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Information × Registration Number 0204U003180, 0101U002777 , R & D reports Title Observations of gravitational lensed quazars popup.stage_title Head Dudinov V., Registration Date 16-02-2004 Organization Kharkov National University named after V.N.Karazin popup.description2 Object of investigation: gravitational lensing phenomenon, in particular, gravitationally lensed quasars, with their mul;tipple images formed by gravitational fields of foreground galaxies in the case when they are located near the sightline between the quasar and the observer. Objective: measurement of stellar magnitudes and color indices of individual lensed quasar components as function of time, and their use to study the quasar spatial structure and the properties of stellar and substellar population of lensing galaxies; studying the extinction laws in the dark matter of other galaxies. Technique of the investigation: CCD photometry with the use of various algorithms of image porocessing such as double iterative PSF subtraction, optimal PSF subtraction, etc.; speckle interferometry, correlation analysis of the sparce and uneven datasets; computer simulation of various effects of gravitational lensing. Results of long-term observations of Q2237+0305, SBS 1520+530 and Q0957+561 gravitational lenses are presented, made in 1995-2000 and the 1.5-m AZT-22 telescope on Maidanak mountain (Central Asia), which is known to the excellent seeing conditions. For Q2237+0305 system, R lightcurves of the four lensed quasar components were built, which involve the time period from 1997 to 2000. The most dramatic brightness changes were observed for the C component, which became 1m brighter and faded again during three years. The detailed light curves of Q2237+0305 are also presented, built on the basis of almost daily observations during three months in 2000 which do not reveal night-to-night brightness variations within the error bars but demonstrate rather noticeable trends at the time scale of one-two months. The photometry accuracy is 0.01m-0.02m for the brighter A and B components and 0.05m-0.07m for the fainter C and D ones. A behavior of color indices of the components is discussed derived from the results of photometry in V, R and I spectral bands. In particular, a statistical analysis revealed the tendency of the components to become bluer as their brightness increases. The most prominent color change that accompanies the microlensing event of the C component with the maximum in 1999 is 0.43m at the (V-I) base. Plausible reasons for the discovered tendency are discussed: 1) microlensing of a source that has larger effective size in the red spectral region as compared to that shorter wavelengths; and also 2) color changes are caused by variable extinction in the dark matter of the lensing galaxy. For the SBS 1520+530 system the new, more accurate estimates of R and I magnitudes of the lensing galaxy were obtained, with the R magnitude being estimated for the first time. In monitoring of 2000 variations of brightness of the lensed components were observed which somewhat exceeded the errors of photometry and are of 0.04m at the time scales of weeks to months. Observations of 1998-2001 demonstrate larger brightness variations of A and B components with the maximal amplitudes of 0.2m and 0.25m respectively, at the time scales of months. Numerical simulation allowed to estimate the mass of the lensing galaxy and the parameter thar determines the mass distribution which are consistent with the system geometry and the relative amplification factor observed. The mass estimate as well as the obtained (H-R) color index indicates that the SBS 1520_530 lensing galaxy is spiral. Observations of Q0957+561 gravitational lens were carried out in the framework of the international monitoring program "QuOC Round-the-clock" launched by Prof. R.Schild (Center for Astrophysics, Harvard, USA) with the aim to obtain more accurate estimate of the time delay between the quasar brightness variations seen in the lensed A and B quasar images. This quantity is needed to obtain the new estimate of the Hubble constant. The results of this monitoring, as well as numerous observations of the previous years, reveal rapid variations of brightness which can be explained by microlensing of the quasar by the bodies with substellar or planetery masses in the case when compact features are present in the quasar structure. Computer simulation of the Q0957+561 light curves with the new double ring quasar structure model has been carried out which demonstrated good agreement of the simulated light curves with those that are observed. Speckle interferometric observations of close binary star systems with the late spectral class components were carried out at the 6-m BTA telescope. 312 measurements of positional parameters and 231 estimates of magnitude difference for 124 binaries and multiple systems have been made on the basis of 800 speckle interferometric datasets obtained. A new binary system and 5 triple stellar systems have been discovered. 15 new orbits have been built and 5 previously known orbits have been specified. Absolute stellar magnitudes and spectral classes of the components of 68 binary and 4 triple systems have been obtained. The results of the work is of potential interest in such fields of the fundamental science as galactic and extragalactic astronomy and cosmology. Investigation of gravitationally lensed quasars were being carried out in collaboration with the Institute of Radio Astronomy of Nat.Ac.Sci. of Ukraine in the framework of the proper Agreement. In April 2002 the Agreement between the Nat.Ac.Sci. of Ukraine and the Ac.Sci. of Republicof Uzbekistan "On development and the joint use of the observational base on Maidanak Mountain in scientific research" was ratified. In the end of 2000 the agreement about the scientific collaboration with the Harvard-Smithsonian Center of Astrophysics (USA) in investigation of gravitaional lensing phenomenon was concluded. Product Description popup.authors popup.nrat_date 2020-04-02 Close