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  • Formation of spiral structure from the violent relaxation of self‐gravitating disks
    Astron. Nachr. (IF 1.064) Pub Date : 2020-10-21
    Tirawut Worrakitpoonpon

    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

    更新日期:2020-10-22
  • A resolution of the trans‐Planckian problem in the Rh = ct universe
    Astron. Nachr. (IF 1.064) Pub Date : 2020-10-18
    Fulvio Melia

    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

    更新日期:2020-10-19
  • The HD 217107 planetary system: Twenty years of radial velocity measurements
    Astron. Nachr. (IF 1.064) Pub Date : 2020-10-11
    Mark R. Giovinazzi; Cullen H. Blake; Jason D. Eastman; Jason Wright; Nate McCrady; Rob Wittenmyer; John A. Johnson; Peter Plavchan; David H. Sliski; Maurice L. Wilson; Samson A. Johnson; Jonathan Horner; Stephen R. Kane; Audrey Houghton; Juliana García‐Mejía; Joseph P. Glaser

    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

    更新日期:2020-10-12
  • Isolated AGNs NGC 5347, ESO 438‐009, MCG‐02‐04‐090, and J11366‐6002: Swift and NuSTAR joined view1
    Astron. Nachr. (IF 1.064) Pub Date : 2020-09-29
    Anatoliy A. Vasylenko; Irina B. Vavilova; Nadiia G. Pulatova

    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

    更新日期:2020-09-30
  • Solar observatory Einstein Tower: Data release of the digitized solar full‐disk photographic plate archive
    Astron. Nachr. (IF 1.064) Pub Date : 2020-07-26
    Partha S. Pal; Meetu Verma; Jürgen Rendtel; Sergio Javier González Manrique; Harry Enke; Carsten Denker

    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

    更新日期:2020-09-28
  • Phase coherence and phase jumps in the Schwabe cycle
    Astron. Nachr. (IF 1.064) Pub Date : 2020-08-31
    Frank Stefani; Jürg Beer; André Giesecke; Timo Gloaguen; Martin Seilmayer; Rodion Stepanov; Tom Weier

    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

    更新日期:2020-09-28
  • Bright spectroscopic binaries: I. Orbital parameters of five systems with periods of P < 365 days
    Astron. Nachr. (IF 1.064) Pub Date : 2020-08-23
    Dennis Jack; Missael Alejandro Hernández Huerta; Klaus‐Peter Schröder

    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

    更新日期:2020-09-28
  • The massive binary system 9 Sgr revisited: New insights into disentangling methods
    Astron. Nachr. (IF 1.064) Pub Date : 2020-07-27
    Edwin A. Quintero; Philippe Eenens; Gregor Rauw

    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

    更新日期:2020-09-28
  • Rotation of open clusters based on Gaia data. Praesepe
    Astron. Nachr. (IF 1.064) Pub Date : 2020-09-13
    Alexander V. Loktin; Alexander A. Popov

    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

    更新日期:2020-09-28
  • The study of the fractal basins of convergence linked with equilibrium points in the perturbed (N + 1)‐body ring problem
    Astron. Nachr. (IF 1.064) Pub Date : 2020-09-21
    Md Sanam Suraj; Rajiv Aggarwal; Amit Mittal; Om Prakash Meena; Md Chand Asique

    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,

    更新日期:2020-09-22
  • Main Belt asteroid as a Possible Younger Dryas impactor
    Astron. Nachr. (IF 1.064) Pub Date : 2020-09-20
    Maxim Usatov

    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

    更新日期:2020-09-21
  • Accuracy of magnitudes in pre‐telescopic star catalogs
    Astron. Nachr. (IF 1.064) Pub Date : 2020-09-14
    Philipp Protte; Susanne M. Hoffmann

    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

    更新日期:2020-09-15
  • Astrometric observations of visual binaries using 26‐inch refractor at Pulkovo Observatory during 2014–2019
    Astron. Nachr. (IF 1.064) Pub Date : 2020-09-13
    Igor Izmailov; Aleksey Rublevsky; Arina Apetyan

    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

    更新日期:2020-09-14
  • A study of neural networks point source extraction on simulated Fermi/LAT telescope images
    Astron. Nachr. (IF 1.064) Pub Date : 2020-09-02
    Drozdova Mariia; Broilovskiy Anton; Ustyuzhanin Andrey; Malyshev Denys

    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

    更新日期:2020-09-03
  • Convergence properties of equilibria in the restricted three‐body problem with prolate primaries
    Astron. Nachr. (IF 1.064) Pub Date : 2020-09-01
    Tareq Saeed; Wei Chen; Euaggelos E. Zotos

