Clustering of galaxies on scales of ≤10<Emphasis Type="Italic">h</Emphasis><Superscript>−1</Superscript> based on the coma,bridge, and A1367 clusters

A correlation analysis is made of the spatial distribution of galaxies in the Coma, Bridge, and A1367 clusters, which form the Coma supercluster. The scale of the clustering of galaxies and the variation in their density distribution with the main parameters of the galaxies– luminosity, morphological type, and observed H I deficiency in the 21 cm line– are evaluated. The mass-to-luminosity ratios are computed for the spiral galaxies in the Coma, Bridge, and A1367 clusters. It is suggested that a larger fraction of hypothetical dark matter may be concentrated in the spiral galaxies which predominantly populate the subclusters previously identified by us within these clusters than in the spiral galaxies observed in the peripheral regions of the clusters.     

A preliminary radial-velocity curve for the star <Emphasis Type="Italic">θ</Emphasis><Superscript>1</Superscript> Ori D

We measured the radial velocity of the star θ¹ Ori D from IUE spectra and used published observations. Based on these data, we determined the period of its radial-velocity variations, P=20.2675±0.0010 days, constructed the phase radial-velocity curve, and solved it by least squares. The spectroscopic orbital elements were found to be the following: the epoch of periastron passage E_p=JD 2430826.6±0.1, the system's center-of-mass velocity /Gg=32.4±1.0 km s^?1, K=14.3±1.5 km s^?1, Ω=3.3±0.1 rad, e=0.68±0.09, a₁ sin i = 3 × 10¹⁰ km, and f₁ = 0.0025M_⊙. Twice the period, P=40.528±0.002 days, is also consistent with the observations.     

Composition of Cosmic Rays with <Emphasis Type="Italic">E</Emphasis><Superscript>0</Superscript> ⩾ 10<Superscript>17</Superscript> eV Based on Data from the Ground Scintillation Detectors of the Yakutsk EAS Array

The lateral distribution of cascade particles in extensive air showers from cosmic rays with energy E⁰ ? 10¹⁷ eV has been studied at the Yakutsk array by the ground scintillation detectors over the period of continuous observations 1977–2017. The experimental data are compared with those computed with various models for the development of extensive air showers from the CORSIKA software package. The best agreement between the theory and experiment is observed for the QGSjet-01-d model. In the energy range (1?20)× 10¹⁷ eV there is a change in the cosmic-raymass composition from 〈lnA〉 ≈ 2.5 to the proton one.     

Study of the anisotropy of cosmic rays with <Emphasis Type="Italic">E</Emphasis><Subscript>0</Subscript>≥5×10<Superscript>16</Superscript> eV using Yakutsk EAS array data

We present the results of a harmonic analysis of and search for clusters in the arrival directions of cosmic rays with energies E₀≥5×10¹⁶ eV and zenith angles ?≤53° detected at the Yakutsk extensive air shower (EAS) array from 1974 to 2002. We show that the phase of the first harmonic periodically varies greatly and takes on nonrandom values at a confidence level ≥4σ. These phases point to the Supergalactic plane (the Local supercluster of galaxies).     

Quintessence cosmology with a traversable wormhole,massive decaying gravitons and with varying <Emphasis Type="Italic">G</Emphasis> and <Emphasis Type="Italic">Λ</Emphasis>

In this work, we explore many cosmological implications of a four-dimensional cosmology dominated by quintessence with a static traversable wormhole, spatio-temporal varying G and by taking into account a decaying cosmological constant and a decaying graviton mass by means of an additional bimetric tensor in Einstein’s field equations proposed by Visser in 1998.     

Radial pulsations of helium stars with masses from 1 to 10 <Emphasis Type="Italic">M</Emphasis><Subscript>⊙</Subscript>

