Alexander P. Zheleznyak

Alexander P. Zheleznyak
V. N. Karazin Kharkiv National University · Institute of Astronomy

PhD

About

38
Publications
1,454
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225
Citations

Publications

Publications (38)
Article
Full-text available
Quasar microlensing offers a unique opportunity to resolve tiny sources in distant active galactic nuclei and study compact object populations in lensing galaxies. We therefore searched for microlensing-induced variability of the gravitationally lensed quasar QSO 2237+0305 (Einstein Cross) using 4374 optical frames taken with the 2.0 m Liverpool Te...
Preprint
Full-text available
Quasar microlensing offers a unique opportunity to resolve tiny sources in distant active galactic nuclei and study compact object populations in lensing galaxies. We therefore searched for microlensing-induced variability of the gravitationally lensed quasar QSO 2237+0305 (Einstein Cross) using 4374 optical frames taken with the 2.0 m Liverpool Te...
Article
Full-text available
We report the results of an optical spectroscopic follow-up of four double quasar candidates in the Sloan Digital Sky Survey (SDSS) database. SDSS J1617+3827 is most likely a lensed quasar at z = 2.079, consisting of two images with r ∼ 19−21 and separated by ∆θ ∼ 2. We identify an extended source northeast of the brightest image as an early-type l...
Preprint
Full-text available
We report the results of an optical spectroscopic follow-up of four double quasar candidates in the Sloan Digital Sky Survey (SDSS) database. SDSS J1617+3827 is most likely a lensed quasar at z = 2.079, consisting of two images with r ~ 19-21 and separated by ~ 2 arcsec. We identify an extended source northeast of the brightest image as an early-ty...
Article
Full-text available
The optical spectroscopic follow-up of SDSS-III selected targets (Sergeyev et al. 2016MNRAS.456.1948S) has led to the discovery of the double quasar SDSS J1617+3827AB at redshift z = 2.079.
Article
We present new photometric observations of H1413+117 acquired during seasons between 2001 and 2008 in order to estimate the time delays between the lensed QSO images and to characterize at best the on-going micro-lensing events. We propose a highly performing photometric method called the adaptive PSF fitting and have successfully tested this metho...
Article
Full-text available
Optically bright, wide separation double (gravitationally lensed) quasars can be easily monitored, leading to light curves of great importance in determining the Hubble constant and other cosmological parameters, as well as the structure of active nuclei and haloes of galaxies. Searching for new double quasars in the Sloan Digital Sky Survey III (S...
Article
Full-text available
The AZT-22 telescope, equipped with the ML09000-65 CCD camera, has shown to be capable of obtaining high-quality images of astronomical objects and thus solving a wide range of observational tasks. Diffraction-limited telescope optics together with the excellent seeing conditions at Mt. Maidanak Observatory allows recording images with the seeing q...
Article
We report the results of our multicolour observations of PG 1115+080 with the 1.5-m telescope of the Maidanak Observatory (Uzbekistan, Central Asia) in 2001–2006. Monitoring data in filter R spanning the 2004, 2005 and 2006 seasons (76 data points) demonstrate distinct brightness variations of the source quasar with the total amplitude of almost 0....
Article
Full-text available
We present and analyse new R-band frames of the gravitationally lensed double quasar FBQ 0951+2635. These images were obtained with the 1.5-m AZT-22 Telescope at Maidanak (Uzbekistan) during the 2001–2006 period. Previous results in the R band (1999–2001 period) and the new data allow us to discuss the dominant kind of microlensing variability in F...
Article
Full-text available
An observing campaign with 10 participating observatories has undertaken to monitor the optical brightness of the Q0957 gravitationally lensed quasar for 10 consecutive nights in 2000 January. The resulting A image brightness curve has significant brightness fluctuations and makes a photometric prediction for the B image light curve for a second ca...
Article
Full-text available
To go into the details about the variability of the double quasar SBS 0909+532, we designed a monitoring programme with the 2 m Liverpool Robotic Telescope in the r Sloan filter, spanning 1.5 years from 2005 January to 2006 June. The r-band light curves of the A and B components, several cross-correlation techniques and a large number of simulation...