    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

    更新日期:2020-09-02
  • 16th Potsdam Thinkshop: The rotation periods of cool stars: Measurements, uses, connections and prospects
    Astron. Nachr. (IF 1.064) Pub Date : 2020-08-27
    Sydney A. Barnes; Matthias Steffen; Klaus G. Strassmeier

    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

    更新日期:2020-08-28
  • Rotation of solar‐like stars in the immediate solar neighborhood
    Astron. Nachr. (IF 1.064) Pub Date : 2020-08-23
    Jürgen H. M. M. Schmitt, Marco Mittag

    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

    更新日期:2020-08-23
  • Latitude observations of the last century to obtain accurate independent latitude stations (INDLS) catalog of μδ for 682 Hipparcos stars and comparison with Gaia DR2
    Astron. Nachr. (IF 1.064) Pub Date : 2020-08-17
    Goran Damljanović

    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

    更新日期:2020-08-18
  • Double‐dipping to refine stellar rotation periods
    Astron. Nachr. (IF 1.064) Pub Date : 2020-08-03
    Joanne Tan, Gibor Basri

    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

    更新日期:2020-08-03
  • Determining rotational and macroturbulent velocities of cool magnetic giant stars
    Astron. Nachr. (IF 1.064) Pub Date : 2020-07-27
    Stefan Georgiev, Agnès Lèbre, Eric Josselin, Renada Konstantinova‐Antova, Julien Morin

    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

    更新日期:2020-07-27
  • Time series of optical spectra of Nova V659 Sct
    Astron. Nachr. (IF 1.064) Pub Date : 2020-07-20
    Dennis Jack; Klaus‐Peter Schröder; Philippe Eenens; Uwe Wolter; José Nicolás González‐Pérez; Jürgen H. M. M. Schmitt; Peter H. Hauschildt

    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

    更新日期:2020-07-21
  • Characterization of variability in blazar light curves
    Astron. Nachr. (IF 1.064) Pub Date : 2020-07-16
    Krishna K. Singh; Peter J. Meintjes

    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

    更新日期:2020-07-16
  • Rossby number and chromospheric activity of solar mass stars
    Astron. Nachr. (IF 1.064) Pub Date : 2020-07-14
    Philippe Gondoin

    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

    更新日期:2020-07-14
  • Radial velocity measurements of the runaway stars AE Aur and ι Ori
    Astron. Nachr. (IF 1.064) Pub Date : 2020-07-13
    Therese Heyne; M. Mugrauer; R. Bischoff; D. Wagner; R. Neuhäuser; S. M. Hoffmann; O. Lux

    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

    更新日期:2020-07-13
  • Early optical imaging polarimetry of type I superluminous supernova 2020ank
    Astron. Nachr. (IF 1.064) Pub Date : 2020-07-13
    Chien‐Hsiu Lee

    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

    更新日期:2020-07-13
  • Karl‐Heinz Rädler (1935–2020)
    Astron. Nachr. (IF 1.064) Pub Date : 2020-07-08
    Axel Brandenburg; Günther Rüdiger; Guenther Ruediger

    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

    更新日期:2020-07-09
  • Global parameters of the W UMa stars FI Lyn, UV Lyn, and NSVS 781878
    Astron. Nachr. (IF 1.064) Pub Date : 2020-07-08
    Diana P. Kjurkchieva, Velimir A. Popov, Dragomir V. Marchev, Ivanka K. Stateva

    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

    更新日期:2020-07-08
  • Comparison of telescopic and naked‐eye sunspots for the very small spots on February 15, 1900 and January 30, 1911
    Astron. Nachr. (IF 1.064) Pub Date : 2020-07-02
    Ralph Neuhäuser, Michael Geymeier, Rainer Arlt, Jesse Chapman

    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

    更新日期:2020-07-02
  • The nature of active galaxies based on their radio properties
    Astron. Nachr. (IF 1.064) Pub Date : 2020-06-28
    Hayk V. Abrahamyan

    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

    更新日期:2020-06-28
  • The rotation–activity relation of M dwarfs: From K2 to TESS and PLATO
    Astron. Nachr. (IF 1.064) Pub Date : 2020-06-25
    Stefanie Raetz, Beate Stelzer, Alexander Scholz

    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

    更新日期:2020-06-25
  • Astronomische Nachrichten—Broadband photometry of asteroid 6478 Gault: Activity and morphology
    Astron. Nachr. (IF 1.064) Pub Date : 2020-06-24
    Serhii Borysenko, Alexander Baransky, Andrii Simon, Volodymyr Vasylenko

