud (especially in subauroral regions). This was confirmed by the results of photopolarimetric observations from Pioneer Venus [24]. The value of the effective radius of the haze particles was about 0.23 micrometers the value of the real part of the refractive index was the same as for the cloud particles. 

The valnes tir = 1.36 - 0.01, ro = 0.19 - 0.01 micrometers, and cr = 0.28 -0.02 [47, 58] were retrieved from analysis of ground-based polarimetric observations in the spectral interval 316 800 nm using the approximate multiple-scattering approach described above. The results agreed well with data from Pioneer-10 at a phase angle of 103 . 

Gehrels et al. [19] presented lesrrlts of polarimetric observations of Mercury at a = 53° —> 130° and in the spectral range 0.340 - 0.960 pm obtained in 1964-70 using different telescopes but the same polarimeter. They reveal a time variation of the polarization with an amplitude of about AP = 0.7%. However, the minimal and maximal polarizations are distant from each other by only 40° of longitude. The authors interpret this as a longitudinal dependence of polarization caused by variations of composition and/or smface structure. 

On the basis of wideband-filter polarimetry, Kiselev divided comets into two groups depending on the maximum degree of polarization at large phase angles [19-21]. He noted that such a distinction between comets is caused by an influence of the molecular emissions that fall within the wideband filters. The narrowband [34] and intermediateband [44] polarimetric observations of comets confirmed the existence of the two groups. Chernova et al. [34] indicated that a... 

Recently Mishchenko et al. [10] predicted that at small phase angles near opposition, asteroids produce a sharp narrow spike of the measurable linear polarization due to coherent backscattering of reciprocal rays (named Opposition Effect). This mechanism operates in planets, asteroids and comets. The polarimetric observations made recently by Rosenbush et al. [11] with 125cm telescope at the Crimean Astrophysical Observatory confirm this prediction. 

Figure 5. Spectrophotometric and polarimetric observations of the S-type Mira variable R And on 1973 June 22 [28],...

Polarimetric observations in the far ultraviolet can be performed only from outside the Earth atmosphere. An excellent review of polarimetry in the far ultraviolet from balloons, aircrafts and rockets through 1981 was given by Coffeen [38]. The brief review of information about the equipment and results obtained in the Wisconsin Ultraviolet Photo-Polarimetric Experiment (WUPPE) and with the Hubble Space Telescope (HST) has been published by Kucherov et al. [39]. 

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