In 2022, the telescope of the Main (Pulkovo) Astronomical Observatory of RAS obtained astrometric and photometric series of observations of a potentially dangerous asteroid (138971) 2001 CB21 during its approach to Earth. Based on the data obtained and data from the MPC website, the asteroid’s orbit was improved and the circumstances of the encounters were investigated with the Earth and Venus and an assessment was made of the influence of nongravitational effects on its motion. Based on photometric observations of the asteroid, a light curve was constructed and its axial rotation period was confirmed: R = 3.305 ± 0.002 h.

Based on the speckle observations of the wide double star ADS 15571 with the 6-m BTA telescope at the Special Astrophysical Observatory of the Russian Academy of Sciences in 2014, we have confirmed the existence of a close companion to component A that was previously detected from astrometric observations at the Pulkovo Observatory. An extension of the BTA observations from 2014 to 2022 has allowed 28 positions of the companion relative to the primary star to be obtained. From this series we have constructed the relative orbit of the companion and determined the sum of the masses of subsystem A ( 1.686± 0.014 M_⊙ ). A comparison of this orbit with the orbit of the photocenter of component A constructed from Pulkovo photographic observations has also allowed the mass ratio of the primary star and the companion and their individual masses to be estimated: M_Aa=(1.10± 0.07) M_⊙ and M_Ab=(0.59± 0.07) M_⊙ . Based on the estimates of the magnitude difference between the two stars of the system ADS 15571A, we have estimated the spectral types of the components: ADS 15571Aa—F8V; ADS 15571Ab—K5V–K5.5V. The speckle observations of component B have shown that it has no resolvable companions.

Optical observations of the occultation of the star TYC 5254-00839-1 by Neptune’s satellite Triton were carried out on October 6, 2022, using the Zeiss-1000 telescope at the Sanglokh Observatory (MPC code 193). As a result of photometric processing of images, a light curve of the star was constructed and it was revealed that the areas of decline and rise in brightness had a finite duration from 15 to 24 s. This is apparently due to the presence of an atmosphere around Triton. In addition, in the resulting light curve of this phenomenon, according to our and other observations, a “step” is revealed, which may indicate the possible presence of a close, faint object near the occulted star. As a result of astrometric processing, high-precision coordinates of Triton were determined at the average moment of occultation, which, within the limits of measurement errors, coincided with its ephemeris position.

The astrometric observations of potentially hazardous asteroid 2001 QQ142 (139622) were made during its apparition after its close approach to the Earth. The observations were made using the mirror astrograph ZA-320M and D.D. Maksutov meniscus telescope MTM-500M of Pulkovo Observatory. The RMS of obtained series of the asteroid positions are σ = ±0''.21 for ZA-320M and σ = ±0''.07 for MTM-500M observations.

The Yarkovsky effect is one of the noticeable factors in the orbital evolution of near-Earth asteroids (NEAs). The A2 non-gravitational parameter describes the corresponding acceleration in the NEA motion model. This parameter can be derived from astrometric observations of the NEA. We present the results of astrometric observations of two NEAs (2010 XC15 and 2014 HK129). The measurements were performed with the MTM-500M telescope (Mountain Astronomical Station of the Pulkovo Observatory). The modified Gaia star apparent approach technique was applied. As a result, the astrometric accuracy of our observations reached the 0.05 arcsec level. It allowed us to estimate the A2 values of the 2010 XC15 asteroid: –139.5 × 10–15 ± 20.2 × 10–15 au/d2. It is in good agreement with the NASA JPL estimate for this asteroid. The 2014 HK129 A2 parameter formal value extracted from our data is 61.3 × 10–15 ± 1583.4 × 10–15 au/d2. Introduction of this A2 value into the asteroid motion model provides a significant decrease (about 0.05–0.1 arcsec) of the (O–C) values for the first epoch of 2014 HK129 observations. It can be considered as faint evidence of the reality of Yarkovsky drift for the 2014 HK129 asteroid.

As part of the Pulkovo program for the study of near-Earth objects, more than 1500 observations of asteroid 2023 BU, which was discovered at the very beginning of 2023 just a few days before its extremely close approach to the Earth at a distance of about 3.5 × 106 m from its surface, were made at the MTM-500M telescope. It was one of the closest encounters of an asteroid with the Earth ever recorded, which caught the attention of astronomers around the world. Based on the observations of this asteroid, its orbit was refined and the orbital evolution was studied. In addition, estimates of the influence of solar radiation pressure and the Yarkovsky effect were made, which is relevant due to the problem of asteroid and comet hazard.

In 2020, two telescopes of the State Astrophysical Observatory of the Russian Academy of Sciences, ZA-320M and MTM-500M, obtained series of observations of the potentially dangerous asteroid 65690 (1991 DG) during its approach to the Earth and carried out their astrometric and photometric processing. Using the coordinates of the asteroid and observations from the MRS site, the orbit of the asteroid was clarified, and the circumstances of the approaches to the Earth and Mars were determined, and an assessment was made of the influence of nongravitational effects on its orbit. Based on the results of photometric processing of the asteroid, a light curve was constructed and the period of its axial rotation was determined: P = 4.3193 ± 0.0028 h.

