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1.
The BL Lac-type object 3C 66A was observed at the Crimean Astrophysical Observatory during the international project OJ-94. Observations were made over 10 nights from February through December 2003 at the Cassegrain focus of the 125-cm AZT-11 telescope with a photopolarimeter capable of simultaneous measurements in the UBVRI bands. In the course of our measurements the brightness of the object increased by more than 1 magnitude in all these bands. Its color indices varied and the degree of polarization decreased from ∼16% in February to ∼3% at the end of our observations. In December 2003 a rapid change in the position angle from 15° to 40° was noticed. The spectral energy distribution Fn is well described by a power law with a spectral index a (Fν ∝ ν −α . The increase in brightness was accompanied by a reduction in the spectral index. The most probable mechanism for the observed changes in the brightness, degree of polarization, and spectral index may be a decrease in the magnetic field strength or a change in its configuration owing to a increase in the chaotic component of the field. __________ Translated from Astrofizika, Vol. 49, No. 1, pp. 41–59 (February 2006).  相似文献   

2.
We presented the first polarimetric observations of five cataclysmic variables: MTDra, 1RXSJ184542.4+483134, CRTSCSS081231 J071126+440405, IPHASJ052832.69+283837.6, and CRTSCSS130604 J215427+155714. Observations in the V band have shown that all the objects are highly circularly polarized. All the objects except the last one change the polarization sign during the orbital period. The object 1RXSJ184542.4+483134 was observed in two brightness states in 2011 and 2012. The brightness decrease of the systemwas accompanied by the increase of the amplitude of circular polarization variation.  相似文献   

3.
Distributions of brightness and polarization,p, were obtained for the February 16, 1980 solar corona. Isophotes have a circular shape, typical for the period of the solar cycle maximum. A variety of structural features are distinctly seen in the distribution ofp. The polarization reaches 55%, and thep values are comparatively high, not only in the well-defined streamers, but in the overlapping faint rays and small streamers, as well. A theoretical interpretation of the observed high degrees of polarization, taking into account the data on coronal brightness, is very difficult. This cannot be done within the scope of spherically symmetric models of the corona; the assumption of a high concentration of coronal matter into the plane of the sky is needed. With the most extreme densities in coronal structures, it is not, however, possible to exceed the observed valuep = 55%. Taking into account the accuracy of the polarization measurements, there are no reasons to reject the Thomson scattering as a basic mechanism to explain the origin of the white-light corona.  相似文献   

4.
S. Ganesh 《Icarus》2009,201(2):666-673
Comet NEAT C/2001 Q4 was observed for linear polarization using the optical polarimeter mounted at the 1.2 m telescope at Mt. Abu Observatory, during the months of May and June 2004. Observations were conducted through the International Halley Watch narrow band (continuum) and BVR broad band filters. During the observing run the phase angle ranged from 85.6° in May to 55° in June. As expected, polarization increases with wavelength in this phase angle range. Polarization colour in the narrow bands changes at different epochs, perhaps related to cometary activity or molecular emission contamination. The polarization was also measured in the cometary coma at different locations along a line, in the direction of the tail. As expected, we notice minor decrease in the polarization as photocenter (nucleus) is traversed while brightness decreases sharply away from it. Based on these polarization observations we infer that the Comet NEAT C/2001 Q4 has high polarization and a typical grain composition—mixture of silicates and organics.  相似文献   

5.
We present new polarimetric and photometric observations of the high-albedo Asteroid 64 Angelina in the UBVRI wavebands at phase angles ranging from 0.43° to 13.02° during oppositions in 1995, 1999, and 2000/2001. The polarization opposition effect has been observed in the form of a sharp peak of negative polarization with amplitude of about −0.4% centered at αmin≈1.8°, which is superimposed on the regular negative polarization branch. The amplitude of the polarization opposition effect appears to be apparition-dependent. Our photometric data confirm the early detected by Harris et al. [1989. Phase relations of high-albedo asteroids: The unusual opposition brightening of 44 Nysa and 64 Angelina. Icarus 81, 365-374] of a very strong and unusually narrow opposition spike, i.e., brightness opposition effect, for Angelina. Thus, 64 Angelina is the first asteroid for which both the polarization opposition effect and the brightness opposition effect have been detected. We observed that the polarization opposition effect as well as the regular negative polarization branch depends on the wavelength of scattered light, but in different manners. In addition, the colors B-V and V-R show little phase-angle dependence, while the color U-B increases with increasing phase angle, thus indicating that the amplitude of the brightness opposition effect is larger in the U band and almost the same in the B, V, and R bands. It appears that all colors indices begin to increase with decreasing phase angle to zero. The composite lightcurve computed with a period of 8.752 h has amplitude of 0.13 magnitude.  相似文献   

