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Results in Journal Astronomische Nachrichten: 48,220

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, Ashraf Tadross
Published: 7 May 2021
by Wiley
Astronomische Nachrichten; doi:10.1002/asna.202143848

Abstract:
The estimation of the main parameters of star clusters is significant in astrophysical studies. The most important aspect of using the Gaia DR2 survey lies in the positions, parallax, and proper motions of cluster stars with homogeneous photometry that make the membership probability determine with high accuracy. In this respect, depending on Gaia DR2 database, an analysis of the open star cluster Melotte 72 is taking place here. It is located at a distance of 2,345 ± 108 pc with an age of 1.0 ± 0.5 Gyr. In studying the radial density profile, the radius is found to be 5.0 ± 0.15 arcmin. The reddening, the luminosity and mass functions, the total mass of the cluster, and the galactic geometrical distances (X⊙, Y⊙, Z⊙), and the distance from the galactic center (Rg) have been estimated as well. Our study has shown a dynamical relaxation behavior of Melotte 72.
, Dagmar L. Neuhäuser
Published: 5 May 2021
by Wiley
Astronomische Nachrichten; doi:10.1002/asna.202113872

Abstract:
We critically discuss recent articles by S. Hoffmann and N. Vogt on historical novae and supernovae (SNe) as well as their list of “24 most promising events” “with rather high probability to be a nova” (Hoffmann et al., AN, 2020, 341, 79 (P3)). Their alleged positional accuracy of previously suggested historical nova/SN records is based on inhomogeneous datasets (Vogt et al.), but then used for the nova search in Hoffmann et al., AN, 2020, 341, 79 (P3). Their claim that previously only “point coordinates” for nova/SN candidates were published, is fabricated. Their estimate of expected nova detection rates is off by a factor of 10 due to mis‐calculation. They accept counterparts down to 4–7 mag at peak, which is against the consensus for the typical limit of naked‐eye discovery. When they discuss previously suggested identifications of historical novae, which they all doubt, they do not present new facts (Hoffmann, MNRAS, 2019, 490, 4194 (P2)). Their catalog of “24 most promising events” for novae (Hoffmann et al., AN, 2020, 341, 79 (P3)) neglects important recent literature (e.g. Pankenier et al., Archeoastronomy in East Asia, New York, Cambria, 2008 and Stephenson and Green, JHA, 2009, 40, 31), the claimed methods are not followed, etc. At least half of their short‐list candidates were and are to be considered comets. For many of the others, duration of more than one night and/or a precise position is missing and/or the sources were treated mistakenly. Two “highlights,” a fabricated SN AD 667–8 and a presumable recurrent nova in AD 891, are already rejected in detail in Neuhäuser et al., MNRAS, 2021a, 501, L1—in both cases, all evidence speaks in favor of comets. There remains only one reliable case, where close to one (possible) historically reported position, a nova shell was already found (AD 1437, Shara et al., Nature, 2017b, 548, 558). Since the proposed positional search areas are not justified due to unfounded textual interpretations (e.g. in fact comets), misunderstandings of historical Chinese astronomy (e.g. incorrect asterism), follow‐up observations cannot be recommended.
, Teeraparb Chantavat, Jenna Zunder
Published: 2 May 2021
by Wiley
Astronomische Nachrichten; doi:10.1002/asna.202113826

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, Abdullah A. Ansari
Published: 29 April 2021
by Wiley
Astronomische Nachrichten; doi:10.1002/asna.202113870

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, Mohsen Bigdeli
Published: 15 April 2021
by Wiley
Astronomische Nachrichten; doi:10.1002/asna.202113862

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, Varvara Vladimirovna Butkovskaya, Nikolai Fedorovich Pankov
Published: 29 March 2021
by Wiley
Astronomische Nachrichten; doi:10.1002/asna.202113858

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Published: 4 March 2021
by Wiley
Astronomische Nachrichten, Volume 342, pp 588-597; doi:10.1002/asna.202123869

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Published: 4 March 2021
by Wiley
Astronomische Nachrichten, Volume 342, pp 515-530; doi:10.1002/asna.202123873

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, Kiril A. Stoyanov, Josep Mart, Vladislav D. Marchev, Yanko M. Nikolov
Published: 4 March 2021
by Wiley
Astronomische Nachrichten, Volume 342, pp 531-537; doi:10.1002/asna.202123856

