D. L. Gorshanov's research while affiliated with Russian Academy of Sciences and other places

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.

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.

The ExoClock project has been created to increase the efficiency of the Ariel mission. It will achieve this by continuously monitoring and updating the ephemerides of Ariel candidates, in order to produce a consistent catalog of reliable and precise ephemerides. This work presents a homogenous catalog of updated ephemerides for 450 planets, generated by the integration of ∼18,000 data points from multiple sources. These sources include observations from ground-based telescopes (the ExoClock network and the Exoplanet Transit Database), midtime values from the literature, and light curves from space telescopes (Kepler, K2, and TESS). With all the above, we manage to collect observations for half of the postdiscovery years (median), with data that have a median uncertainty less than 1 minute. In comparison with the literature, the ephemerides generated by the project are more precise and less biased. More than 40% of the initial literature ephemerides had to be updated to reach the goals of the project, as they were either of low precision or drifting. Moreover, the integrated approach of the project enables both the monitoring of the majority of the Ariel candidates (95%), and also the identification of missing data. These results highlight the need for continuous monitoring to increase the observing coverage of the candidate planets. Finally, the extended observing coverage of planets allows us to detect trends (transit-timing variations) for a sample of 19 planets. All the products, data, and codes used in this work are open and accessible to the wider scientific community.

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 is based on 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, some of them were recalculated, new ones were added. For the stars of Pulkovo program of observations with a 26-inch refractor, the Gaia DR2 data were analised. Based on these data, the orbits of 16 stars were calculated. In 20 cases from 67, the quasi-instant motion according to the Gaia DR2 data at the instant 2015.5 contradicts the motion according to all-world observations. A possible reason is the presence of inner subsystems. The orientation of the obtained orbits in the galactic coordinate system is also given.

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.

The ExoClock project has been created with the aim of increasing the efficiency of the Ariel mission. It will achieve this by continuously monitoring and updating the ephemerides of Ariel candidates over an extended period, in order to produce a consistent catalogue of reliable and precise ephemerides. This work presents a homogenous catalogue of updated ephemerides for 450 planets, generated by the integration of $\sim$18000 data points from multiple sources. These sources include observations from ground-based telescopes (ExoClock network and ETD), mid-time values from the literature and light-curves from space telescopes (Kepler/K2 and TESS). With all the above, we manage to collect observations for half of the post-discovery years (median), with data that have a median uncertainty less than one minute. In comparison with literature, the ephemerides generated by the project are more precise and less biased. More than 40\% of the initial literature ephemerides had to be updated to reach the goals of the project, as they were either of low precision or drifting. Moreover, the integrated approach of the project enables both the monitoring of the majority of the Ariel candidates (95\%), and also the identification of missing data. The dedicated ExoClock network effectively supports this task by contributing additional observations when a gap in the data is identified. These results highlight the need for continuous monitoring to increase the observing coverage of the candidate planets. Finally, the extended observing coverage of planets allows us to detect trends (TTVs - Transit Timing Variations) for a sample of 19 planets. All products, data, and codes used in this work are open and accessible to the wider scientific community.

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