International Journal of Astronomy and Astrophysics

Journal Information
ISSN / EISSN : 21614717 / 21614725
Current Publisher: Scientific Research Publishing, Inc. (10.4236)
Total articles ≅ 357
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Latest articles in this journal

Lorenzo Zaninetti
International Journal of Astronomy and Astrophysics, Volume 10, pp 71-88; doi:10.4236/ijaa.2020.102006

Abstract:
The thin layer approximation applied to the expansion of a supernova remnant assumes that all the swept mass resides in a thin shell. The law of motion in the thin layer approximation is therefore found using the conservation of momentum. Here we instead introduce the conservation of energy in the framework of the thin layer approximation. The first case to be analysed is that of an interstellar medium with constant density and the second case is that of 7 profiles of decreasing density with respect to the centre of the explosion. The analytical and numerical results are applied to 4 supernova remnants: Tycho, Cas A, Cygnus loop, and SN 1006. The back reaction due to the radiative losses for the law of motion is evaluated in the case of constant density of the interstellar medium.
Lorenzo Zaninetti
International Journal of Astronomy and Astrophysics, Volume 10, pp 11-27; doi:10.4236/ijaa.2020.101002

Abstract:
The shape of the local bubble is modeled in the framework of the thin layer approximation. The asymmetric shape of the local bubble is simulated by introducing axial profiles for the density of the interstellar medium, such as exponential, Gaussian, inverse square dependence and Navarro-Frenk-White. The availability of some observed asymmetric profiles for the local bubble allows us to match theory and observations via the observational percentage of reliability. The model is compatible with the presence of radioisotopes on Earth.
Ibrahim Mohamed Selim, Passent Elkafrawy, Walid Dabour, Mohamed Eassa
International Journal of Astronomy and Astrophysics, Volume 10, pp 1-10; doi:10.4236/ijaa.2020.101001

Abstract:
The Virgo cluster of galaxies is of great importance to study the development of the universe due to its close distance from the earth as well as being the center of the local super cluster. The problem that faces Virgo cluster studies is that it shares the same right ascension (RA) and Declination (DEC) ranges with large number of background as well as foreground galaxies. This study aims to geometrically and statistically estimate Virgo cluster membership. The study employs Virgo cluster data, prepared by Harvard University. The radial velocity (RV) data of the Virgo cluster were treated and employed in exchange of missing galaxies’ third dimension, taking advantage of their proportionality. The data were treated by K-means algorithm, using Matlab 2014, and visual and logical exclusion of extremity galaxies to determine the rational center of the Virgo galaxies cluster. Results were presented, compared and discussed. Finally distances of galaxies from the Virgo cluster center were employed along with normal probability distribution characteristics to identify the most probable Virgo cluster members from the range of Virgo cluster of galaxies. The results showed that out of 17,466 objects surveyed in Virgo galaxy range, only few of galaxies were estimated to be genuine Virgo members.
Zaninetti Lorenzo, Lorenzo Zaninetti
International Journal of Astronomy and Astrophysics, Volume 10, pp 191-202; doi:10.4236/ijaa.2020.103010

Abstract:
The Maxwell-Boltzmann (MB) distribution for velocities in ideal gases is usually defined between zero and infinity. A double truncated MB distribution is here introduced and the probability density function, the distribution function, the average value, the rth moment about the origin, the root-mean-square speed and the variance are evaluated. Two applications are presented: 1) a numerical relationship between root-mean-square speed and temperature, and 2) a modification of the formula for the Jeans escape flux of molecules from an atmosphere.
Hoeneisen Bruce, Bruce Hoeneisen
International Journal of Astronomy and Astrophysics, Volume 10, pp 57-70; doi:10.4236/ijaa.2020.102005