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Published: 1 March 2021
by Wiley
Astronomische Nachrichten, Volume 342; doi:10.1002/asna.202190003

Published: 1 March 2021
by Wiley
Astronomische Nachrichten, Volume 342, pp 479-484; doi:10.1002/asna.202190004

Published: 23 February 2021
by Wiley
Astronomische Nachrichten, Volume 342, pp 578-587; doi:10.1002/asna.202113868

Abstract:
Nowadays, publications in astrophysics are mainly published and read in digitized formats. Astrophysical publications in both research and in popular outreach often use colorful representations of stars to indicate various stellar types, that is, different spectral types or effective temperatures. Computer‐generated and computer‐displayed imagery has become an integral part of stellar astrophysics communication. There is, however, no astrophysically motivated standard color palette for illustrative representations of stars, and some stars are actually represented in misleading colors. We use precomputed PHOENIX and TLUSTY stellar model spectra and convolve them with the three standard color‐matching functions for human color perception between 360 and 830 nm. The color‐matching functions represent the three sets of receptors in the eye that respond to red, green, and blue light. For a grid of main‐sequence stars with effective temperatures between 2,300 and 55,000 K of different metallicities, we present the red–blue–green and hexadecimal color codes that can be used for digitized color representations of stars as if seen from space. We find significant deviations between the color codes of stars computed from stellar spectra and from a black body radiator of the same effective temperature. We illustrate the main sequence in the color wheel and demonstrate that there are no yellow, green, cyan, or purple stars. Red dwarf stars (spectral types M0V–M9V) actually look orange to the human eye. Old white dwarfs such as WD 1856 + 534, host to a newly discovered transiting giant planet candidate, appear pale orange to the human eye, not white. Our freely available software can be used to generate color codes for any input spectrum such as those from planets, galaxies, quasars, etc.
, Sergey A. Korotin, Dmitry V. Petrov, Dmitry B. Poklad, David E. Mkrtichian, Inwoo Han, Byeong‐Cheol Lee
Published: 14 February 2021
by Wiley
Astronomische Nachrichten, Volume 342, pp 497-514; doi:10.1002/asna.202113853

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Stefanos Tsiopelas,
Published: 31 January 2021
by Wiley
Astronomische Nachrichten, Volume 342, pp 332-336; doi:10.1002/asna.202113929

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Published: 31 January 2021
by Wiley
Astronomische Nachrichten, Volume 342, pp 277-282; doi:10.1002/asna.202113919

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, Karín Menéndez‐Delmestre
Published: 31 January 2021
by Wiley
Astronomische Nachrichten, Volume 342, pp 186-190; doi:10.1002/asna.202113902

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Milton Rojas Gamarra, Steven R. Gullberg, Mônica Estrázulas, Jorge Horvath,
Published: 28 January 2021
by Wiley
Astronomische Nachrichten, Volume 342, pp 31-38; doi:10.1002/asna.202113876

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, Anirban Bhattacharjee
Published: 28 January 2021
by Wiley
Astronomische Nachrichten, Volume 342, pp 142-146; doi:10.1002/asna.202113894

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Published: 28 January 2021
by Wiley
Astronomische Nachrichten, Volume 342, pp 176-181; doi:10.1002/asna.202113900

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, Gretel Quintero Angulo, Aurora Pérez Martínez, Hugo Pérez Rojas
Published: 28 January 2021
by Wiley
Astronomische Nachrichten, Volume 342, pp 110-114; doi:10.1002/asna.202113889

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, Fabio Da Silva Bortoli, Nadja S. Magalhaes
Published: 28 January 2021
by Wiley
Astronomische Nachrichten, Volume 342, pp 222-226; doi:10.1002/asna.202113908

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, Peter O. Hess, Gabriella Piccinelli, Mariana Vargas Magaña, Luis Arturo Ureña‐Lopez, Ricardo Gonzalez Felipe, Thomas Boller, Steven Gullberg
Published: 28 January 2021
by Wiley
Astronomische Nachrichten, Volume 342, pp 18-24; doi:10.1002/asna.202113874

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Fang‐Zhou Yan, , Wen‐Shen Yang, Ai‐Jun Dong
Published: 28 January 2021
by Wiley
Astronomische Nachrichten, Volume 342, pp 249-254; doi:10.1002/asna.202113913