A near infrared and optical photometric study of Herbig star V517 Cyg has been carried out. Infrared data were obtained in 2003–2017 at the Campo Imperatory Observatory (Italy) with the Pulkovo telescope AZT-24 in Johnson’s \(JHK\) bands. Optical light curves in Johnson \(UBVR\) bands were obtained at the Maidanak observatory. Additional optical photometry from different sources (ASSAS, WISE, and AAVSO) was also used. It was shown that the behavior of V517 Cyg in the near infrared is typical for UX Ori stars. A considerable contribution to the near infrared variability is due to variable extinction along the line of sight, but the disk radiation becomes strong in the \(H\) and \(K\) bands: there is a significant correlation of \(V\) and \(J\) magnitudes (\(r \sim 0.84\)), while \(H\) and \(K\) bands correlates poorly with \(V\) band. The amplitude of variability in \(J\) is quite large (\( \sim {\kern 1pt} {{1.8}^{m}}\)). The deepest minimum (\(\Delta V \sim {{3.6}^{m}}\)) in the \(V\) band demonstrates quasi-periodic variations with an amplitude of \( \sim {\kern 1pt} {{0.8}^{m}}\) and a period of \( \sim {\kern 1pt} 19\) days, the origin of which is still unclear. It is possible that these quasi-periodic variations are related to rotation period of a second companion, a cold T Tauri star. The spectrum V517 Cyg reveals typical for UX Ori stars the double-peaked emission line Hα. The NaI D doublet has inverse P Cyg profiles, indicating intense accretion of gas onto the star. The accretion rate from an equivalent width of the Hα line is \({{\dot {M}}_{{acc}}} = 3.6 \times {{10}^{{ - 8}}}\,{{M}_{ \odot }}\) per year.

Results are presented from a spectroscopic study of the Ae/Be Herbig star HD 259431 conducted from 2010 to 2019 using high-resolution spectrographs at: (a) the Crimean Astrophysical Observatory, (b) European Southern Observatory ESO (Chile), (c) the OAN SPM Observatory in Mexico, and (d) the Kourovskaya Astronomical Observatory at the Urals Federal University. 245 spectra of the object were obtained in the neighborhood of circumstellar lines (mainly, Hα, Hβ, HeI 5876, FeII 4923, and DNaI), as well as some lines from its atmosphere (HeI 4009, 4026). This article is concerned only with analyzing the cyclical variability of the parameters of some circumstellar lines on a time scale of the order of one day. Antiphase variations in the bisector velocity of the emission profile of Hβ and the velocity of the boundary of the red wing of the HeI 5876 absorption line is observed. A period P = 2.839 days is found in these variations. Assuming that this value may be the period of rotation of the star, an angle of inclination of the axis of rotation to the line of sight of i = 48° ± 7° is estimated. Since at different phases of this period the profiles of Hβ and Hγ looked like either a PCyg-profile or a double emission with a depression on the red side, it was suggested that the observed variability is associated with the existence of a magnetosphere around HD 259431, which has an inclination of the magnetic axis relative to the axis of rotation. In this case over one rotation of the star, along the line of sight an accretion and then an outflow flux of matter occurs, since the regions with these two types of kinematics according to the model lie at different magnetic latitudes. The existence of the magnetosphere is supported by the very high velocities of the boundary of the red wing of the HeI 5876 absorption line (up to +400 km/s), observed at the phases when an accretion flow is on the line of sight. It was found that similar variations are also manifested by the Hδ, HeI 6678, and OI 7773 lines. At the same time, in a number of lines formed in the circumstellar medium, far from the region of the disk/star interaction region, this kind of cyclical variability was not observed. We note that this is the first case of detecting a magnetosphere in a Be Herbig star of such an early class (B6). Earlier it was assumed that magnetospheres cannot be observed in Be Herbig stars. Keywords: Ae/Be Herbig stars: circumstellar shells: disk accretion: wind: HD 259431

Summed many years of work at Pulkovo, the orbits of 67 wide pairs of visual double and multiple stars (included in 64 systems) which were obtained by the Apparent Motion Parameters (AMP) method are presented. This short arc orbit determination method uses the most reliable astrometric and astrophysical data corresponding to one instant of time. The rest of the observations accumulated in the world serve to control the quality of the orbit and refine some parameters. All early determined AMP-orbits were compared with new observations, part of them recalculated, new orbits added. For the stars of Pulkovo program of observations with a 26-inch refractor, the data from the Gaia DR2 catalog were analised. The orbits of 16 stars were calculated on these data. The direction of the motion derived from Gaia DR2 at the instant 2015.5 contradicts to the series of all observations for 20 stars. The probable reason is in the presence of inner subsystems. The orientation of the obtained orbits in the Galaxy frame is also given.

