Gaia and VLT astrometry of faint stars: Precision of Gaia DR1 positions and updated VLT parallaxes of ultracool dwarfs

We compared positions of the Gaia first data release (DR1) secondary data set at its faint limit with CCD positions of stars in 20 fields observed with the VLT/FORS2 camera. The FORS2 position uncertainties are smaller than one milli-arcsecond (mas) and allowed us to perform an independent verification of the DR1 astrometric precision. In the fields that we observed with FORS2, we projected the Gaia DR1 positions into the CCD plane, performed a polynomial fit between the two sets of matching stars, and carried out statistical analyses of the residuals in positions. The residual RMS roughly matches the expectations given by the Gaia DR1 uncertainties, where we identified three regimes in terms of Gaia DR1 precision: for G = 17-20 stars we found that the formal DR1 position uncertainties of stars with DR1 precisions in the range of 0.5-5 mas are underestimated by 63 +/- 5\%, whereas the DR1 uncertainties of stars in the range 7-10 mas are overestimated by a factor of two. For the best-measured and generally brighter G = 16-18 stars with DR1 positional uncertainties of <0.5 mas, we detected 0.44 +/- 0.13 mas excess noise in the residual RMS, whose origin can be in both FORS2 and Gaia DR1. By adopting Gaia DR1 as the absolute reference frame we refined the pixel scale determination of FORS2, leading to minor updates to the parallaxes of 20 ultracool dwarfs that we published previously. We also updated the FORS2 absolute parallax of the Luhman 16 binary brown dwarf system to 501.42 +/- 0.11 masComment: 7 pages, 4 figures, 2 tables, accepted for publication in A&A on August 1, 201

Astrometric search for a planet around VB 10

We observed VB 10 in August and September 2009 using the FORS2 camera of the VLT with the aim of measuring its astrometric motion and of probing the presence of the announced planet VB 10b. We used the published STEPS astrometric positions of VB 10 over a time-span of 9 years, which allowed us to compare the expected motion of VB 10 due to parallax and proper motion with the observed motion and to compute precise deviations. The achieved single-epoch precisions of our observations are about 0.1 mas and the data showed no significant residual trend, while the presence of the planet should have induced an apparent proper motion larger than 10 mas/yr. Subtraction of the predicted orbital motion from the observed data produces a large trend in position residuals of VB 10. We estimated the probability that this trend is caused by random noise. Taking all the uncertainties into account and using Monte-Carlo resampling of the data, we are able to reject the existence of VB 10b with the announced mass of 6.4 M_J with the false alarm probability of only 0.0005. A 3.2 M_J planet is also rejected with a false alarm probability of 0.023.Comment: 6 pages, 6 figures, 2 tables, accepted for publication in A&

Determination of anthropogenic changes on the urbanized territories using GIS technology

The research aim is to obtain a cartographic model of an urbanized territory by means of thermal survey in an infrared range. With this cartographic model, it will be then possible to reduce the zones in the urbanized territories differing in the level of superficial heat. Further, we will be able to reduce the proof thermal anomalies and thermal structures of the localities that are related to the natural and anthropogenic systems. On the examples of the cities of Ukraine – Energodar and Nikopol, we defined the sources of caloradiances from major industrial concerns as well as from thermal and nuclear power plants. For comparison, we built the model of thermal structure of the city of Tokai and the nuclear power plant with the same name Tokai (Japan). The sources of caloradiances can be, for example, pipes of thermal power stations, ponds-coolers, corps of steel-making production, and other similar objects. If the sizes of such source are known, then we are able to get the absolute values of temperatures

INNOVATIVE BLENDED LEARNING METHODOLOGY IN TEACHING IT STUDENTS ENGLISH FOR PROFESSIONAL PURPOSES

The purpose of this article is to analyze the history of the methodology and the concept of Blended Learning, give examples, systematize, classify and identify the most effective models of blended learning in teaching English to IT students based on the study of their research and use in higher education all over the world. The article proves the necessity of finding innovative technologies for the effective teaching of a professionally oriented foreign language in the field of Information Technologies. Methodical literature, speeches, reports and reports at modern educational conferences, forums are analyzed. The article shows the advantages and disadvantages of using these models, offers examples of research technology Blended Learning. The difference between traditional, distance and blended learning is characterized and shown. Examples are given and models of blended learning are shown schematically. The specifics of the organization of work with one of the resources in the context of blended learning are considered.The purpose of this article is to analyze the history of the methodology and the concept of Blended Learning, give examples, systematize, classify and identify the most effective models of blended learning in teaching English to IT students based on the study of their research and use in higher education all over the world. The article proves the necessity of finding innovative technologies for the effective teaching of a professionally oriented foreign language in the field of Information Technologies. Methodical literature, speeches, reports and reports at modern educational conferences, forums are analyzed. The article shows the advantages and disadvantages of using these models, offers examples of research technology Blended Learning. The difference between traditional, distance and blended learning is characterized and shown. Examples are given and models of blended learning are shown schematically. The specifics of the organization of work with one of the resources in the context of blended learning are considered