    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

    更新日期:2020-06-24
  • An insight on the restricted problem of 2 + 2 bodies with straight segment
    Astron. Nachr. (IF 1.064) Pub Date : 2020-06-22
    Dinesh Kumar; Rajiv Aggarwal; Bhavneet Kaur

    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

    更新日期:2020-06-22
  • When more is less: The P‐type binary habitability paradox
    Astron. Nachr. (IF 1.064) Pub Date : 2020-06-22
    Manfred Cuntz, Zhaopeng Wang

    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

    更新日期:2020-06-22
  • Measurements of visual binaries with EMCCD cameras and the Nice 76‐cm refractor in 2009–2010
    Astron. Nachr. (IF 1.064) Pub Date : 2020-06-17
    René Gili, Jean‐Louis Prieur, Jean‐Pierre Rivet, Marco Scardia, Luigi Pansecchi, Robert W. Argyle, Josefina F. Ling, Luca Piccotti, Eric Aristidi, Laurent Koechlin, Daniel Bonneau, Luca Maccarini

    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

    更新日期:2020-06-17
  • Detection and characterization of stellar magnetic activity with Gaia
    Astron. Nachr. (IF 1.064) Pub Date : 2020-06-17
    Elisa Distefano, Alessandro Lanzafame

    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

    更新日期:2020-06-17
  • Networks of planar symmetric periodic orbits in a barred galaxy model
    Astron. Nachr. (IF 1.064) Pub Date : 2020-06-16
    Euaggelos E. Zotos; Christof Jung; Konstandinos E. Papadakis; Tareq Saeed

    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

    更新日期:2020-06-16
  • Gravitational potential formulae between two bodies with finite dimensions
    Astron. Nachr. (IF 1.064) Pub Date : 2020-06-02
    Abdullah A. Ansari; Elbaz I. Abouelmagd

    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

    更新日期:2020-06-02
  • PTF1J2224+17: A short‐period, high‐field polar
    Astron. Nachr. (IF 1.064) Pub Date : 2020-06-01
    Axel D. Schwope, Bernd D. Thinius

    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

    更新日期:2020-06-01
  • Lithium and beryllium in solar twins
    Astron. Nachr. (IF 1.064) Pub Date : 2020-06-01
    Jorge Meléndez

    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

    更新日期:2020-06-01
  • European Space Agency SMILE and Czech participation
    Astron. Nachr. (IF 1.064) Pub Date : 2020-05-26
    Rene Hudec, Graziella Branduardi‐Raymont, Steven Sembay, Vojtech Simon

    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

    更新日期:2020-05-26
  • ESA THESEUS and Czech participation
    Astron. Nachr. (IF 1.064) Pub Date : 2020-05-26
    Rene Hudec, Lorenzo Amati, Filippo Frontera, Enrico Bozzo, Paul T. O'Brien, Diego Goetz, Vojtech Simon

    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

    更新日期:2020-05-26
  • Oscillations of solar photosphere: 45 years of observations
    Astron. Nachr. (IF 1.064) Pub Date : 2020-05-25
    Valery A. Kotov; Vasilij I. Haneychuk

    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

    更新日期:2020-05-25
  • Further evidence of superluminal active galactic nuclei as γ‐ray sources
    Astron. Nachr. (IF 1.064) Pub Date : 2020-05-18
    Hubing Xiao, Junhui Fan, Riccardo Rando, Jingtian Zhu, Liangjun Hu

    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

    更新日期:2020-05-18
  • Unsupervised classification of the intrinsic and morphological properties of quasars through self‐organizing maps
    Astron. Nachr. (IF 1.064) Pub Date : 2020-04-28
    Aysel Karafistan, Eser Gemikonakli

    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

    更新日期:2020-04-28
  • Flickering of the jet‐ejecting symbiotic star MWC 560
    Astron. Nachr. (IF 1.064) Pub Date : 2020-04-22
    R. K. Zamanov, S. Boeva, K. A. Stoyanov, G. Latev, B. Spassov, A. Kurtenkov, G. Nikolov

    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

    更新日期:2020-04-22
  • Large‐scale asymmetry between clockwise and counterclockwise galaxies revisited
    Astron. Nachr. (IF 1.064) Pub Date : 2020-04-21
    Lior Shamir

