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, v sini , and the macroturbulent velocity, v mac, 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 v sini  = 6.0 ± 0

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

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

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

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

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

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 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 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

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

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 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

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

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

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

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

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: P 0 = 9,600.606(12) s and P 1 = 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

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

Supernova remnants (SNRs) are the outcome of supernovae (SNe, either core collapse or thermonuclear). The remnant results from the interaction between the stellar ejecta and the ambient medium around the progenitor star. Young SNRs are characterized by strong shocks that heat and ionize the gas, generate magneto‐hydrodynamic turbulence, and accelerate particles to relativistic energies. They radiate

Presence of recombining (overionized) plasma in several supernova remnants (SNRs), first suggested by ASCA observations, was anchored by the detection of enhanced radiative recombination continua in Suzaku spectra of the SNRs IC 443 and W49B. This discovery was surprising, because X‐ray‐emitting SNRs were thought to have ionizing plasmas in general. Since then, similar spectral features have been detected

Supernova remnants (SNRs) are the aftermath of stellar explosions, which inject large amounts of energy into the interstellar medium (ISM), carving out new structures and transferring kinetic energy to the ISM. They also act as recycling centers, which return elements processed in stars to the ISM, and cosmic particle accelerators. The evolution of SNRs can be best studied in soft X‐ray line and continuum

We analyze the X‐ray emission from the supernova remnant DEM L71 using the smoothed particle inference (SPI) technique. The high Fe abundance found appears to confirm the Type Ia origin. Our method allows the separation of the material ejected in the supernova explosion from the material swept up by the supernova shock wave. We are able to calculate the total mass of this swept‐up material to be about

We investigate the broadband emission properties of the pulsar wind nebula (PWN) 3C 58 using a spectral energy distribution (SED) model. We attempt to match simultaneously the broadband SED and spatial variations of X‐ray emission in the PWN. We further use the model to explain a possible far‐IR feature of which a hint was recently suggested in 3C 58: a small bump at ∼1011 GHz in the PLANCK and Herschel

The hot circum‐galactic medium (CGM) represents the hot gas distributed beyond the stellar content of the galaxies while typically within their dark matter halos. It serves as a depository of energy and metal‐enriched materials from galactic feedback and a reservoir from which the galaxy acquires fuels to form stars. It thus plays a critical role in the coevolution of galaxies and their environments

Hot plasma is the dominant phase of the interstellar medium of early‐type galaxies. It can originate from stellar mass losses, residual gas from the formation epoch, and accretion from outside the galaxies. Its evolution is linked to the dynamical structure of the host galaxy, to the supernova and active galactic nuclei (AGN) feedback, and to (late‐epoch) star formation in a way that has yet to be

The Atomic Database project (AtomDB) atomic database provides access to a curated collection of atomic data, along with tools that convert this data into emissivities used in many analysis tools. We present the outline of some of the tools now available for accessing AtomDB using the new Python interface, developed to handle the larger datasets that exist since the release of version 3 in 2016. We

Charge exchange (CX) is a semi‐resonant recombination process that can lead to spectral line emission in the X‐ray band. It occurs in nearly any environment where hot plasma and cold gas interact: in the solar system, in comets and planetary atmospheres, and likely astrophysically, in, for example, supernova remnants and galaxy clusters. It also contributes to the soft X‐ray background. Accurate spectral

Accurate chemical abundance measurements of X‐ray‐emitting atmospheres pervading massive galaxies, galaxy groups, and clusters provide essential information on the star formation and chemical enrichment histories of these large‐scale structures. Although the collisionally ionized nature of the intracluster medium (ICM) makes these abundance measurements relatively easy, the underlying spectral models

We present the constraints on the helium abundance in 12 X‐ray‐luminous galaxy clusters that have been mapped in their X‐ray and Sunyaev–Zeldovich (SZ) signals out to R200 for the XMM‐Newton Cluster Outskirts Project (X‐COP). The unprecedented precision available for the estimate of H0 allows us to investigate how much the reconstructed X‐ray and SZ signals are consistent with the expected ratio x

The intracluster medium (ICM) contains the vast majority of the baryonic matter in galaxy clusters and is heated to X‐ray radiating temperatures. X‐ray spectroscopy is therefore a key to understanding both the morphology and the dynamics of galaxy clusters. Here we recall crucial evolutionary problems of galaxy clusters unveiled by 19 years of high‐resolution X‐ray spectroscopy with the reflection

