The influence of the anisotropic β‐effect in the rotating magnetoconvection problems is studied. Several models of rotating magnetoconvection with different types of anisotropy are presented. A comparison among them is performed. We stress the difference, especially about the magnetoconvection models where there is anisotropy in the turbulent magnetic diffusivity. The influence on convection is thoroughly

We present our final orbit for the late‐type spectroscopic binary Henry Draper one (HD 1). area total of 553 spectra from 13 years of observations are used with our robotic STELLA facility and its high‐resolution echelle spectrograph SES. Its long‐term radial velocity stability is ≈50 m s−1. A single radial velocity of HD 1 reached an rms residual of 63 m s−1, close to the expected precision. Spectral

In 2015, a radial velocity monitoring campaign was started in order to redetermine and/or constrain the orbital solutions of spectroscopic binary systems. The observations were carried out at the University Observatory Jena with the Échelle spectrograph FLECHAS. The results from the main part of our target sample are already published. For the final target of this campaign, θ Cep, we can now present

The first results of a new survey, which explores the second data release of the ESA‐Gaia mission, are reported in order to search for stellar companions of (Community) TESS Objects of Interest and to characterize their properties. In total, 193 binary and 15 hierarchical triple star systems are presented, detected among 1,391 target stars, which are located at distances closer than about 500 pc around

Issues in applying the Gaia DR2 data to determine the main parameters of open star clusters and the use of a formal, two‐color diagram for the initial selection of cluster members are discussed. The possibility of using the catalog estimates of interstellar absorption is considered. It has been shown that these estimates correlate with the E(B − V) values; therefore, E(B − V) values known for many

We present a deep (50‐hr exposed) image of the nearby spiral galaxy M 63 (NGC 5055), taken with a 0.14‐m aperture telescope. The galaxy halo exhibits the known, very faint system of stellar streams extending across 110 kpc. We found five very low‐surface‐brightness dwarf galaxies around M 63. Assuming they are satellites of M 63, their median parameters are: absolute B‐magnitude −8.8 mag, linear diameter

The derivation of the phenomena in Hipparchus' Commentary on the phenomena of Aratus and Eudoxus from the star positions of his presumed star catalog is investigated under the assumption of their determination by a star globe. As most of Hipparchus' star coordinates are not available, they are reconstructed from the star catalog in Ptolemy's Almagest. Data consistent with the assumed determination

Dynamically different groups of comets and active asteroids with orbits at 2–5 a. u. show dust activity in varying degrees and forms. A photometric study and comparison of physical parameters can help to classify the mechanisms and nature of the activity for such objects. We present new observations using broadband photometry of 15 active objects in the main asteroid belt and surrounding regions obtained

We have reanalyzed the data used by Bessel, von Struve, and Henderson in the 1830s to measure the first parallax distances to stars. We can generally reproduce their results, although we find that von Struve and Henderson have underestimated some of their measurement errors, leading to optimistic parallax uncertainties. We find that temperature corrections for Bessel's measured positions are larger

The hot Jupiter HD 217107 b was one of the first exoplanets detected using the radial velocity (RV) method, originally reported in the literature in 1999. Today, precise RV measurements of this system span more than 20 years, and there is clear evidence of a longer‐period companion, HD 217107 c. Interestingly, both the short‐period planet (Pb ∼ 7.13 d) and long‐period planet (Pc ∼ 5059 d) have significantly

Nitrogen is a biosignature gas that cannot be maintained in its Earth‐like ratio with CO2 under abiotic conditions. It has also been proven to be notoriously hard to detect at optical and infrared wavelengths. Fortunately, the ultraviolet region, which has only recently started being explored for terrestrial exoplanets, may provide new opportunities to characterize exoplanetary atmospheric nitrogen

The high excitation levels that form the O i and C i lines seen in RR Lyrae stars have long been known not to obey local thermodynamic equilibrium (LTE) statistics. We have observed 21 RR Lyrae and related stars with the Apache Point Observatory echelle spectrograph on the 3.5‐m telescope and, for the first time, have derived abundances using non‐local thermodynamic equilibrium (NLTE) analyses in conjunction