Abstract:
We compare the observed galaxy stellar mass distributions in the redshift range with expectations of the cold ΛCDM and warm ΛWDM dark matter models, and obtain the warm dark matter cut-off wavenumber: . This result is in agreement with the independent measurements with spiral galaxy rotation curves, confirms that kfs is due to warm dark matter free-streaming, and is consistent with the scenario of dark matter with no freeze-in and no freeze-out. Detailed properties of warm dark matter can be derived from kfs. The data disfavors the ΛCDM model.
Nils-Axel Mörner, Jan-Erik Solheim, Ole Humlum, Stig Falk-Petersen
International Journal of Astronomy and Astrophysics, Volume 10, pp 97-164; doi:10.4236/ijaa.2020.102008

Abstract:
This is the first report of the Barents Sea Ice Edge (BIE) project. The BIE position has varied between latitude 76°N and above 82°N during the last 440 years. During the period 10,000 to 6000 years ago, Arctic climate was significantly warmer than today. We review various oceanic and atmospheric factors that may have an effect on the BIE position. The Gulf Stream beat with respect to alternations in flow intensity and N-S distribution plays a central role for the changes in climate and BIE position during the last millennium. This occurred in combination with external forcing from total solar irradiation, Earth’s shielding strength, Earth’s geomagnetic field intensity, Earth’s rotation, jet stream changes; all factors of which are ultimately driven by the planetary beat on the Sun, the Earth and the Earth-Moon system. During the last 20 years, we see signs of changes and shifts that may signal the end of the late 20th century warm period. The BIE position is likely to start advancing southward in next decade.
Haruka Tabata, Yoichi Itoh
International Journal of Astronomy and Astrophysics, Volume 10, pp 89-96; doi:10.4236/ijaa.2020.102007

Abstract:
The results of near-infrared photometric observations of a transit event of an extrasolar planet HAT-P-54b are presented herein. Precise near-infrared photometry was carried out using the Nayuta 2 m telescope at Nishi-Harima Astronomical Observatory, Japan and Nishi-Harima Infrared Camera (NIC). 170 J-, H-, and Ks-band images were taken in each band in 196 minutes. The flux of the planetary system was observed to decrease during the transit event. While the Ks-band transit depth is similar to that in the r-band, the J- and H-band transits are deeper than those in the Ks-band. We constructed simple models of the planetary atmosphere and found that the observed transit depths are well reproduced by inflated atmosphere containing H2S molecule.
Bruce Hoeneisen
International Journal of Astronomy and Astrophysics, Volume 10, pp 203-223; doi:10.4236/ijaa.2020.103011

Abstract:
We measure properties of dark matter in four well motivated scenarios: fermions with ultra-relativistic thermal equilibrium (URTE), bosons with URTE, fermions with non-relativistic thermal equilibrium (NRTE), and bosons with NRTE. We attempt to discriminate between these four scenarios with studies of spiral galaxy rotation curves, and galaxy stellar mass distributions. The measurements show evidence for boson dark matter with a significance of 3.5σ, and obtain no significant discrimination between URTE and NRTE.
Lorenzo Zaninetti
International Journal of Astronomy and Astrophysics, Volume 10, pp 165-189; doi:10.4236/ijaa.2020.102009

Abstract:
Here we extend the conservation of energy in the framework of the thin layer approximation to the asymmetrical case. Four types of interstellar mediums are analysed, in which the density follows an inverse square profile, a power law profile, an exponential profile and a toroidal profile. An analytical solution for the radius as a function of time and the polar angle in spherical coordinates is derived in the case of the inverse square profile. The analytical and numerical results are applied to two supernova remnants: SN 1987A and SN 1006. The back reaction due to the radiative losses is evaluated in the case of the inverse square profile for the surrounding medium. Two models for the image formation are presented, which explain the triple ring visible in SN 1987A and the jet feature of SN 1006.
Lenser Aghalovyan​
International Journal of Astronomy and Astrophysics, Volume 10, pp 224-234; doi:10.4236/ijaa.2020.103012

Abstract:
The central interaction of bodies is investigated, which enhances the Newtonian interaction by the exponential factor. As a consequence, it has been shown that Black Holes are subordinate to this enhanced interaction. All Black Holes can be systematized in accordance with their mass, the radius of the event horizon and the gravitational field intensity exponent, created by the Black Hole.
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