Article
Full-text available
The time delays between the components of a lensed quasar are basic tools to analyze the expansion of the Universe and the structure of the main lens galaxy halo. In this paper, we focus on the variability and time delay of the double system SBS 0909+532A,B as well as the time behaviour of the field stars. We use VR optical observations of SBS 0909...
Article
Full-text available
We present the R c-band light curves for components A and B of the gravitationally lensed quasar SBS 1520+530 obtained during 2001–2005 with the 1.5-m Russian-Turkish Telescope (RTT-150) at the TUBITAK National Observatory (Turkey). Based on an analysis of the data for the period 2001–2002, we have estimated the time delay of the brightness fluctua...
Article
Spatially resolved CCD photometry of the Q2237+0305 gravitationally lensed quasar in V, R and I spectral bands from observations with the Maidanak 1.5-m telescope made in 1995-2000 is presented. For each of the four quasar components, - A, B, C and D, - stellar magnitudes for 78 dates in R filter, and for 17 dates in V and I and shown in Tables 4-6...
Article
Full-text available
Photometry of the Q2237+0305gravitational lens in VRI spectral bands with the 1.5-m telescope of the high-altitude Maidanak observatory in 1995-2000 is presented. Monitoring of Q2237+0305 in July-October 2000, made at nearly daily basis, did not reveal rapid (night-to-night and intranight) variations of brightness of the components during this time...
Article
Observations of the gravitationally lensed quasar SBS 1520+530 obtained in 2000–2001 on the 1.5-m telescope of the Ma $$\overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\smile}$}}{l} $$ danak Observatory (Uzbekistan) are presented. The photometric algorithms used to observe the components of SBS 1520+530 are discussed. The images have a resolu...
Article
Full-text available
We obtained a series of more than two hundred R-band CCD images for the crowded central (115″×77″) region of the metal-poor globular cluster M 15 with an angular resolution of 0\mathop ." 5 - 0\mathop ." 90\mathop .\limits^{''} 5 - 0\mathop .\limits^{''} 9 in most images. Optimal image subtraction was used to identify variable stars. Brightness v...
Article
Full-text available
We report on an observing campaign in March 2001 to monitor the brightness of the later arriving Q0957+561 B image in order to compare with the previously published brightness observations of the (first arriving) A image. The 12 participating observatories provided 3543 image frames which we have analyzed for brightness fluctuations. From our class...
Article
Full-text available
Since 1997, a program of observations of gravitational lens systems (GLS) with the 1.5-m telescope of the high-altitude Maidanak Observatory has been carried out by joint efforts of seven institutions from five countries. The Q2237+0305, Q0957+561, SBS 1520+530, and other GLS were observed in VRI spectral bands using the TI 800×800, Pictor 416 and...
Article
The results of two-year observations of the known Q2237+0305 gravitational lens system (Einstein Cross) with the Maidanak 1.5-meter telescope are presented. A contribution of these observations to the existing R lightcurves of four quasar components consists of 12 dates during 133 days in 1997, and of 15 dates during 115 days in 1998. Three-colour...
Article
The brightness of four components of the gravitational lens system QSO 2237+0305 was measured in the R band, made from 2 Jul - 14 Nov 1997. The image processing algorithm is described, and possible sources of errors are discussed. Brightness variations are observed. Based on a very simple microlensing model, the authors estimate a typical mass of t...
Article
The brightness of four components of the gravitational lens system QSO 2237+0305 was measured in the R band, made from 2 Jul - 14 Nov 1997. The image processing algorithm is described, and possible sources of errors are discussed. Brightness variations are observed. Based on a very simple microlensing model, the authors estimate a typical mass of t...
Article
The peculiar T Tauri type star V1331 Cyg = LkH 120, located in the dark cloud Lynds 984, is a FU Orionis pre-outburst candidate (McMuldroch et al. , 1993). This star embedded in circumstellar bright nebulosity is also surrounded by a helix-shaped nebula originated from the star. We obtained a series of speckle images of V1331 Cyg on the standard VB...
