Перегляд за Автор "Kleshchonok, V. V."

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    Observation of an occultation of the UCAC4 488-082551 star by asteroid (76228) 2000 EH 75 on 31 May 2022
    (Одеський національний університет імені І. І. Мечникова, 2022) Gorbanev, Yuriy M.; Kleshchonok, V. V.; Kimakovsky, S. R.; Горбаньов, Юрій Михайлович
    Observations of an occultation of the UCAC4 488-082551 star by asteroid (76228) 2000 EH 75 were carried out on 31 May 2022 at Kryzhanivka observation station of Odesa I. I. Mechnykov National University (the observatory code A85). A set of instruments, which included a Schmidt telescope (the primary mirror diameter D = 271.25 mm; the corrector plate diameter Dk = 223.9 mm; the focal length F = 440 mm), a GPS receiver and Videoscan-415-2001 CCD camera, was used to perform observations. The observing conditions were as follows: clear sky, the star’s altitude 490 south, the Moon was below the local horizon. The target star from the UCAC4 catalogue (Zacharias et al. 2013) has the following photometric parameters: mB = 14.008; mv = 12.720; mr = 12.284; m, = 11.813. The diameter of the star has not been determined. Asteroid (76228) is a Main Belt asteroid with an orbital period of 4.17178 years. It has an absolute magnitude of 14.93, the visible geometric albedo of 0.123±0.013 and diameter of 5.00±0.23 km (Masiero et al. 2011). The time of occultation predicted using ephemerides was 23:52:44±4 sec. The maximum duration of the occultation was 0.4 sec, provided that the observing site was located at the centre of the occultation track (strip). A drop in the star’s brightness observed during occultation was about 8m. The occultation event was recorded as a sequence of GIF images with the exposure time of 0.5 sec per frame. The system clock of the computer used for the occultation recording was controlled with a GPS receiver in a fashion similar to that described in the paper by Karbovsky et al. (2017). The data processing yielded an estimate of the occultation duration of 0.46±0.04 sec. The uncertainty of the occultation start time within exposure results in the total estimate of accuracy in timing the maximum phase of occultation 23:52:44.06±0.10 sec. The chord length across the asteroid estimated by timing the occultation is L = 9.2±0.8. This chord length is close to the estimates of the asteroid diameter reported in the paper by Masiero et al. (2011).
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    Specific features of structures in the inner coma of comet C/2017 T2 (panstarrs) as observed with the OMT-800 telescope of the Odessa Observatory telescope network
    (Одеський національний університет імені І. І. Мечникова, 2020) Kleshchonok, V. V.; Kashuba, S. G.; Andrievsky, S. M.; Gorbanev, Yu. M.
    Observations of the comet were carried out using the OMT-800 telescope (the primary mirror diameter D = 80 cm; the focal length F = 214 cm) of the Odessa Observatory telescope network from January to June 2020. Image processing was performed through standard methods using subtraction of dark and flat field frames. The resulting frames were employed to analyse the morphology of the cometary inner coma using digital filters. Isophotes of the coma and images of its structures appearing as fans and jets were obtained. The presence of a strong fan, which distorts the coma’s standard appearance and makes it elongated perpendicularly to the Sun-comet line, is observed over the period from January to April. Later on, a weak jet that hardly affects the coma’s standard shape appears to replace the fan. The jet reaches its peak intensity near perihelion and then gets fainter rapidly. Such behaviour of the coma structures is indicative of the presence of two active areas on the cometary nucleus surface, for which the matter outflow is governed by the Sun illumination conditions. One of these areas, being more active, is responsible for the appearance of a strong fan. The other area, which is far less active, generates a jet that manifests itself near perihelion. The peak dust production of the comet 120-150 days before perihelion is due to the presence of an active fan in the inner coma.