Young nearby runaway stars are suitable to search for their place of origin and possibly associated objects, for example, neutron stars. Tetzlaff et al. (2011) selected young (≤50 Myr) runaway star candidates from Hipparcos, for which they had estimated the ages from the location in the Hertzsprung‐Russell diagram and evolutionary models. Here, we redetermine or constrain their young ages more precisely

We study the star formation efficiency per free‐fall time(ϵff) of a self‐gravitating molecular cloud (MC) in the presence of dimensionless thermodynamic efficiency factor ϵ, quantified by taking the ratio of radiation luminosity to the gravitational energy released per free‐fall time (i.e., ) where 0 < ϵ < 1. The results of previous studies indicated that theoretically calculated star formation efficiency

We present the numerical study of the formation of a spiral structure in the context of violent relaxation. Initial conditions are the out‐of‐equilibrium disks of self‐gravitating particles in rigid rotation. Using that mechanism, robust and nonstationary spiral arms can be formed within a few free‐fall times through the shearing of mass ejection following the collapse. With a closer look, we find

The Younger Dryas (YD) cosmic impact hypothesis is gaining support due to the increasing amount of proxy evidence from 26 Younger Dryas Boundary sites that includes depositions of magnetic, silicate, and carbon spherules; high‐temperature meltglass and melt accretions; nanodiamonds, and Ir and Pt deposits, as well as evidence of major biomass burning and widespread extinctions in stratigraphic layers

The fractal basins of convergence (BoC) linked with the equilibrium points are explored in the (N + 1)− body ring problem under the effect of small perturbations in the Coriolis and centrifugal forces when the bodies are sources of radiation. The evolution of the positions and the stability of the libration points and the possible regions of motion are determined as the function of mass parameter,

We present 18,365 astrometric observations of 290 visual binaries obtained with the 26‐inch refractor of Pulkovo Observatory during 2014–2019. The separation between components is from 1″.3 to 37″ with a median value of 4″.8. For a single observation, the mean separation error is 0″.013, and the mean position angle error is 0∘.44/ρ, where ρ is an angular distance in arcseconds. We compare the observations

HD 69479/80 is a composite‐spectrum binary whose components are a late‐G giant and an early‐A dwarf. The orbit has a period of only 91 days (which seems short for a system containing a cool giant with a radius of ∼13 solar radii), and a very small, but probably significantly non‐zero, eccentricity. We separated the component spectra by a procedure of spectral subtraction, using a standard single giant

We present the spectral analysis with the Nuclear Spectroscopic Telescope Array (NuSTAR) of four isolated galaxies with active galactic nuclei selected from the 2MIG catalogue: NGC 5347, ESO 438‐009, MCG‐02‐09‐040, and IGR J11366‐6002. We also used the Swift/Burst Alert Telescope (BAT) data up to ∼150 keV for MCG 02‐09‐040, ESO 438‐009, and IGR J11366‐6002 as well as the Swift/XRT data in 0.3–10 keV

The recent measurement of a cutoff kmin in the fluctuation power spectrum P(k) of the cosmic microwave background may vitiate the possibility that slow‐roll inflation can simultaneously solve the horizon problem and account for the formation of structure via the growth of quantum fluctuations in the inflaton field. Instead, we show that kmin may be interpreted more successfully in the Rh = ct cosmology

Astrophysical images in the GeV band are challenging to analyze due to the strong contribution of the background and foreground astrophysical diffuse emission and relatively broad point spread function of modern space‐based instruments. In certain cases, even finding of point sources on the image becomes a non‐trivial task. We present a method for point sources extraction using a convolution neural

Historical star magnitudes from catalogs by Ptolemy (137 AD), al‐Sūfī (964), and Tycho Brahe (1602/27) are converted to the Johnson V‐mag scale and compared to modern‐day values from the HIPPARCOS catalog. The deviations (or “errors”) are tested for dependencies on three different observational influences. The relation between historical and modern magnitudes is found to be linear in all three catalogs

We present solar full‐disk observations that were recorded at the Einstein Tower during the years 1943–1991 (solar cycles 18–22). High‐school students from Potsdam and Berlin digitized more than 3,500 full‐disk images during 2–3‐week internships at Leibniz‐Institut für Astrophysik Potsdam (AIP). The digital images cover a 15 cm × 15 cm region on photographic plates, which were scanned at a resolution