Article
Preliminary results of imaging of the unusual T Tauri star V1331 Cyg and its environment made in the frame of our multiobject programme for the study of nebulae, outflows and jets from young stars and related objects are presented. The fine structure of the nebula was determined and its parameters were evaluated. The evidence for optical outflows w...
Article
Full-text available
Observations of the gravitationally lensed quasar Q2237+0305 were made with the 1.5-meter AZT-22 telescope at Maidanak (Uzbekistan) on 17-19 September 1995. All four components of the quasar are clearly resolved. The results of photometric measurements of the components are presented. It is confirmed that the component A again became the brightest...
Article
The peculiar T Tauri type star V1331 Cyg = LkH 120, located in the dark cloud Lynds 984, is known as the FU Orionis pre-outburst candidate (McMuldroch et al., 1993). This star embedded in circumstellar bright nebulosity is also surrounded by helix-shaped nebula originated from the star. We obtained the series of speckle images of V1331 Cyg in stand...
Article
We present the results of the observations of the comet/P Shoemaker-Levy 9 impact on Jupiter at Maydanak Observatory (Uzbekistan) with excellent seeing conditions (see ,e.g., W. B. Scott Aviation Week & Space Technology,1995, v.142, N20, p.68).The photographic, polarimetric and speckle imaging observations of Jupiter were carried out on the 1.5m (A...
Article
A fast microphotometer with one-dimensional CCD for fast photometry of photographic images is described. Optical and electric schemes are discussed. Main phototechnical characteristics are presented. The results of processing Mars composite images in B, V, R passbands demonstrate the device possibilities.
Article
A review is given of main results on the problem of angular resolution increase for ground-based observations obtained at the Kharkov Astronomical Observatory since 1980. The general conception of solving this problem is formulated on the basis of the authors' original works. Several specific examples of image processing are presented including spe...
Article
Speckle interferometric data for Vesta and diffraction-limited images of Vesta's disk are presented for three measurements near the opposition of 1988. It is argued that polarimetric data can be utilized to estimate a contribution of albedo features to Vesta's lightcurve, and thus to derive the geometric component of the lightcurve. The analysis of...
Article
The speckle camera based on the image intentifier YM-92 is described. It is applied for observations of binary stars. The field of view is 30arcsec, limiting stellar magnitude is 6m. The possibility of a high-precision speckle interferometric measurements of binary stars with separations up to 30arcsec is demonstrated.
Article
Basic observational data on two SX Phe stars, isolated for the first time in the innermost region of the globular cluster M15, are presented.

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Project (1)
Project
Gravitational lensing is a unique astrophysical tool to investigate the dark side of the Universe, since analyses of multiple quasars (which have undergone a gravitational lens effect) reveal the structure and composition of tiny regions in distant active galactic nuclei, halos of lensing galaxies and the intergalactic space. Thus, in the framework of the Gravitational LENses and DArk MAtter (GLENDAMA) project, we are building a publicly-available online database for a sample of ten bright gravitationally lensed quasars (GLQs) in the northern hemisphere (see http://grupos.unican.es/glendama). Although we used many telescopes and a varied instrumentation throughout the past 20 years, the Liverpool Telescope (LT) and the Gran Telescopio CANARIAS (GTC) played a key role, and we will continue using the LT & GTC in the next decade. Our long-term observing programme with the LT is a singular and legacy initiative, which offers a unique opportunity to complete a detailed monitoring of each GLQ over 10-30 years. These timescales are crucial to, among other things, detect significant microlensing effects in practically all objects in the sample and accurately measure 10-12 time delays between quasar images. In addition to optical light curves, the LT & GTC allows us to follow-up the spectroscopic activity of GLQs.