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, Yurii I. Stozhkov
Published: 28 January 2021
by Wiley
Astronomische Nachrichten, Volume 342, pp 342-346; doi:10.1002/asna.202113931

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Published: 28 January 2021
by Wiley
Astronomische Nachrichten, Volume 342, pp 234-239; doi:10.1002/asna.202113910

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Andrei P. Igoshev,
Published: 27 January 2021
by Wiley
Astronomische Nachrichten, Volume 342, pp 216-221; doi:10.1002/asna.202113907

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, Mariana Vargas Magaña, Marcos Iram Toledo Ortiz, Brenda Izamar Tapia Benavides, Matias Rodriguez Otero, Beatriz Miroslava Sandoval Ramos
Published: 27 January 2021
by Wiley
Astronomische Nachrichten, Volume 342, pp 171-175; doi:10.1002/asna.202113899

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, Raúl Lizardo–Castro, Ulises Nucamendi
Published: 27 January 2021
by Wiley
Astronomische Nachrichten, Volume 342, pp 198-204; doi:10.1002/asna.202113904

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, Jurandi Leão, Manuel Castro, Flavio D'Amico
Published: 27 January 2021
by Wiley
Astronomische Nachrichten, Volume 342, pp 315-319; doi:10.1002/asna.202113926

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Yakov Istomin,
Published: 27 January 2021
by Wiley
Astronomische Nachrichten, Volume 342, pp 182-185; doi:10.1002/asna.202113901

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, Johannes Kirsch, Jürgen Struckmeier
Published: 26 January 2021
by Wiley
Astronomische Nachrichten, Volume 342, pp 81-88; doi:10.1002/asna.202113885

Abstract:
The cosmological implications of the Covariant Canonical Gauge Theory of Gravity (CCGG) are investigated. CCGG is a Palatini theory derived from first principles using the canonical transformation formalism in the covariant Hamiltonian formulation. The Einstein‐Hilbert theory is thereby extended by a quadratic Riemann‐Cartan term in the Lagrangian. Moreover, the requirement of covariant conservation of the stress‐energy tensor leads to necessary presence of torsion. In the Friedman universe that promotes the cosmological constant to a time‐dependent function, and gives rise to a geometrical correction with the EOS of dark radiation. The resulting cosmology, compatible with the ΛCDM parameter set, encompasses bounce and bang scenarios with graceful exits into the late dark energy era. Testing those scenarios against low‐z observations shows that CCGG is a viable theory.
, Dominik R. G. Schleicher, Siegfried Vanaverbeke, Ralf S. Klessen
Published: 26 January 2021
by Wiley
Astronomische Nachrichten, Volume 342, pp 157-163; doi:10.1002/asna.202113897

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, Christopher Layser
Published: 26 January 2021
by Wiley
Astronomische Nachrichten, Volume 342, pp 39-44; doi:10.1002/asna.202113877

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, Soumya Roy, Suchetana Chatterjee, NishikantA Khandai, Craig L. Sarazin, Tiziana Di Matteo
Published: 24 January 2021
by Wiley
Astronomische Nachrichten, Volume 342, pp 164-170; doi:10.1002/asna.202113898

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, Abdel Magied Diab, Sameh Shenawy, Eiman Abou El Dahab
Published: 24 January 2021
by Wiley
Astronomische Nachrichten, Volume 342, pp 54-57; doi:10.1002/asna.202113880

Abstract:
When minimal length uncertainty emerging from a generalized uncertainty principle (GUP) is thoughtfully implemented, it is of great interest to consider its impacts on gravitational Einstein field equations (gEFEs) and to try to assess consequential modifications in metric manifesting properties of quantum geometry due to quantum gravity. GUP takes into account the gravitational impacts on the noncommutation relations of length (distance) and momentum operators or time and energy operators and so on. On the other hand, gEFE relates classical geometry or general relativity gravity to the energy–momentum tensors, that is, proposing quantum equations of state. Despite the technical difficulties, we intend to insert GUP into the metric tensor so that the line element and the geodesic equation in flat and curved space are accordingly modified. The latter apparently encompasses acceleration, jerk, and snap (jounce) of a particle in the quasi‐quantized gravitational field. Finite higher orders of acceleration apparently manifest phenomena such as accelerating expansion and transitions between different radii of curvature and so on.
, Carlos Frajuca, Nadja S. Magalhaes
Published: 24 January 2021
by Wiley
Astronomische Nachrichten, Volume 342, pp 123-127; doi:10.1002/asna.202113891