Guided by the working hypothesis that the Schwabe cycle of solar activity is synchronized by the 11.07‐year alignment cycle of the tidally dominant planets Venus, Earth, and Jupiter, we reconsider the phase diagrams of sediment accumulation rates in Lake Holzmaar and of methanesulfonate data in the Greenland ice core Greenland Ice Sheet Project 2 (GISP2), which are available for the period 10000–9000 cal

In a well‐aimed search based on the recently published Gaia DR2 radial velocity data and performed with the robotic TIGRE telescope, we have discovered 19 bright (mV < 7.66 mag) spectroscopic binary stars. We present the radial velocity curves of five of these stars (HD 20656, HD 27259, HD 98812, HD 150600, HD 193082) with periods of P < 365 days. We determined their orbital parameters using the toolkit

Disentangling techniques are often needed to obtain the spectra of the individual components of binary or multiple systems. A thorough analysis of the shift‐and‐add algorithm of Marchenko et al, PASP, 1999;110:1416 reveals that, in many cases, the line fluxes are poorly reproduced, and spurious wings appear. The causes of these discrepancies are discussed, and a new disentangling package, QER20, is

High–precision trigonometric parallaxes, proper motions, and radial velocities of the Gaia DR2 catalog allow us to investigate the problem of open clusters rotation. Such a study could naturally be started with the clusters closest to the Sun, so we chose Praesepe as an object of our study. We selected 908 probable cluster members up to the apparent magnitude G = 19 mag based on their trigonometric

The aim of our work is to numerically explore the equilibrium points and the respective basins of convergence in the case of the circular restricted problem, where the two primaries are prolate. The coordinates of the libration points are derived by deploying the Newton–Raphson root method, while we also investigated the linear stability of the equilibrium points. Moreover, we also demonstrate the

This topical issue of Astronomische Nachrichten/Astronomical Notes contains a cross section of the articles that were presented at the 16th Potsdam Thinkshop, which was organized by the Leibniz Institute for Astrophysics Potsdam (AIP) and held on its campus in Babelsberg in September 2019. The title of the Thinkshop was “The rotation periods of cool stars: Measurements, uses, connections and prospects

Although photometric space‐based missions such as CoRoT or Kepler have yielded rotation measurements of many thousands of late‐type stars during the last decade, the rotational properties of the bulk of the G star population remain undetected by these missions. From the Sun (when viewed as a star), we know that rotation measurements in the ultraviolet are the most promising, or more general, measurements

The independent latitude stations (INDLS) catalog of proper motion in declination μδ for 682 bright Hipparcos (HIP) stars is presented. It is obtained in the Hipparcos reference frame, and only the Hipparcos mean position at epoch 1991.25 is used for INDLS data to calculate independent μδ (the HIP μδ values are not included in the INDLS data). Catalog comparisons were made in pairs for the four catalogs

We present a refined analysis of 15,038 Kepler main sequence light curves to determine the stellar rotation periods. The initial period estimates come from an autocorrelation function, as has been done before. We then measure the duration of every intensity dip in the light curve, expressed as fractions of the initial rotation period estimate. These dip duration distributions are subdivided into several

An original method of estimating the projected rotational velocity, vsini, and the macroturbulent velocity, vmac, of evolved M giant stars is presented. It is based on the use of spectrum synthesis and multiline analysis tools. The goal is to fit the mean line profile of observations with that of synthetic spectra. The method is applied to the red giant star RZ Ari, and the results vsini = 6.0 ± 0

With our robotic 1.2 m TIGRE telescope, we were able to obtain eight optical spectra with intermediate resolution (R ≈ 20,000) of the Nova V659 Sct during different phases of its outburst. We present a list of the lines found in the Nova spectra. The most common features are H I, O I, Na I, Fe II, and Ca II. Studying the spectral evolution of the strong features, we found that the absorption features

Blazars represent the dominant population of the extragalactic γ‐ray sources in the universe. These sources exhibit some characteristic properties such as strong and nonthermal continuum emission over the entire electromagnetic spectrum, from radio to Tera electron Volts (TeV) γ‐rays, with rapid variability on all timescales. The emission at radio and optical wavelengths is highly polarized with significant