The properties (temperature, density, chemical composition, velocity) of hot astrophysical plasma and the physical processes affecting them (heating/cooling, turbulence, shocks, acceleration) can be probed by high‐resolution X‐ray spectroscopy, to be complemented by high‐spatial‐resolution imaging. The paper presents the status of the European Space Agency's Advanced Telescope for High Energy Astrophysics

Does the Sun always rotate correctly? On the basis of the measurements of its mean magnetic field (more than 27 thousand daily values, obtained by seven observatories during 1968–2018) and resonance relations of the solar system, the sidereal spin period of the Sun as a star is determined as 25.165(6) days and that of the solar equator as 25.081(7) days. After 1993, however, a remarkable violation

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

We perform near‐infrared photometry of a large sample of 49 superthin edge‐on galaxies. These galaxies are selected based on optical photometry because of high radial‐to‐vertical scale ratio in their stellar disks. The near infrared (NIR) H and K observations were conducted with the cryogenic‐cooled camera ASTRONIRCAM on the 2.5 m telescope at the Caucasus Mountain Observatory of Lomonosov Moscow State

Optical surveys, such as the MACHO project, often uncover variable stars whose classification requires follow‐up observations by other instruments. We performed X‐ray spectroscopy and photometry of the unusual variable star MACHO 311.37557.169 with XMM‐Newton in April 2018, supplemented by archival X‐ray and optical spectrographic data. The star has a bolometric X‐ray luminosity of about 1 × 1032 erg s−1 cm−2

The present problem is devoted to the special case of restricted problem of three bodies, always referred as the Copenhagen problem when we consider the primaries of equal masses. In this manuscript, we have considered the third body of infinitesimal mass as variable and moreover, instead of taking only Newtonian potential and forces, a quasi‐homogeneous potential produced by the main primaries has

The Next Generation Transit Survey (NGTS) is a photometric survey for transiting exoplanets, consisting of 12 identical 0.2‐m telescopes. We report a measurement of the transit of HD 106315 c using a novel observing mode in which multiple NGTS telescopes observed the same target, with the aim of increasing the signal‐to‐noise ratio. Combining the data allows the robust detection of the transit, which

Machine learning techniques have been widely used in attempts to forecast several solar datasets such as the sunspot count, the sunspot area, flare activity, solar wind magnitude, and solar storms/coronal mass ejections (CMEs) activity. Most of these approaches employ supervised machine learning algorithms which are, in general, very data hungry. This hampers the attempts to forecast some of these

Follow‐up imaging observations of the first detected interstellar comet 2I/Borisov are presented, which were carried out with the Schmidt‐Teleskop‐Kamera at the University Observatory Jena in 11 observing epochs in October and November 2019. The orbital solution of the comet, derived from the obtained astrometric measurements, confirms its highly eccentric (e  = 3.3570 ± 0.0006) and inclined (i  = 44

Based on the shell and pair effects and the decay energy, we investigate the comparative half‐lives of β −‐decay for some iron group nuclei and mainly discuss the electron energy, beta decay threshold energy, and the antineutrino energy losses by β −‐decay of several typical iron isotopes in the presence of strong electron screening (SES) and in the framework of linear response theory. Our main findings

Space debris larger than 1 cm can damage space instruments and impact Earth. The low‐Earth orbits (at heights smaller than 2,000 km) and orbits near the geostationary‐Earth orbit (at 35,786 km height) are especially endangered because most satellites orbit at these latitudes. With current technology, space debris smaller than 10 cm cannot be tracked. Smaller space debris fragments burn up and evaporate

It is shown how the large‐scale inhomogeneous distribution of chemical elements in the primordial medium contributes to temperature fluctuations of the cosmic microwave background radiation (CMB). The magnitude of the chemical anisotropy of the CMB, which is sensitive to the absolute and relative abundance of chemical elements at the time of decoupling, is compared with the primary Sachs‐Wolfe anisotropy

We analyze emission line properties and their correlations for 18,043 type 1 active galactic nucleus (AGN) in the range of 0.02 ≤ z  ≤ 0.8, based on Sloan Digital Sky Survey Data Release 14 data. We complement the data with photometric measurements from ROSAT, GALEX, 2MASS, and FIRST. We find the following: (a) The average correlation between luminosity of [O III] and AGN luminosity is stronger than

The results of the analysis of the single‐color (B) observations undertaken at the Stefanion Observatory for the red dwarf star AD Leo at any stage of the stellar activity (quiescence, weak flares, strong flares) indicate that (a) transient high‐frequency oscillations occur during the flare event and during the quiet‐star phase as well, and (b) the observed frequencies range between 0.0005 Hz (period