We report observations of color in the inner coma of Comet C/2013 UQ4 (Catalina) with the broadband B and R filters. We find significant temporal variations of the color slope, ranging from -12.67 ± 8.16% per 0.1 m up to 35.09 ± 11.70% per 0.1 m. It is significant that the comet changes color from red to blue over only a two-day period. Such dispersion cannot be characterized with an average color slope. We also observe Comet C/2013 UQ4 (Catalina) in infrared using Spitzer and find no significant CO/CO 2 gaseous species in its coma. Therefore, we classify Comet C/2013 UQ4 (Catalina) as a dust-rich comet and attribute the measured color slope to its dust. We analyze the color slope using the model of agglomerated debris particles and conclude that the C/2013 UQ4 coma was chemically heterogeneous, consisting of at least two components. The first component producing the bluest color is consistent with Mg-rich silicates.There are three different options for the second component producing the reddest color. This color is consistent with either Mg-Fe silicates, kerogen type II, or organic matter processed with a low dose of UV radiation.

At present, сhlorophyll meters are widely used for a quick and nondestructive estimate of the chlorophyll (Chl) content in plant leaves. Chlorophyll meters allows to estimate the Chl content in relative units -the chlorophyll index (CI). However, using such meters, one can face a problem of converting the CI into the absolute values of the pigment content and comparing the data acquired with different devices and for different plant species. Many Chl meters (SPAD-502, CL-01, CCM-200) demonstrated a high degree of correlation between the CI and the absolute pigment content, and a number of formulas have been deduced for different plant species to convert the CI into the absolute value of the photosynthetic pigment content. However, such data have not yet been acquired for the atLEAF+ chlorophyll meter. The purpose of the present research was to assess the applicability of the atLEAF+ Chl meter for estimating Chl content. A significant speciesspecific exponential relationships between the atLEAF value (corresponding to CI) and extractable Chl a, Chl b, Chl (a+b) for Calamus dioicus and Cleistanthus sp. were shown. The correlations between the atLEAF values and the content of Chl a, Chl b, and Chl (a+b) per unit of leaf area was stronger than per unit of dry leaf mass. The atLEAF value-Chl b correlation was weaker than that of atLEAF value-Chl a and atLEAF value-Chl (a+b) correlations. The influence of light conditions (Chl a/b ratio) on the atLEAF value has also been shown. The obtained results indicate that on condition of the right calibration the atLEAF+ Chl meter is a cheap and convenient tool for a quick nondestructive estimate of Chl content and can be used for this purpose along with other Chl meters.

Context. The rotation state of small asteroids is affected by the Yarkovsky–O’Keefe–Radzievskii–Paddack (YORP) effect, which is a net torque caused by solar radiation directly reflected and thermally reemitted from the surface. Due to this effect, the rotation period slowly changes, which can be most easily measured in light curves because the shift in the rotation phase accumulates over time quadratically. Aims. By new photometric observations of selected near-Earth asteroids, we want to enlarge the sample of asteroids with a detected YORP effect. Methods. We collected archived light curves and carried out new photometric observations for asteroids (10115) 1992 SK, (1620) Geographos, and (1685) Toro. We applied the method of light curve inversion to fit observations with a convex shape model. The YORP effect was modeled as a linear change of the rotation frequency υ ≡ dω∕dt and optimized together with other spin and shape parameters. Results. We detected the acceleration υ = (8.3 ± 0.6) × 10−8 rad d−2 of the rotation for asteroid (10115) 1992 SK. This observed value agrees well with the theoretical value of YORP-induced spin-up computed for our shape and spin model. For (1685) Toro, we obtained υ = (3.3 ± 0.3) × 10−9 rad d−2, which confirms an earlier tentative YORP detection. For (1620) Geographos, we confirmed the previously detected YORP acceleration and derived an updated value of υ with a smaller uncertainty. We also included the effect of solar precession into our inversion algorithm, and we show that there are hints of this effect in Geographos’ data. Conclusions. The detected change of the spin rate of (10115) 1992 SK has increased the total number of asteroids with YORP detection to ten. In all ten cases, the dω∕dt value is positive, so the rotation of these asteroids is accelerated. It is unlikely to be just a statistical fluke, but it is probably a real feature that needs to be explained.

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Открытый в ноябре 2018 г. дамоклоид A/2018 V3 может быть примером стареющей долгопериодической кометы или материала астероидного происхождения из облака Оорта (кометой-Мэнксом); оба типа объектов изучены лишь в незначительной степени. Абсолютный блеск A/2018 V3 оценён как H V = 15,69 ± 0,10 и диаметр 0,3 0,2 D 4,8 + − = км (сравнимо с диаметрами ядер множества наблюдаемых долгопериодических комет). Здесь мы даём рекомендации к планированию наблюдений A/2018 V3 в 2019 г., в котором сложатся благоприятные условия видимости объекта в обоих полушариях Земли (в том числе произойдёт сближение с нашей планетой до Δ = 0,38). В частности, приводится вероятная кривая блеска A/2018 V3 вблизи его сближения с Землёй и перигелия (июль-октябрь 2019 г.), когда потенциальная комета должна стать достаточно яркой для ПЗС-фотометрии с небольшими телескопами и визуальных наблюдений (m1~13 в максимуме). При построении кривой мы опирались на характеристики стареющей долгопериодической кометы C/2013 UQ 4 (Catalina). В первые месяцы 2019 г. рекомендуются наблюдения с крупными телескопами для поисков возможных признаков появляющейся кометной активности, вблизи сближения-мультиволновые фотометрические наблюдения.