High-precision astrometry on the VLT/FORS1 at time scales of few days

We investigate the accuracy of astrometric measurements with the VLT/FORS1 camera and consider potential applications. The study is based on two-epoch (2000 and 2002/2003) frame series of observations of a selected Galactic Bulge sky region that were obtained with FORS1 during four consecutive nights each. Reductions were carried out with a novel technique that eliminates atmospheric image motion and does not require a distinction between targets and reference objects. The positional astrometric precision was found to be limited only by the accuracy of the determination of the star photocentre, which is typically 200-300 microarcsec per single measurement for bright unsaturated stars B=18-19. Several statistical tests have shown that at time-scales of 1-4 nights the residual noise in measured positions is essentially a white noise with no systematic instrumental signature and no significant deviation from a Gaussian distribution. Some evidence of a good astrometric quality of the VLT for frames separated by two years has also been found. Our data show that the VLT with FORS1/2 cameras can be effectively used for astrometric observations of planetary microlensing events and other applications where a high accuracy is required, that is expected to reach 30-40 microarcsec for a series of 50 frames (one hours with R filter).Comment: 11 pages, 9 figures, accepted for publication in A&

Filtration of atmospheric noise in narrow-field astrometry with very large telescopes

This paper presents a non-classic approach to narrow field astrometry that offers a significant improvement over conventional techniques due to enhanced reduction of atmospheric image motion. The method is based on two key elements: apodization of the entrance pupil and the enhanced virtual symmetry of reference stars. Symmetrization is implemented by setting special weights to each reference star. Thus a reference field itself forms a virtual net filter that effectively attenuates the image motion spectrum. Atmospheric positional error was found to follow a power dependency ~ R^{K \mu /2} D^{-K/2+1/3} on angular field size R and aperture D; here K is some optional even integer 2<=K<=sqrt{8N+1}-1 limited by a number N of reference stars, and \mu <= 1 is a term dependent on K and the magnitude and sky star distribution in the field. As compared to conventional techniques for which K=2, the improvement in accuracy increases by some orders. Limitations to astrometric performance of monopupil large ground-based telescopes are estimated. The total atmospheric and photon noise for at a 10 m telescope at good 0.4" seeing was found to be, depending on sky star density, 10 to 60 microarcsec per 10 min exposure in R band. For a 100 m telescope and FWHM=0.1" (low-order adaptive optics corrections) the potential accuracy is 0.2 to 2 microarcsec.Comment: 18 pages, 17 figure

Astrometric precision of observations at VLT/FORS2

In this paper we test the astrometric precision of VLT/FORS2 observations using a serie of CCD frames taken in Galactic bulge area. A special reduction method based on symmetrization of reference fields was used to reduce the atmospheric image motion. Positional precision of unsaturated R=16 mag star images at 17 sec exposure and 0.55 arcsec seeing was found to be equal to 300 microarcsec. The total error of observations was decomposed into components. It was shown that astrometric error depends largely on the photon centroiding error of the target (250 microarcsec for 16 mag stars) while the image motion is much less (110 microarcsec). At galactic latitudes to about 20 degrees, precision for a serie of frames with a 10 min total exposure is estimated to be 30-50 microarcsec for 14-16 mag stars providing the images are not overexposed and the filter R "special" is used. Error estimates for fields with smaller sky star density are given. We conclude that astrometric observations with large telescopes, under optimal reduction, are never atmospheric limited. The bias caused by differential chromatic refraction and residual chromatism of LADC is considered and expressions valid for correcting color effects in the measured positions are given.Comment: 10 pages, 6 figures, accepted for publication in A&

PROFESSIONALLY ORIENTED EXTENSIVE READING AS A TYPE OF IT STUDENTS’ INDEPENDENT WORK

The present work aims to analyse and describe ways of integrating extensive reading into the high educational process. The article proves the necessity of providing the independent work of students who study Information Technologies in tertiary education as it is a vital and motivating way for students to accumulate professional information, acquire new knowledge, gain valuable experience, and upgrade 21st-century skills. To meet the demands of the global labour market, IT students need to understand documentation and scientific literature. They should be ready to participate in conferences, webinars, masterclasses or meetings, to collaborate and communicate in a team via speaking English as it is the most widespread language in the professional environment. Since IT students are fascinated by their speciality, we suggest reading professional literature as one of the ways of obtaining information and increasing the level of professional competence. The article shows the advantages of extensive reading of professional literature and offers examples of websites with level and content-appropriate texts. The authors confirm the positive and beneficial results of extensive reading as part of IT students` independent work

Astrometric detection of exoplanets from the ground

Astrometry is a powerful technique to study the populations of extrasolar planets around nearby stars. It gives access to a unique parameter space and is therefore required for obtaining a comprehensive picture of the properties, abundances, and architectures of exoplanetary systems. In this review, we discuss the scientific potential, present the available techniques and instruments, and highlight a few results of astrometric planet searches, with an emphasis on observations from the ground. In particular, we discuss astrometric observations with the Very Large Telescope (VLT) Interferometer and a programme employing optical imaging with a VLT camera, both aimed at the astrometric detection of exoplanets. Finally, we set these efforts into the context of Gaia, ESA's astrometry mission scheduled for launch in 2013, and present an outlook on the future of astrometric exoplanet detection from the ground.Comment: 9 pages, 3 figures. Invited contribution to the SPIE conference "Techniques and Instrumentation for Detection of Exoplanets VI" held in San Diego, CA, August 25-29, 201