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Daniela Pérez, Santiago E. Perez Bergliaffa, Gustavo E. Romero
Published: 24 January 2021
by Wiley
Astronomische Nachrichten, Volume 342, pp 69-74; doi:10.1002/asna.202113883

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Lien Rodríguez‐López, , Lisdelys González‐Rodríguez, , Jorge Horvath
Published: 24 January 2021
by Wiley
Astronomische Nachrichten, Volume 342, pp 45-48; doi:10.1002/asna.202113878

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, Amanda O. Harrison, Dimitrios Giannios
Published: 21 January 2021
by Wiley
Astronomische Nachrichten, Volume 342, pp 147-152; doi:10.1002/asna.202113895

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Published: 21 January 2021
by Wiley
Astronomische Nachrichten, Volume 342, pp 63-68; doi:10.1002/asna.202113882

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, Selçuk Bilir, Tansel Ak, Burcu Akbulut, Remziye Canbay, Timothy Banks, Ernst Paunzen, Serap Ak, Zahide Funda Bostancı
Published: 21 January 2021
by Wiley
Astronomische Nachrichten, Volume 342, pp 538-552; doi:10.1002/asna.202113837

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, Sanjay Mandal, Simran Arora
Published: 21 January 2021
by Wiley
Astronomische Nachrichten, Volume 342, pp 89-95; doi:10.1002/asna.202113886

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, Gargee Chakraborty
Published: 21 January 2021
by Wiley
Astronomische Nachrichten, Volume 342, pp 103-109; doi:10.1002/asna.202113888

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Published: 21 January 2021
by Wiley
Astronomische Nachrichten, Volume 342, pp 96-102; doi:10.1002/asna.202113887

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, Andre R. C. Prado, Marco A. Souza, Nadja S. Magalhaes, , Andre R. C. Prado, Marco A. Souza, Nadja S. Magalhaes
Published: 21 January 2021
by Wiley
Astronomische Nachrichten, Volume 342, pp 115-122; doi:10.1002/asna.202113890

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Published: 21 January 2021
by Wiley
Astronomische Nachrichten, Volume 342, pp 128-134; doi:10.1002/asna.202113892

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Published: 20 January 2021
by Wiley
Astronomische Nachrichten, Volume 342, pp 75-80; doi:10.1002/asna.202113884

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Published: 20 January 2021
by Wiley
Astronomische Nachrichten, Volume 342, pp 485-496; doi:10.1002/asna.202113801

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, Ralph Neuhäuser, Markus Mugrauer, Richard Bischoff
Published: 19 January 2021
by Wiley
Astronomische Nachrichten, Volume 342, pp 553-577; doi:10.1002/asna.202113860

Abstract:
Runaway stars can result from core‐collapse supernovae in multiple stellar systems. If the supernova disrupts the system, the companion is ejected with its former orbital velocity. A clear identification of a runaway star can yield the time and place of the explosion, as well as orbital parameters of the pre‐supernova binary system. Previous searches have mostly considered O‐ and B‐type stars as runaway stars because they are always young in absolute terms (not much older than the lifetime of the progenitor) and can be detected up to larger distances. Here, we present a search for runaway stars of all spectral types. For late‐type stars, a young age can be inferred from the lithium test. We used Gaia data to identify and characterize runaway star candidates in nearby supernova remnants, obtained spectra of 39 stars with UVES at the VLT and HDS at the Subaru telescope, and found a significant amount of lithium in the spectra of six dwarf stars. We present the spectral analysis, including measurements of radial velocities, atmospheric parameters, and lithium abundances. Then, we estimate the ages of our targets from the Hertzsprung‐Russell diagram and, using the lithium test, present a selection of promising runaway star candidates and draw constraints on the number of ejected runaway stars compared to model expectations.
, Hao Shan, Hui Wang
Published: 1 January 2021
by Wiley
Astronomische Nachrichten, Volume 342, pp 369-376; doi:10.1002/asna.202113936

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