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1.

The results of the first polarimetric measurements of near-Earth asteroid 2014 JO25 and comet 41P/Tuttle-Giacobini-Kresák performed on April 19, 2017, with a CCD sensor at the prime focus (f/3.85) of the 2.6-m Shajn Telescope of the Crimean Astrophysical Observatory in the R filter are reported. The degree of linear polarization of the asteroid is P = 2.69 ± 0.44% at a phase angle of 55.6°, which is typical of an S-type asteroid. Its geometric albedo is ρv ≈ 0.2. A digital filter applied to the direct image of the comet reveals a jet and a tail directed toward the Sun (PA = 45.1°) and away from it (PA = 241.2°), respectively, in the coma. The maximum degree of linear polarization in the near-nucleus region of the comet is 18% at a phase angle of 69.8°. The polarization decreases to 16.2–10.7% in coma regions with a radius of 865–4856 km. Various factors affecting the maximum degree of polarization and the polarization-degree distribution over the coma are discussed.

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2.
The results of photometry and polarimetry of the R Coronae Borealis type stars and other interesting objects are given. The observation of the former objects are obtained at the light maximum or at a brightness lower by 2-3 mag. The polarization of R CrB stars at light maximum has interstellar origin. The absolute magnitude of V 854 Cen is estimated to Msvw = −3m, and for Y Mus it is Mv > −3m.7. ρ Cas has a variable polarization and is probably a giant (Mv ≅ 0m) rather than a supergiant. Many early stars in its surroundings are photometrically and polarimetrically variable. The protoplanetary star BD −0°3679 has a polarization with the Rayleigh component.  相似文献   

3.
The results of the spectrophotometrical measurements of the polarization in the coronal lines Fe xiv 5303 Å and Fe × 6374 Å are given. Polarization spectrograms were obtained by two spectrographs (prism and echelle types) during the solar eclipse in Mexico on 7 March, 1970 near the region of the second contact at the heights 0.06 to 0.12 R above the limb. The polarization in the green line is about 30% (for averaged height 1.08 R ). The polarization in the red line is close to the errors of the measurement and does not exceed 6%. A brief discussion of the results is also given.  相似文献   

4.
The results of multicolor photopolarimetric observations of the Ae/Be Herbig star V628 Cas are presented. It has been shown that the observed changes of the linear polarization correlate with the phase of the orbital period. The system demonstrated changes in brightness, the amplitude of which decreases from 0.4 to 0.1m when moving from the U band to the I band. No dependence of the polarization degree on the brightness is observed.  相似文献   

5.
In this paper we summarize and analyze the results of observation of linear polarization of H α emission for solar flares and moustaches obtained earlier. Basic structural and evolutional properties of the observed polarization are formulated and presented. A conclusion is drawn that polarization data obtained from rough time and spatial averaging of Stokes parameters distort the true picture of polarization of H α emission in flares and moustaches.  相似文献   

6.
The propagation of an instantaneous burst of nonpolarized isotropic radiation from the time of its onset at some redshift z 0 to the time of its recording at the present epoch is considered within the framework of a flat cosmological model. Thomson (Rayleigh) scattering by free electrons is believed to be the only source of opacity. The spatial distributions of the mean (over the directions) radiation intensity as well as the angular distributions of the radiation intensity and polarization at various distances from the burst center have been constructed. The mean intensity profile normalized to the total number of photons emitted during the burst is shown to depend weakly on the initial conditions (the burst time z 0, the width and shape of the initial radiation distribution) at fairly high z 0 (≥1400). As regards the angular intensity and polarization distributions, they turn out to be rather narrow (3–10 arcmin), while the polarization can reach 70%. On average, the expected polarization can be about 15%.  相似文献   

7.
Stenflo  J. O. 《Solar physics》1974,37(1):31-42
The resonance polarization in Ca i 4226.73 has been measured close to the solar limb for three values of = cos. The polarization has maxima in the wings at about –500 and + 400 mÅ from the line center, the plane of polarization (electric vector) being parallel to the solar limb. The blue wing is more polarized than the red wing, contrary to earlier results of Brückner (1963). Local minima in the polarization curves occur at the position of blends. The polarization in the wings increases rapidly with decreasing . At = 0.15 the maximum polarization in the blue wing is about 2.4%.The observations are in good qualitative agreement with the recent theory of Dumont et al. (1973), but the observed polarization degrees are significantly smaller than the computed values. This may be explained by the inadequate formula for van der Waals broadening used in the theoretical calculations. Much of the discrepancies between observed and computed values disappear if the recent value of Lites (1974) for the collisional damping constant is used. Further improvements in theory and observation are discussed.  相似文献   