    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

    更新日期:2020-04-21
  • Near‐infrared photometry of superthin edge‐on galaxies
    Astron. Nachr. (IF 1.064) Pub Date : 2020-04-19
    Dmitry Bizyaev, Andrey Tatarnikov, Nikolai Shatsky, Aurik Najip, Marina Birlak, Olga Voziakova

    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

    更新日期:2020-04-19
  • MACHO 311.37557.169: A VY Scl star
    Astron. Nachr. (IF 1.064) Pub Date : 2020-04-14
    Hauke Wörpel, Axel D. Schwope, Iris Traulsen, Michael J. I. Brown

    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

    更新日期:2020-04-14
  • Analysis of Copenhagen problem with a repulsive quasi‐homogeneous Manev‐type potential within the frame of variable mass
    Astron. Nachr. (IF 1.064) Pub Date : 2020-04-12
    Md Sanam Suraj, Amit Mittal, Charanpreet Kaur, Rajiv Aggarwal

    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

    更新日期:2020-04-12
  • Shallow transit follow‐up from Next‐Generation Transit Survey: Simultaneous observations of HD 106315 with 11 identical telescopes
    Astron. Nachr. (IF 1.064) Pub Date : 2020-04-12
    Alexis M. S. Smith, Philipp Eigmüller, Ramanathan Gurumoorthy, Szilárd Csizmadia, Daniel Bayliss, Matthew R. Burleigh, Juan Cabrera, Sarah L. Casewell, Anders Erikson, Michael R. Goad, Andrew Grange, James S. Jenkins, Don Pollacco, Heike Rauer, Liam Raynard, Stéphane Udry, Richard G. West, Peter J. Wheatley

    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

    更新日期:2020-04-12
  • Transfer learning in spatial–temporal forecasting of the solar magnetic field
    Astron. Nachr. (IF 1.064) Pub Date : 2020-03-30
    Eurico Covas

    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

    更新日期:2020-03-30
  • Follow‐up imaging observations of comet 2I/Borisov
    Astron. Nachr. (IF 1.064) Pub Date : 2020-03-26
    Markus Mugrauer, Richard Bischoff, Wolfgang Stenglein, Julius Trautmann, Baghdasar Baghdasaryan, Saskia Schlagenhauf

    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

    更新日期:2020-03-26
  • Supernova antineutrino energy losses of 59Co, 56Co, 56Ni, and 56Fe by β−‐decay in strongly screened plasma
    Astron. Nachr. (IF 1.064) Pub Date : 2020-03-22
    Jing Jing Liu, Dong Mei Liu

    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

    更新日期:2020-03-22
  • Rotation anomaly of the Sun
    Astron. Nachr. (IF 1.064) Pub Date : 2020-03-18
    Valery A. Kotov

    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

    更新日期:2020-03-18
  • Recombining plasma in supernova remnants: Discovery and progress in the last decade
    Astron. Nachr. (IF 1.064) Pub Date : 2020-03-17
    Hiroya Yamaguchi

    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

    更新日期:2020-03-17
  • How do atomic code uncertainties affect abundance measurements in the intracluster medium?
    Astron. Nachr. (IF 1.064) Pub Date : 2020-03-17
    François Mernier, Norbert Werner, Kiran Lakhchaura, Jelle de Plaa, Liyi Gu, Jelle S. Kaastra, Junjie Mao, Aurora Simionescu, Igone Urdampilleta

    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

    更新日期:2020-03-17
  • Dynamics of spherical space debris of different sizes falling to Earth
    Astron. Nachr. (IF 1.064) Pub Date : 2020-03-17
    Judit Slíz‐Balogh, Dániel Horváth, Róbert Szabó, Gábor Horváth

    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

    更新日期:2020-03-17
  • Chemical anisotropy of the cosmic microwave background radiation
    Astron. Nachr. (IF 1.064) Pub Date : 2020-03-15
    W. T. Chyla

    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

    更新日期:2020-03-15
  • Charge exchange, from the sky to the laboratory: A method to determine state‐selective cross‐sections for improved modeling
    Astron. Nachr. (IF 1.064) Pub Date : 2020-03-05
    Gabriele L. Betancourt‐Martinez, Renata S. Cumbee, Maurice A. Leutenegger

    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

    更新日期:2020-03-05
  • Lessons learned from 19 years of high‐resolution X‐ray spectroscopy of galaxy clusters with the reflection grating spectrometer on board XMM‐Newton
    Astron. Nachr. (IF 1.064) Pub Date : 2020-03-04
    Ciro Pinto, Andrew C. Fabian, Jeremy S. Sanders, Jelle de Plaa

    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

    更新日期:2020-03-04
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