Photometric surveys of open clusters have produced extensive measurements of rotation periods on Sun‐like stars of different ages. In particular, observations of intermediate age clusters, such as the Pleiades and M34, indicate a brief episode of rapid deceleration of stellar rotation at Rossby numbers between 0.1 and 0.3. I used those results to obtain new insights into the long‐term evolution of

We present the results of our spectroscopic monitoring observations of the late O‐type runaway stars AE Aur and ι Ori, carried out between September 2016 and May 2018 using the Échelle spectrograph FLECHAS at the University Observatory Jena. For both stars, we obtained current radial velocity (RV) measurements with better precision than before. These results can be used for further advanced calculations

We present imaging polarimetry observations of the recently discovered type I superluminous supernova 2020ank, in order to use (a)symmetry of the ejecta and SN photosphere that manifest themselves in the supernova lights as a probe of its explosion mechanism and investigate the energy sources that power the superluminous supernovae behind the scene. We have obtained linear imaging polarimetry in the

Karl‐Heinz Rädler died on the 9th of February 2020 at his home near Potsdam at the age of 85 years. He is known for his path‐breaking contributions to the development of cosmic dynamo theory. Together with Max Steenbeck and Fritz Krause, he presented a rigorous derivation of the α effect in 1966. A few years later, after their work became known in the West, many scientists around the globe applied

Photometric and spectral observations of the W UMa binaries FI Lyn, UV Lyn, and NSVS 781878 with periods of around 9.5–10 hr were carried out in order to determine their global parameters by simultaneous light curve and radial velocity curve solutions. We found that the three targets have shallow‐contact configurations with close in mass and radius components. UV Lyn is of W‐subtype, NSVS 781878 is

In a recent discussion of the Maunder Minimum, two sunspot observations by Chinese court astronomers on February 15, 1900 and January 30, 1911 (±1 day) – presumably made with the unaided eye – were considered false detections because the spot areas of the largest spot on those days (±1 day) as recorded by the Royal Greenwich Observatory, would be too small for naked‐eye detection, namely 11 and 13

In this paper, we investigate radio properties of active galaxies taken from the reference [Véron‐Cetty & Véron (2010)] catalog. The galaxies are limited to magnitudes in the range of 12m − 19m. We have cross‐correlated the list with radio catalogs and selected those galaxies that have data on six or more radio fluxes at different wavelengths. As a result, we have 198 galaxies that satisfy these conditions

Studies of the rotation–activity relation of late‐type stars are essential to enhance our understanding of stellar dynamos and angular momentum evolution. We study the rotation–activity relation with K2 for M dwarfs, where it is especially poorly understood. We analyzed the light curves of all bright and nearby M dwarfs form the Superblink proper motion catalog that were in the K2 field of view. Using

We present the results of a short observational program of asteroid 6478 Gault using of V and R Johnson filters realized at the Kyiv Comet Station during January to April 2019. Color indices and distribution of brightness in the comet‐like tail were calculated. We conducted a comparative analysis of circumstances of the asteroid 6478 Gault activity with others morphologically similar active main‐belt

In the present paper, an effort to generalize the restricted problem of 2 + 2 bodies has been made by considering the primary bodies m1 and m2 to be a point mass and straight segment of length 2l, respectively. The motion of the two infinitesimal bodies mi, i = 3, 4 has been investigated, in which each mi, i = 3, 4 is moving in the gravitational field of mj, j = 1, 2, 3, 4 with i ≠ j. For the present

In the case of single stars, larger stellar luminosities always entail larger habitable zones (HZs). If the stellar luminosity is increased, the HZs are established at larger stellar distances, and their widths are broader. However, studies have shown that this behavior is not necessarily the case for P‐type HZs of binary systems. In some of those systems, the width of the circumbinary HZ is smaller

We present relative astrometric and photometric measurements of visual binaries made in 2009–2010 with the 76‐cm refractor of Côte d'Azur Observatory and a pair of sensitive EMCCD ANDOR cameras. Our observing list includes optical pairs and binaries whose orbital motion is still uncertain. Three different techniques were used for obtaining measurements: Lucky Imaging, Speckle Interferometry, and the

