arXiv subjects

Valerii Kleshchonok

Publications and source records attributed to Valerii Kleshchonok.

3 recordsLinked to original sources

arXiv2026

Dust, gas activity and morphology of comet 12P/Pons-Brooks at heliocentric distances beyond 1.1 au

Comet 12P/Pons-Brooks is a periodic comet with an orbital period of approximately 71 years. Because of the period duration, aphelion of 35.3 au, and highly inclined orbit (74.2 deg), it is classified as a Halley-type comet. In this work, we present the results of the analysis of photometric and spectral observations of comet 12P/Pons-Brooks while it was at a heliocentric distance beyond 1.1 au, before perihelion passage. Quasisynchronous observations were carried out from July 2023 to March 2024 using 0.61-m and 1.3-m telescopes at the Skalnaté Pleso Observatory, 1-m telescope Zeiss-1000 Sanglokh International Astronomical Observatory, and 0.7-m telescope AZT8 at the observation station of Taras Shevchenko National University of Kyiv. Photometric observations were conducted using B, V, and R filters of the Johnson-Cousins and Bessel photometric systems. We completed our data collection with broadband photometric and spectral observations on the 2-m HCT telescope at the Indian Astronomical Observatory. During this period, the dust coma morphology and photometric data measured in the R filter, such as the apparent, absolute magnitudes and dust activity level, indicate several repeated outbursts in brightness and dust activity occurred around July 22, September 25, October 17-23, and a significant outburst was recorded on November 1-7. We detected strong gas emission features in the cometary spectrum belonging to CN, C2, and C3 molecules. Furthermore, gas production rates of these molecules were estimated using Haser's model. A comparison of dust activity level and CN gas production rate shows that dust activity increased significantly as the comet approached the Sun, while gas activity exhibited more moderate changes.

astro-ph.EP↗

arXiv2025

A comprehensive study of comet 67P/Churyumov-Gerasimenko in the 2021/2022 apparition. I. Photometry, spectroscopy, morphology

We present observations of comet 67P/Churyumov-Gerasimenko during its 2021/22 apparition, aiming to investigate its dust and gas environment and compare the results with those obtained in 2015/16 using the same telescope. Quasi-simultaneous photometric, spectroscopic, and polarimetric observations were carried out at the 6-m BTA SAO telescope. The comet was observed on 6 October 2021, 31 days before perihelion, with \textit{g}-SDSS and \textit{r}-SDSS filters, and on 6 February 2022, 96 days after perihelion, using narrowband cometary filters: BC ($\lambda4450/62$~Å), RC ($\lambda6839/96$~Å), and CN ($\lambda3870/58$~Å). These were complemented by images from the 2-m Liverpool Telescope (La Palma). On 6 October 2021, a sunward jet and long dust tail were detected. By 6 February 2022, the dust coma morphology had changed noticeably, revealing a bright sunward neckline structure superimposed on the projected dust tail, along with two jets at position angles of 133$^{\circ}$ and 193$^{\circ}$. Spectra showed strong CN emission, with relatively weak C$_2$, C$_3$ and NH$_2$ emissions. The dust production rate $Afρ$ did not exceed 200~cm (uncorrected for phase angle) in both epochs. An unusual CN coma morphology was observed, with evidence of an additional CN source associated with dust jets. Geometric modeling of the jets' dynamics indicated an active area at latitude $-70^{\circ} \pm 4^{\circ}$ with a jet opening angle of $20^{\circ} \pm 6^{\circ}$ on 6 October 2021, and two active areas at latitudes $-58^{\circ} \pm 5^{\circ}$ and $-53^{\circ} \pm 10^{\circ}$, separated by longitude $150^{\circ} \pm 20^{\circ}$, producing the observed jets on 6 February 2022. The average particle velocity in the jets was about $0.32 \pm 0.04$~km~s$^{-1}$.

astro-ph.EP↗

arXiv2021

Comet 2P/Encke in apparitions of 2013 and 2017: I. Imaging photometry and long-slit spectroscopy

We present the results of imaging photometric and long-slit spectroscopic observations of comet 2P/Encke performed at the heliocentric distance 0.56 au, geocentric distance 0.65 au, and phase angle 109.2 deg on November 4, 2013 and at 1.05 au, 1.34 au, and 46.8 deg on January 23, 2017. Observations were carried out at the 6-m BTA telescope of the Special Astrophysical Observatory (Russia) with the multimode focal reducer SCORPIO-2. In 2013, the direct images of comet Encke were obtained with the broad-band V filters, whereas in 2017 the narrow-band cometary BC, RC, and NH2 filters as well as the medium-band SED500 and broad-band r-sdss filters were used for observations. About 60 emissions belonging to the CN, C2, C3, NH2, CH, and CO+ molecules were identified within the range 3750-7100 Å. The ratios of the production rates C2/CN and C3/CN correspond to the typical comets, not depleted in the carbon-chain. A complex structure of the coma was detected in both observational periods. In January 2017, the dust was in general concentrated near the nucleus, the dust/gas ratio was 2.9 in the r-sdss filter, however, this ratio was larger than 1 at distances 3000-40000 km from the nucleus. We found that about 75% of the flux of the reflected light in the central pixel was due to the nucleus, whereas the nucleus's flux contributed 48% in the total intensity of the 2000 km area of the coma. We found that after correction for the dust coma contamination the nucleus magnitude is 18.8m+/-0.2m.

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