8.
We present the first determination of the Galactic polarized emission at 353 GHz by Archeops. The data were taken during the Arctic night of February 7, 2002 after the balloon-borne instrument was launched by CNES from the Swedish Esrange base near Kiruna. In addition to the 143 and 217 GHz frequency bands dedicated to CMB studies, Archeops had one 545 GHz and six 353 GHz bolometers mounted in three polarization sensitive pairs that were used for Galactic foreground studies. We present maps of the I,Q,U Stokes parameters over 17% of the sky and with a 13 arcmin resolution at 353 GHz (850 μm). They show a significant Galactic large scale polarized emission coherent on the longitude ranges [100°,120°] and [180°,200°] with a degree of polarization at the level of 4–5%, in agreement with expectations from starlight polarization measurements. Some regions in the Galactic plane (Gem OB1, Cassiopeia) show an even stronger degree of polarization in the range 10–20%. Those findings provide strong evidence for a powerful grain alignment mechanism throughout the interstellar medium and a coherent magnetic field coplanar to the Galactic plane. This magnetic field pervades even some dense clouds. Extrapolated to high Galactic latitude, these results indicate that interstellar dust polarized emission is the major foreground for PLANCK-HFI CMB polarization measurement.  相似文献   

9.
The primordial anisotropy polarization pathfinder array (PAPPA) is a balloon-based instrument to measure the polarization of the cosmic microwave background and search for the signal from gravity waves excited during an inflationary epoch in the early universe. PAPPA will survey a 20° × 20° patch at the North Celestial Pole using 32 pixels in 3 passbands centered at 89, 212, and 302 GHz. Each pixel uses MEMS switches in a superconducting microstrip transmission line to combine the phase modulation techniques used in radio astronomy with the sensitivity of transition-edge superconducting bolometers. Each switched circuit modulates the incident polarization on a single detector, allowing nearly instantaneous characterization of the Stokes I, Q, and U parameters. We describe the instrument design and status.  相似文献   

10.
Phase dependences of circular polarization were obtained with a precision Stokes polarimeter designed and constructed at the Main Astronomical Observatory of AS Ukraine. A study was made of dielectric and metallic powders with grains of diameter 10–100 m. Metallic powders were found to produce an essential circular polarization - up to 3%, just as dielectric powders did not show circular polarization values more than 0.05% Change of circular polarization with phase angle V is greatly depended on surface structure. Loose powders give phase curves with the same sign of circular polarization everywhere and with maximum at large phase angles V > 120 . Measurements of compacted powders show curves which change the sign repeatedly and have additional maxima, including a maximum at small phase angles V < 40 . A theory was created which considers a circular polarization as a result of multiple reflections of light from particulate surface. The theory provides reasonable good fit to the experimental data. It was concluded that measurements of circular polarization can be used to find metals in surface material of cosmic bodies (especially asteroids) and to determine characteristics of surface structure, in particular, to establish presence of regolith on metal-rich bodies.  相似文献   

11.
Polarization measurements of solar X-ray events that were obtained with an instrument on OSO-7 are presented. The results appear to be consistent with the results of Tindo et al. on the existence and magnitudes of polarization. A comparison with polarization predictions when X-rays are produced by radial beams of electrons gives two examples of deviations from such a model.  相似文献   

12.
In order to interpret the observed center to limb variations of spectrum and polarization of microwave impulsive bursts, gyro-synchrotron emission from nonthermal electrons trapped in a magnetic dipole field is computed. The theoretical spectrum and polarization are consistent with observed ones if we put an outer boundary of the radio source at a layer of 100-60 G or (7–9) × 104 km in height. Rather small observed center-limb variations in intensity and polarization are attributed to the distribution of , an angle between the magnetic field and the direction of observer, in the radio source emitting the burst, though the intensity and polarization depend strongly on especially at small values of .  相似文献   

13.
In a search for linear polarization effects, 37 profiles of the H line emitted in the 16 May 1991 flare have been analyzed. Linear polarization is clearly present in the central part of line. On average, the degree of polarization is 7 %, but it reaches 20 % in regions with lower H ga emission. Generally the orientation of the plane of polarization coincides with the flare to disk center direction, except for sections where the H ga line has the characteristic form observed in moustaches. We believe that the linear polarization observed in the 16 May 1991 flare was caused by bombardment of the chromosphere by beams of accelerated particles, protons in the main part of the flare and electrons at locations where the H ga line has the characteristic moustache structure.  相似文献   

14.
Interstellar polarization from aligned dust grains can be measured both in transmission at visible and near-infrared wavelengths and in emission at far-infrared and sub-mm wavelengths. These observations can help predict the behavior of foreground contamination of CMB polarimetry by dust in the Milky Way. Fractional polarization in emission from aligned dust grains will be at the higher range of currently observed values of 4–10%. Away from the galactic plane, fluctuations in Q and U will be dominated by fluctuations in intensity, and less influenced by fluctuations in fractional polarization and position angle.  相似文献   

