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MAIN SCIENTIFIC RESULTS |
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1. Speckle interferometry of stars.
The speckle interferometric technique provides a possibility to reach a resolution limited only by the diffraction at a telescope aperture. To achieve this, a special statistical processing of a set of short-exposure (0.02 s or less) frames is to be fulfilled which would allow to obtain the estimate of an object's power spectrum or autocorrelation function. In 1997-81, speckle interferometry of red giants and close binaries was fulfilled with the 6-meter BTA telescope using an image tube and a photographic film as a detector. Angular diameters of Arcturus (0.018 arsec), Betelgeuse (0,042 arcsec) and Aldebaran (0.026 arcsec) were measured with an accuracy of 10% [5, 17], and angular separations for 28 close binary stars were determined, with an accuracy of 0.001-0.003 arcsec [7,11]. In the 80-ths, speckle interferometry of broad stellar pairs from the young stellar system in Orion Trapezium was fulfilled at the Abastumani 1.25-m telescope with aim to detect the mutual motions of stars populating the cluster, [13]. To process the speckle series, usually consisting of 100-200 short-exposure photographic frames, a coherent optical processor of Kharkov University was used, [4].
2. Speckle interferometry of asteroid 4 Vesta.
The observations of asteroid 4 Vesta was made in opposition of 1988 with the Maidanak 1-m telescope using an image tube and a photographic film as a detector, [16,20]. Both the analogous [16] and digital [20] tecniques for statistical processing of Vesta's speckle series have been applied. The estimates of the major and minor axes of Vesta's projected disc have been obtained for three epochs, [16], and specific errors of the speckle interferometric technique have been analysed. In addition, a special algorithm was proposed, [14,20], which turned out to be very efficient in solving the well known "phase problem" in optics thus allowing to synthesize the diffraction-limited images from speckle interferometric data.
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The image of asteroid 4 Vesta synthesized with the diffraction-limited resolution of the 1-m telescope (0.11 arcsec) from a speckle series consisting of 300 short-exposure photographic frames,[20]. Some albedo features can be seen at the disk for which the major axis of 0.482 arcsec had been measured with an accuracy of 0.014 arcsec. The existence of similar features was confirmed by the HST data later. |
3. Ground-based support of space missions.
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The images of Mars in the opposition of 1992, 1-meter telescope, Maidanak Mountain, speckle camera of AO KhU, [12]. The initial series of short-exposure (5 ms) images in blue, green and red wavelengths were taken by sets consisting of about 100 frames in each filter. After image processing with a special algorithm, a colour image of Mars has been synthesized. The features as small as 0.4 arcsec can be seen at the disk which was of 14 arcsec in diameter at this time, [17]. The observations have been fulfilled in the framework of a ground-based optical support of space missions to the red planet. |
4. Observations of Shoemaker-Levy 9 -Jupiter collision
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High-resolution
imaging and polarimetry of Jupiter during the Comet Shoemaker-Levy
9 impact have been made in visual wavelengths with the 1.5-m and
1-m telescopes at the Maidanak Observatory, [19]. Characteristic
altitudes of debris clouds over Jovian ammonia clouds were estimated
to be about 1000km from a pair of images separated by a 40-min time
interval. The increased values of a degree of polarization at the
impact sites as compared to the adjacent undisturbed regions were
also noted, - up to 2% higher than for the surroundings.
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5. High-resolution imaging and photomertry of gravitational lens sytems (GLS)
Gravitational lensing phenomenon is now regarded to be an important clue to solving a set of fundamental astrophysical problems, from examining the physical properties of the most distant astronomical objects to determining the overall geometry of the Universe. The most powerful source of our knowledge about the GLS are observations aimed at obtaining the high-precise and well-sampled lightcurves of individual gravitationally split quasar images in various wavelengths.
Investigation of selected gravitational lens systems is being caried out in cooperation with the Institute of Radio Astronomy of Nat.Ac.Sci. of Ukraine (Kharkov), Sternberg State Astronomical Institute (Moscow), and Ulug-Bek Astronomical Institute of Nat.Ac.Sci. of Uzbekistan, (Tashkent), and with the kind support and assistance from the Maidanak Foundation, http://www.maidanak.org, CRDF Cooperative Grant Program, award number UP2-302, with Prof. B.Paczynski as a U.S. coordinator, bp@astro.princeton.edu, Prof. S.Refsdal from the Astronomical Observatory, University of Hamburg, st2f101@hs.uni-hamburg.de, and Prof. R.Schild from the Harvard University.
5.1 Q2237+0305
This extremely compact object consists of four gravitationally split quasar images arranged almost symmetrically around the nucleus of a barred Sb galaxy within a circle of less than 2arsec in diameter. Because of the complexity of its structure, strengthened by a very steep and substantial light contribution of the nuclear region of the galaxy, there are great difficulties in observing the object, as well as in making good photometry for the components. Extremely good seeing conditions and special algorithms of photometric image precessing are needed to obtain the reliable brightness estimates of the quasar components.
Noticeable brightness and colour variations of the individual quasar components are being permanently observed in the Q2237+0305 system since the first observations in 1987. Monitoring of transient phenomena in the Q2237+0305 gravitational lens system (the Einstein Cross) with the Maidanak 1.5-m telescope are being regularly carried out since 1995, [ 21, 22]. More than 30 dates have neen added to the existing brightness variations database which permitted to trace the photometric behavior of the components up to 1999.
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Q2237+0305 at three different epochs, from left to right: Sept. 17, 1995, Aug. 30, 1997, and Aug 30, 1998, R filter. The picture demonstrates noticeable mutual brightness variations of the quasar components.
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Click to see advanced picture. A prominent brightening of the component C which started in September 1997 and lasted till at least August 1998 when the component C became approximately 0.4 mag brighter than B is the most interesting event in the system at this time period. A noticeable systematic decrease in brightness of the component A should be also mentioned, as well as slight fading of the B component.
The next picture demonstrates long term brightnes variations of Q2237+0305 components measured since the system discovery in 1987. Blue marks denote observations of the DIP staff.
In addition to variations of mutual brightness of the quasar components, noticeable change of their colour was observed in the system, - the component C, which was the most red one in the pioneering observations of 1987, is now the most blue component in the system. No unambiguous explanation of this phenomenon exists at present.
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Simulation
of the microlensing phenomenon.Click to see the animated picture.
5.2 H1413+117
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H1413+117 |
The H1413+117 (Clover Leaf), an extremely compact GL system. No lensing galaxy is found and no microlensing events have been reported. The CCD images were taken with the1.5 meter AZT-22 telescope at Maidanak Mountain in July 1997 under rather poor seeing conditions. To the left: the sum of four initial 2-min exposure frames. To the right: the left image restored with the Richardson-Lucy algorithm (200 iterations). The characters denote four Clover Leaf components. |
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5.3 Other Gravitational lenses |
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PG-1115 |
SBS-1520 |
B-1422 |
RXJ-0911 |