6.
The results of polarimetric observations of long-period Mira variables obtained over the past 30 years at the Byurakan observatory are presented. Analysis of these observations shows that there is a real correlation between the degree of light polarization and the brightness of these stars. The maximum degree of polarization is observed at the middle of the ascending branch of the light curve. The degree of polarization is correlated with the period of brightness variation. The average degree of polarization of Mira stars increases with an increase in their period up toP=380 days.Translated fromAstrofizika, Vol. 39, No. 4, pp. 541–551, November, 1996.  相似文献   

7.
The results of photometric and polarimetric observations of the star CH Cygni in the B, V, and R filters are presented. Variations of brightness and color indices are given as functions of the time of observation. A fairly irregular character was found, both in the brightness variations and in the variations of color indices. The polarization observations showed that the light of CH Cygni is intrinsically polarized.  相似文献   

8.
In this paper, we derived the empirical relationship between stellar surface brightness parameter (F v) and (V —R c) colour in Cousins system appropriate to dwarf cepheids. Also theoretical counterpart to this relation has been calculated from model atmospheres. The theoretical relation is in reasonable agreement with the empirical relation but reveals small sensitivities to surface gravity and metallicity. Both relations were used to apply the surface brightness method to estimate the radius of four dwarf cepheids of YZ Boo, AD CMi, XX Cyg, and EH Lib which were observed withV andR band in Cousins photometric system by Kim and Joner (1994). We could obtain the reliable result for AD CMi and it was found that, for three other variables, there are large phase shifts between angular diameter variation and radial displacements.  相似文献   

9.
Bohlin  J. D.  Garrison  L. M. 《Solar physics》1974,38(1):165-179
A general computer program has been developed to numerically integrate the Thomson scattered light from arbitrary inhomogeneous models of the solar corona. Conversion from the observer's to solar coordinates is totally general to eliminate restrictions on the lines-of-sight that may be investigated. The tangential and radial components (K t and K r ),or any combination thereof, are calculated. Four separate output modes are available, corresponding to the common formats used for coronal brightness and polarization data.This program was used to investigate the major NW streamer of the 1972 eclipse. The bifurcated profile of this feature is reproduced by the projection effect of a radially expanding blade, or fan, whose longitudinal axis is twisted to follow an underlying magnetic neutral line on the solar surface. Thus a purely geometrical effect accounts for the observed intensity profile. Published brightness data for the NE streamer of the 1970 eclipse are also reinterpreted using the radially-expanding fan model. The axial density gradients of 1970 and 1972 features are found to be virtually identical from 3 to 8 R .  相似文献   

10.
Conclusions  From the results of our observations, we can say the following: the polarization decreased and the brightness increased during the observations (Fig. 1). There is no definite relationship between the polarization parameters (P, θ ) and wavelength λ (U, B, V, R). The authors wish to thank L. G. Akhverdian for providing the photograph in Fig. 2. Translated from Astrofizika, Vol. 41, No. 2, pp. 311–315, April-June, 1998.  相似文献   

11.
We present the results of the blazar 3C 345 monitoring in Johnson‐Cousins BVRI bands for the period 1996–2006. We have collected 29 V and 43 R data points for this period; the BI light curves contain a few measurements only. The accuracy of our photometry is not better than 0.03 mag in the VR bands. The total amplitude of the variability obtained from our data is 2.06 mag in the V and 2.25 mag in the R band. 3C 345 showed periods of flaring activity during 1998/99 and 2001: a maximum of the blazar brightness was detected in 2001 February – 15.345 mag in the V and 14.944 mag in the R band. We confirm that during brighter stages 3C 345 becomes redder; for higher fluxes the colour index seems to be less dependent on the magnitude. The intra‐night monitoring of 3C 345 in three consecutive nights in 2001 August revealed no significant intra‐night variability; 3C 345 did not show evident flux changes over timescales of weeks around the period of the intra‐night monitoring. This result supports the existing facts that intra‐night variability is correlated with rapid flux changes rather than with specific flux levels. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

12.
Vardanyan  R. A. 《Astrophysics》1994,37(2):138-142
Based on analysis of photometric, colorimetric, and polarimetric data, we show that red variable stars of high luminosity are divided with respect to their period of brightness variation into two groups: I) binary stars with periods larger than 480 days; II) single stars with periods less than 480 days. The binary stars exhibit: a) large correlation coefficients between the V-band brightness variation and the U-B, B-V colors; b) comparatively smaller U-B colors (< 1. m 5);c)strong variability of polarization parameters. Based on this division, we suspect that the star PZ Cas is a binary.Translated from Astrofizika, Vol. 37, No. 2, pp. 235–244, April–June, 1994.In conclusion, the author wishes to express deep gratitude to professor L. V. Mirzoyan for valuable comments.  相似文献   

