In this article, we present the results of astronomical seeing measurements conducted at the Maidanak observatory and the influence of meteorological parameters on astronomical seeing. A differential image motion monitor (DIMM) was used to measure astronomical seeing. Astronomical seeing observations were made between 2018–2022, mainly in the summer and autumn months. A total of 266 night observations were conducted between 2018 and 2022. For the whole time frame, the median seeing value was 0.69 arc seconds. With a median value of 0.65″, 2019 is the year with the best seeing, and 2021 has the worst seeing (0.71″). Analysis of long-term variations of the amount of clear time revealed a small trend of decrease in the amount. The correlation between the meteorological parameters and seeing was analyzed. It was determined that the meteorological parameters with the greatest impact on the seeing are wind speed and nighttime temperature variation. The correlation coefficient was equal to 13% and 21% for both quantities. It was found that wind direction and temperature have a relatively weak correlation with astronomical seeing.

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Astronomical Seeing and Meteorological Parameters at Maidanak Observatory

Атмосферное качество астрономического изображения было исследовано с помощью прибора DIMM — измерите- ля дифференциальных дрожаний звезд для оценки интегральной турбулентности над обсерваторией. Была также изучена приземная составляющая данного параметра путем сравнения оценок качества изображения, полученного на разных высотах. Оценено влияние скорости приземного ветра на приземную турбулентность. Кроме того, про- веден статистический анализ скорости и направления ветра в тропопаузе (уровень слоя с атмосферным давлением 200 мБ) в период времени с 1957 по 2002 гг. по данным базы ERA5 и изучено влияние этого ветра на качество изоб- ражения, измеренного в 1996–2002 гг. Результаты показали, что медианное значение качества изображения по всей атмосфере составило 0.69 угловых секунд. Средняя скорость ветра на уровне тропопаузы равна 29 м/с, доминантное направление — западное. Качество изображения имеет сильную корреляцию со скоростью ветра в приземном слое — коэффициент корреляции составил чуть менее 0.50. Направление ветра заметно не влияет на турбулентность. Изменения скорости и направления ветра на высоте 200 мБ не проявляются в изменениях интегрального качества изображения во всей атмосфере.
 Astronomical seeing has been studied using the DIMM — differential image motion monitor for estimation of the integral turbulence above the observatory. The surface component of this parameter has also been studied by comparing the seeing obtained at different heights. The effect of surface wind speed on surface turbulence has been estimated. In addition, a statistical analysis of the wind speed and direction at the tropopause (the height with the air pressure of 200 mB) carried out for the period from 1957 to 2002 based on data from ERA5, and the effect of this wind on the seeing measured in 1996–2002 are estimated. The results showed that the median seeing across the entire atmosphere was 0.69 arcseconds. The average wind speed at the tropopause level is 29 m/s, the dominant direction is west. The seeing has a strong correlation with the wind speed in the surface layer — the correlation coefficient was slightly less than 0.50. Wind direction does not noticeably affect turbulence. Changes in wind speed and direction at a height of 200 mB does not correlate with the integral seeing in the entire atmosphere.

Astronomical seeing at Maidanak Observatory

В данной работе мы представляем большой набор сеток моделей и их применение в рамках определения пара- метров ветров сверхкритических аккреционных дисков. Модели были рассчитаны с различными радиусами (R ∗ = 5, 20, 40R ⊙ ), скоростями (300, 600 км c −1 ), содержаниями водорода (20%, 40%, 50%, солнечное содержание водоро- да) и металличностями (Z = 0.1 − 1.0Z ⊙ ) для широкого набора температур 16 − 56 кК при темпах потери массы 10 −5 − 10 −4 M ⊙ год −1 . Обсуждается алгоритм выбора оптимальной модели ветра для наилучшего описания наблю- даемого спектра, а также применимость подобных моделей для ультраярких рентгеновских источников.
 In this paper we present a large set of model grids and their application for determination of wind parameters of supercritical accretion disks. The models were calculated with different radii (R ∗ = 5, 20, 40R ⊙ ), velocities (300, 600 km s −1 ), hydrogen abundances (20%, 40%, 50%, solar hydrogen abundance) and metallicities (Z = 0.1−1.0Z ⊙ ) for a wide range of temperatures 16 − 56 kK and mass-loss rates 10 −5 − 10 −4 M ⊙ year −1 . We discuss algorithm for optimal model selection and validity of such models for ultraluminous X-ray sources winds.