We present the results of our hydrodynamic calculations of radial pulsations in helium stars with masses 1 M_⊙ ≤ M ≤ 10 M_⊙, luminosity-to-mass ratios 1 × 10³L_⊙/M_⊙ ≤ L/M ≤ 2 × 10⁴L_⊙/M_⊙, and effective temperatures 2 × 10⁴ K ≤ T_eff ≤ 10⁵ K for mass fractions of helium Y=0.98 and heavy elements Z=0.02. We show that the lower boundary of the pulsation-instability region corresponds to L/M ～ 10³L_⊙/M_⊙ and that the instability region for L/M ? 5 × 10³L_⊙/M_⊙ is bounded by effective temperatures T_eff ? 3 × 10⁴ K. As the luminosity rises, the instability boundary moves into the left part of the Hertzsprung-Russell diagram and radial pulsations can arise in stars with effective temperatures T_eff ? 10⁵ K at L/M ? 7 × 10³L_⊙/M_⊙. The velocity amplitude for the outer boundary of the hydrodynamic model increases with L/M and lies within the range 200 ? ΔU ? 700 km s^?1 for the models under consideration. The periodic shock waves that accompany radial pulsations cause a significant change of the gas-density distribution in the stellar atmosphere, which is described by a dynamic scale height comparable to the stellar radius. The dynamic instability boundary that corresponds to the separation of the outer stellar atmospheric layers at a superparabolic velocity is roughly determined by a luminosity-to-mass ratio L/M ～ 3 × 10⁴L_⊙/M_⊙.     

Precipitable water vapor (PWV) estimations from the site of the Eastern Anatolia Observatory<Superscript>∗</Superscript> (DAG), a new astronomical observatory in Turkey

We present preliminary statistics on the precipitable water vapor (PWV) content over the Karakaya Hills in Erzurum city, where the largest optical and near-infrared astronomical telescope in Turkey will be operated. Since the observatory will observe in the near-infrared (NIR), it is intended to perform PWV measurements of the atmosphere above the site by using signal delays in Global Positioning System (GPS) communication. The analysis of the GPS data recorded on the summit for almost one year shows that the atmosphere over the site of the observatory, which has an altitude of 3170 m, has favorable conditions for NIR observations. From GPS measurements, we report that the site had an average PWV of 3.2 mm and a median PWV of 2.7 mm between October 6, 2016, and June 15, 2017. We also present the time dependency of the PWV content and the correlations between the amount of PWV and the other meteorological records gathered from radiosonde flights and ground-based measurements.     

Second species solutions with an 0(μ v ), 0<v<1, near-Moon passage

This paper illustrates the application of the theory for second species solutions with an 0( ^v ), 0<v<1, near-Moon passage to first species-second species bifurcations and to second species-second species bifurcations. It also corrects and improves the asymptotic approximations obtained in the author's previous work on this subject and it establishes a local form of Broucke's Principle for the types of bifurcations studied in this paper.This work was supported by the National Science Foundation under Grant MCS 7703591.     

CCD <Emphasis Type="Italic">UBV</Emphasis> photometric study of five open clusters—Dolidze 36, NGC 6728, NGC 6800, NGC 7209, and Platais 1

In this study, we present CCD UBV photometry of poorly studied open star clusters, Dolidze 36, NGC 6728, NGC 6800, NGC 7209, and Platais 1, located in the first and second Galactic quadrants. Observations were obtained with T100, the 1-m telescope of the TÜB?TAK National Observatory. Using photometric data, we determined several astrophysical parameters such as reddening, distance, metallicity and ages and from them, initial mass functions, integrated magnitudes and colours. We took into account the proper motions of the observed stars to calculate the membership probabilities. The colour excesses and metallicities were determined independently using two-colour diagrams. After obtaining the colour excesses of the clusters Dolidze 36, NGC 6728, NGC 6800, NGC 7209, and Platais 1 as \(0.19\pm0.06\), \(0.15\pm0.05\), \(0.32\pm0.05\), \(0.12\pm 0.04\), and \(0.43\pm0.06\) mag, respectively, the metallicities are found to be \(0.00\pm0.09\), \(0.02\pm0.11\), \(0.03\pm0.07\), \(0.01\pm0.08\), and \(0.01\pm0.08\) dex, respectively. Furthermore, using these parameters, distance moduli and age of the clusters were also calculated from colour-magnitude diagrams simultaneously using PARSEC theoretical models. The distances to the clusters Dolidze 36, NGC 6728, NGC 6800, NGC 7209, and Platais 1 are \(1050\pm90\), \(1610\pm190\), \(1210\pm150\), \(1060\pm90\), and \(1710\pm250\) pc, respectively, while corresponding ages are \(400\pm100\), \(750\pm150\), \(400\pm100\), \(600\pm100\), and \(175\pm50\) Myr, respectively. Our results are compatible with those found in previous studies. The mass function of each cluster is derived. The slopes of the mass functions of the open clusters range from 1.31 to 1.58, which are in agreement with Salpeter’s initial mass function. We also found integrated absolute magnitudes varying from ?4.08 to ?3.40 for the clusters.