15.
The impulsive phase of the 23 July 2002 2B/X4.8 proton flare with a classical two-ribbon structure was observed with the Irkutsk Large Solar Vacuum Telescope (LSVT) in spectropolarimetric mode, with high spatial, spectral, and time resolution. On the basis of 49 spectrograms and 1200 spectral cuts across the flare ribbons, evidence for Hα line impact polarization has been obtained. A systematic change of the Stokes Q and U parameters has been detected across the ribbons for different flare regions measured with a scanning step of 0.85″. In the eastern side of the ribbons, the degree of polarization is 4 – 8%; its plane is oriented toward the solar disk center (radial direction). In the western side, the polarization degree runs up to 25%, and its plane is perpendicular to the disk center direction (tangential direction). A comparison of these results with hard X-ray data (RHESSI) allows us to conclude that high-energy electron beams reached the chromosphere during this flare. The observed changes of the direction of polarization and the vanishing polarization within the ribbons mean that, at the chromospheric level, the energy of electrons remaining in the beam is about 200 eV. A shift of the peak position of polarization relative to the intensity maximum in the ribbons may result from the inclination of the electron beam axis with respect to the solar surface.  相似文献   

16.
The absorption features of ice at 3µm and of silicate at 10 and 20µm as well as the linear polarization across it have been calculated. The interpretations of data for protostellar objects BN and AFGL 2591 are made.The model of partially aligned spinning spheroidal grains with the Purcell's suprathermal alignment mechanism and the power law size distribution are considered. Core-mantle, porous and composite particles are investigated in the Rayleigh approximation. In the case of composite and porous grains the effective refractive indices are computed with the approximate Bruggeman rule.The influence of grain chemical composition, elongation and structure has been investigated. The distinctions in polarization between composite and core-mantle models are found. The mixing of grain materials smooths the individual spectral features of chemical components. The adding of graphite causes the shift of the 10µm peak position to shorter wavelengths. When the fraction of graphite increases, the peak at 20µm decreases and shifts to shorter wavelengths. The increase of elongation reduces the negative polarization at the 3µm feature, shifts the 10µm and 20µm peak positions to longer wavelengths, and raises the strength of the 20µm band. The porosity leads to similar effects.It was found that the studied grain models are in good agreement with observational data for BN and AFGL 2591 objects. The absence of polarization excess near 3µm for AFGL 2591 is attributable to a decrease in elongation of large grains as a result of coagulation. The attention is attracted to the problem of real distribution of the interstellar dust grains over the elongation parameter. The determination this distribution function and the study of its evolution in the processes of accretion and coagulation are necessary.  相似文献   

17.
This paper is devoted to a computation of the effect of a magnetic field on the linear polarization of the coronal L line of hydrogen. Recent works (Gabriel et al., 1971) have shown that the linear polarization of this line is due to resonant scattering of the incident chromospheric L line. The Hanle effect is the modification of this linear polarization, due to the magnetic field. After having briefly recalled the main features of this effect and the conditions of the coronal L line formation, we present the theoretical formalism to be used for Hanle effect computations. The effect of the hyperfine structure of the line is included. Then the results of our computations are given in terms of linear polarization as a function of the magnetic field. We get that the effect of the hyperfine structure on these results is negligible, although this is not evident a priori. When the hyperfine structure is neglected, the line structure is simplified and the Hanle effect can be expressed with analytical formulae, which we give in the last part of this paper. After integration along the line of sight, these formulae could be used for magnetic field determination in the solar corona from measurements of the linear polarization of the L line.  相似文献   

18.
Polarization measurements of type III bursts at 23.5 and 29.5 MHz have been compared for several years with indicators of magnetic fields in different height levels such as sunspot data, S-component characteristics, and noise storm data. By applying the Mount-Wilson and Brunner types of the related spot groups there results a positive relationship between the average degree of type III burst polarization and the magnitude or complexity of photospheric magnetic fields. For other parameters (leading spot area, peak intensity of the S-component at 9.1 cm wavelength) such a clear monotonic relation has not been found. Possibly the degree of polarization is influenced by height variations of the emitting level of the type III bursts at a fixed frequency due to variable electron densities. No connection has been detected between the type III burst polarization and noise storm fluxes which may be due to the local distance of the origin of both emissions.  相似文献   

19.
X-ray polarization measurements at three flares occurred in October 1969 were performed by means of a Thomson scattering type instrument installed on board the satellite Intercosmos-1. The polarization (P) at the wavelength of about 0,8 Å was detected at the rising phase and at the second maximum of intensity. The obtained averaged value of P for all three flares is 0.4 ± 0.2 at confidence level 0.9.  相似文献   

20.
We present the first ever simultaneous optical linear and circular polarization observations of blazars. These polarizations have been measured simultaneously inUBVRI-bands in three blazars; 3C 66A, OJ 287 and Markarian 421. Measured linear polarization in 3C 66A was the largest ever observed, at PR = 33.1 ± 0.5 per cent. In 3C 66A we detected small circular polarization in the other bands, exceptU. In OJ 287 we detected variable circular polarization in theU-band.  相似文献   

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