Determination of extended atmospheres parameters using model grids

Работа посвящена численному моделированию динамики тороидальных магнитных силовых трубок (МСТ) в аккре- ционном диске молодой звезды типа Т Тельца. Уравнения динамики МСТ записываются с учетом сил плавучести и сопротивления, магнитного поля диска и натяжений внутреннего магнитного поля МСТ. Рассматривается случай эффективного теплообмена с окружающим газом. Структура аккреционного диска рассчитывается с помощью маг- нитогазодинамической (МГД) модели аккреционных дисков Дудорова и Хайбрахманова. Для расчета вертикальной структуры диска используется уравнение состояния политропного газа. Расчеты показывают, что МСТ с радиусом поперечного сечения 0.1H, где H — шкала высоты диска, практически вертикально всплывают к поверхности диска со скоростью до 7 км с −1 . Тонкие МСТ радиусом 0.001H всплывают со скоростями до 20 км с −1 и стягиваются по на- правлению к оси вращения диска. В ходе эволюции МСТ могут расширяться до размеров, сравнимых со шкалой высоты аккреционного диска и формировать неоднородную истекающую замагниченную корону диска. Всплытие МСТ является эффективным механизмом отвода избыточного магнитного потока из внутренних областей диска, где степень ионизации достаточно высока и магнитное поле вморожено в вещество. Концентрация МСТ вблизи оси вращения диска может влиять на генерацию струйных истечений и обуславливать наблюдаемые неоднородности струй.
 This work is dedicated to the numerical simulations of the dynamics of toroidal magnetic flux tubes (MFTs) in the accretion disk of a young T Tauri star. The equations of MFT dynamics take into account the buoyancy and drag forces, the magnetic field of the disk, and the tensions of the internal magnetic field of the MFT. The case of efficient heat exchange with the surrounding gas is considered. The structure of the accretion disk is simulated using the magnetohydrodynamic (MHD) model of the accretion disks developed by Dudorov and Khaibrakhmanov. The equation of state for a polytropic gas is used to model the vertical structure of the disk. Simulations show that MFTs with cross-section radius of 0.1H, where H is the disk scale height, rise almost vertically to the disk surface at a speed of up to 7 km s −1 . Thin MFTs with cross-section radius of 0.001H float up with velocities up to 20 km s −1 and contract towards the axis of rotation. During evolution, MFTs can expand to sizes comparable to the accretion disk scale height and form an inhomogeneous outflowing magnetized disk corona. Floating of MFTs is an effective mechanism for removing excess magnetic flux from the inner regions of the disk, where the ionization fraction is large, and the magnetic field is frozen into gas. The MFT concentration near the disk rotation axis can affect the generation of jet outflows and cause the observed jet inhomogeneities.

Formation and dynamics of magnetic flux tubes in the accretion disks of young stars

В работе представлены предварительные результаты анализа многоцветной BVRI фотометрии звезды MX Her. MX Her = TYC 3519-1418-1 является затменно-двойной системой типа Алголя с периодом обращения компонентов P = 2.3476536 дней, имеющей признаки пульсационной неустойчивости главной звезды. Наблюдения проводились в 2022 г. на телескопе Цейсс-600-Восточный, введенном в строй в том же году на обсерватории Майданак (Узбекистан) в рамках международного сотрудничества с Юннанскими обсерваториями (Китай). В настоящей работе впервые представлены решения многоцветных кривых блеска с помощью программы PHOEBE. В результате моделирования мы получили следующие оценки параметров системы: фотометрическое отношение масс системы M 2 /M 1 = 0.31, отношение эффективных температур T 2 /T 1 = 0.57, наклон орбиты i = 83.8 ◦ и эксцентриситет e = 0.0008.
 The paper presents preliminary results of the analysis of multicolored BVRI photometry of the MX Her star. MX Her = TYC 3519-1418-1 is an Algol-type eclipsing binary system with an orbital period P =2.3476536 days, showing signs of pulsational instability of the main star. The observations were carried out in 2022 on the ZEISS-600-East telescope, put into operation in the same year at the Maidanak Observatory (Uzbekistan) in the framework of international cooperation with the Yunnan Observatories (China). In this paper, solutions of multicolored light curves using the PHOEBE software are presented for the first time. As a result of the simulation, we obtained the following estimates of the system parameters: the photometric mass ratio of the system M 2 /M 1 = 0.31, the ratio of effective temperatures T 2 /T 1 = 0.57, the inclination of the orbit i = 83.8 ◦ and the eccentricity e = 0.0008.

Physical parameters of the MX Her eclipsing binary system obtained from BVRI photometry

The article presents statistics of the astronomical seeing at the Maidanak Observatory in Uzbekistan. Astronomical seeing measurements were performed using a differential image motion monitor. In the period 2018 to 2021, a total number of 204 night observations were carried out. The median zenith seeing for the entire period of observations was found to be 0.69″ (arcseconds). The results were compared with those obtained in the previous measurement period of 1996 to 2003. The comparison shows very small differences between the two measurement sets in the monthly and yearly median values. The best seeing was observed in October, but it was November according to the previous measurements. The best year in terms of seeing was 2019 with its median value 0.65″ and the worst seeing observed in 2021 (0.71″). 

Astronomical seeing at Maidanak Observatory with differential image motion monitor

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Astronomical seeing at Maidanak Observatory with differential image motion monitor