The Gaia Data Release 2 (DR2) supplied a catalog of 147,644 late‐type stars for which the analysis of the G‐band photometric time series allowed the detection of the rotation period and an estimate of the magnetic activity level. The Gaia DR3 will be based on photometric time series spanning a longer time interval and will allow the detection and characterization of about 1 million stars with magnetic

We present the networks of planar symmetric periodic orbits in a single barred galaxy model. More specifically, we determine how the numerical value of the bar's semimajor axis affects not only the positions but also the linear stability of the periodic solutions. The atlas of the periodic orbits, with multiplicity up to 10, is presented on the (x, E) plane so as to be able to understand the importance

The aim of this paper is to analyze and shed light on the potential relations between two bodies of finite dimensions and different shapes. After explaining the properties of different shaped bodies, we analyze the gravitational potential between an irregular body and a point mass, followed by the potential relation between two irregular bodies with discussion of its different properties. We also explore

We present time‐resolved photometry of the cataclysmic variable PTF1J2224+17 obtained during four nights in October 2018 and January 2019 from Inastars observatory. The object is variable on a period of 103.82 min. Archival Catalina Real‐Time Transient Survey (CRTS), Palomar Transient Factory, and Zwicky Transient Facility‐data show frequent changes between high and low states. Based on its photometric

Solar twins are stars with a mass and chemical composition similar to the Sun; therefore, they follow about the same evolution and can be used to study the past and future of the Sun. I review the evolution of lithium and beryllium in solar‐mass solar‐metallicity main sequence stars, using a differential spectroscopic analysis of solar twins relative to the Sun, allowing precise determination of stellar

SMILE (Solar wind Magnetosphere Ionosphere Link Explorer) is a space mission which aims to measure Earth's global system responses to solar wind and geomagnetic variations with innovative instrumentation, for example, wide–field X‐ray telescope of Lobster–Eye type, on board. It is a collaborative project of the European Space Agency and the Chinese Academy of Sciences. The SMILE international consortium

The recent status of the European Space Agency's (ESA) THESEUS (Transient High‐Energy Sources and Early Universe Surveyor) project and the recent and expected Czech participation in this project are briefly presented and discussed. THESEUS is a mission concept proposed in response to the ESA's call for medium‐size mission (M5) within the Cosmic Vision Programme and selected by ESA on May 7, 2018, to

A summary of the long‐term, 1974–2018, measurements of the line‐of‐sight velocity of the solar photosphere, performed at the Crimean Astrophysical Observatory, is presented. The work shows that the Sun is pulsating with two periods: P0 = 9,600.606(12) s and P1 = 9,597.924(13) s. The new measurements, 1996–2018, confirm the remarkable phase stability of the second period. The true origin of both pulsations

In our previous work in Xiao et al. (SCPMA, 2019, 62, 129811), we suggested that six superluminal sources could be γ‐ray candidates, and in fact, five of them have been confirmed in the fourth Fermi‐LAT source catalog (4FGL). In this work, based on the 4FGL, we report a sample of 229 Fermi detected superluminal sources (FDSs), including 40 new FDSs and 62 non‐FDSs. Thus, we believe that all superluminal

The aim of this paper is to unveil, by means of self‐organizing maps (SOMs), the connections between intrinsic properties of radio quasars, namely redshift (z), luminosity (P), continuum slope (α), and parameters characterizing radio morphology of the host galaxy: observed linear size and bending. The strong luminosity–redshift correlation established by a prior traditional principal component analysis

We analyzed the optical photometric data of short‐term variability (flickering) of the accreting white dwarf in the jet‐ejecting symbiotic star MWC 560. The observations were obtained on 17 nights during the period November 2011 to October 2019. The color‐magnitude diagram shows that the hot component of the system becomes redder as it gets brighter. For the flickering source, we find that it has color

The ability of digital sky surveys to collect and store very large amounts of data provides completely new ways to study the local universe. Perhaps one of the most provocative observations reported with such tools is the asymmetry between galaxies with clockwise and counterclockwise spin patterns. Here, I use ∼1.7 × 105 spiral galaxies from Sloan Digital Sky Survey (SDSS) and sort them by their spin