13.
Guangli Huang 《Solar physics》2006,237(1):173-183
Based on the approximations of the non-thermal gyro-synchrotron radiation used by G.A. Dulk, and K.A. Marsh, Astrophs. J. 259, 350, 1982, the author analyses calculations of the propagation angle and coronal magnetic field self-consistently with brightness temperature, spectral index, frequency, turnover frequency, and polarization degree in solar microwave bursts. Hence, the coronal magnetic fields parallel and perpendicular to the line-of-sight in the sources of microwave bursts are calculated theoretically, and discussed in an event observed by the Nobeyama Radio Polarimeters (NoRP).  相似文献   

14.
Results of photoelectric BV observations of the brightness and polarization in the V band for S Per and T Per over a period of eight years are presented. An attempt is made to isolate the interstellar polarization. A comparison of the variations in the brightness and intrinsic polarization reveals some relationships among these quantities.  相似文献   

15.
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   

16.
The water ice and silicate dust bands centered at about 3 and 10 μm, respectively, are simultaneously observed in the spectra of several objects. So far the wavelength dependence of the polarization in both bands has been modeled using two-layer spheroids, with the shape of the silicate core being confocal to that of the ice mantle. We show that nonconfocality of the spheroidal core and mantle boundaries changes fundamentally the wavelength dependence of the polarization within the 10-μm silicate band and affects significantly the polarization within the 3-μm water ice band, while the extinction profiles of these bands remain essentially unchanged. Since the results have been obtained for a theoretical model, we discuss their applicability and significance for cosmic dust grains. Original Russian Text ? M.S. Prokopjeva, V.B. Il’in, 2007, published in Pis’ma v Astronomicheskiĭ Zhurnal, 2007, Vol. 33, No. 10, pp. 784–791.  相似文献   

17.
UBV measurements of the light of the night sky in the auroral zone during three seasons are presented. The mean brightness of the night sky in theV band is found to be equal one 18m1 star (arc sec)–2, with considerable variations. The observed meanB-V andU-B indicies are +0 . m 7 and –1 . m 6, respectively.Light curves of variable stars during strong auroral activities are also shown. On the basis of measurements we briefly discuss the possibility of accurate stellar photometry in the auroral region.  相似文献   

18.
D. B. Melrose 《Solar physics》1989,120(2):369-381
There is a characteristic maximum brightness temperature T B 1015K for type III solar radio bursts in the solar wind. The suggestion is explored that the maximum observed values of T Bmay be attributed to saturation of the processes involved in the plasma emission. The processes leading to fundamental and second harmonic emission saturate when T Bis approximately equal to the effective temperature T Lof the Langmuir waves. The expected maximum value of T Bis estimated for this saturation model in two ways: from the growth rate for the beam instability, and from the maximum amplitude of the observed Langmuir turbulence. The agreement with the observed values is satisfactory in view of the uncertainties in the estimates (a) of the intrinsic brightness temperature from the observed brightness temperature, (b) of the actual growth rate of the beam instability, which must be driven by local, transient features (that are unobservable using available instruments) in the electron distribution, and (c) in the k-space volume filled by the Langmuir waves, and this is consistent with the observational data on two well-studied events at the orbit of the Earth and with statistical data for events over a range of radial distances from the Sun.  相似文献   

19.
A study of the background corona near solar minimum   总被引：2，自引：0，他引：2  
The white light coronagraph data from Skylab is used to investigate the equatorial and polarK andF coronal components during the declining phase of the solar cycle near solar minimum. Measurements of coronal brightness and polarization brightness product between 2.5 and 5.5R during the period of observation (May 1973 to February 1974) lead to the conclusions that: (1) the equatorial corona is dominated by either streamers or coronal holes seen in projections on the limb approximately 50% and 30% of the time, respectively; (2) despite the domination by streamers and holes, two periods of time were found which were free from the influences of streamers or holes (neither streamers nor holes were within 30° in longitude of the limb); (3) the derived equatorial background density model is less than 15% below the minimum equatorial models of Newkirk (1967) and Saito (1970); (4) a spherically symmetric density model for equatorial coronal holes yields densities one half those of the background density model; and (5) the inferred brightness of theF-corona is constant to within ±10% and ±5% for the equatorial and polar values, respectively, over the observation period. While theF-corona is symmetric at 2R it begins to show increasing asymmetry beyond this radius such that at 5R the equatorialF-coronal brightness is 25% greater than the polar brightness.The National Center for Atmospheric Research is sponsored by the National Science Foundation.  相似文献   

20.
Results of photoelectric observations in the Strömgren system of the Herbig Ae/Be star LkH 215 are presented. It is found that this star undergoes bursts. Two types of bursts are observed. The amplitude of the first type of burst increases with decreasing wavelength. In the second type of burst, the brightness amplitude has a maximum in the V band.  相似文献   

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