This paper presents the results of the study of long-term photometric activity in the near infrared spectral region of the young Herbig Ae star VX Cas belonging to the family of irregular UX Ori variables. The infrared data were obtained in 2003–2017 at the Campo Imperatore Observatory (Italy) using the Pulkovo telescope AZT-24 in Johnson’s photometric bands $$JHK$$ . Additional optical photometry from various sources was used as well. It was shown that the observed photometric activity of the star in the $$J$$ band and partly in the $$H$$ band was caused mainly by variations in circumstellar extinction in the protoplanetary disk. In a number of episodes, anticorrelation was observed between brightness variations in the optical $$V$$ band and $$H$$ and $$K$$ bands: the brightness in the $$H$$ and $$K$$ bands increased with weakening of the brightness in the $$V$$ band. This indicates that the gas and dust clouds that screened the star from the observer consisted of hot dust and were located near the sublimation zone.

Представлены результаты выявления астероидов, потенциально опасных для внутренних планет. Исследовано орбитальное движение астероида 2022 АЕ1, троянцев Земли (2010 TK7, 2020 XL5) и «рукотворного» астероида 2020 SO. The results of the detection of potentially hazardous asteroids for the inner planets are presented. The orbital motion of asteroid 2022 AE1, the Earth Trojans (2010 TK7, 2020 XL5), and the “man-made” asteroid 2020 SO has been studied.

The astrometric and photometric series of observations of potentially hazardous asteroid (276033) 2002 AJ129 were obtained with MTM-500M telescope of Pulkovo Observatory in the period of its close approach to the Earth on February 4, 2018. The orbital evolution was studied and the influence of non-gravitational effects (solar ra-diation pressure and the Yarkovsky effect) was estimated. The axial rotation period (P = 3.9222 +/- 0.0008 h) of the asteroid and the color indices (B-V = 0.687 +/- 0.050, V-R = 0.405 +/- 0.027, R-I = 0.178 +/- 0.044) were determined from the photometric series of observations.

This paper is a continuation of our earlier work devoted to determining the orbit and mass of the star 61 Cyg and the changes in the photometric characteristics of its components. The purpose of this work has been to refine the orbital elements, estimate the masses, and search for possible manifestations of periodic components in deviations from the orbital motion. Observations on two instruments at the Pulkovo Observatory have been used in this work: the normal astrograph during 1895-1919 and the 26-inch refractor during 1957-2019, as well as the earliest micrometric measurements by V. Ya. (F.G.W.) Struve during 1819-1837. Relative positions of the components determined from observations with the normal astrograph during 1895-1999 are published for the first time. Because of its closeness to the Sun and the spectral class of the components K5V and K7V, 61 Cyg is regarded as a probable candidate parent star of an exoplanet. Because of the combined observations with the 26-inch refractor and the transformation of all the data to a unified system, a gap in the observations from the beginning of the twentieth century has been filled. The modern astrophysical parameters of this star together with data published in the Gaia DR2 survey have been used. To check the orbit, the radial orbital acceleration W has been calculated from our data and found to be in good agreement with the acceleration derived by other authors from spectral observations. Possible periodic deviations from the orbital motion of the star are also discussed.

In the frame of this study astrometric observations of an unusual object 2020 SO - a newly discovered asteroid that turned out to be a Centaur upper-stage booster from 1960s - during its two close approaches to the Earth in December, 2020 and February, 2021 were carried out using two telescopes of Pulkovo observatory. The orbit of the object in question was determined and its future orbital evolution was modelled.

Results are presented from a study of the binary star ADS 7251 (STF 1321) based on a uniform series of observations on the 65-cm refractor at Pulkovo from 1962 through 2018. The errors in the yearly average positions ρ and θ are equal to 0′′.004 and 0°.02 for the photographic and 0.”003 and 0.°01 for the CCD observations. A new orbit is calculated from the found relative position and the exact parallax of Gaia. The comparisons use modern observations of Hipparcos and Gaia, as well as observations from the distant past in the nineteenth century by Struve. This study yielded better convergence with the distant observations when the Gaia parallax was used. The errors calculated from O-C are 0′′.008 ÷ 0′′.011 . They are comparable to those obtained for other binary stars close to the sun, as well as to the corresponding estimates for stars rotating around the central body of the galaxy and observed on the Keck and VLT telescopes. The importance of observations of the components A and B of ADS 7251 as possible parent stars for exoplanets is noted.

The asteroid (13553) Masaakikoyama was observed with the ZA-320M and MTM-500M telescopes of the Pulkovo observatory in August and September 2018. Its axial rotation period was estimated based on the observed sections of the light curve (and additional observational data provided by B.D. Warner) at 97.2 ± 0.3 h. This estimation was made difficult by the fact that the period is commensurable with a day. The light curve has certain features suggestive of tumbling rotation and a complex shape. The orbit of (13553) Masaakikoyama was improved using the obtained astrometric positions of the asteroid.