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Vol 45, No 2 (2019)
- Year: 2019
- Articles: 6
- URL: https://journal-vniispk.ru/1063-7737/issue/view/11988
Article
Optical Identifications of Galaxy Clusters Among Objects from the Second Planck Catalogue of Sunyaev–Zeldovich Sources
Abstract
We present the results of optical identifications and spectroscopic redshift measurements for galaxy clusters from the second Planck catalogue of Sunyaev-Zeldovich sources. We used the data of observations with the 1.5-m Russian-Turkish telescope (RTT150), the 1.6-m Sayan Observatory AZT-33IK telescope, the 3.5-m Calar Alto telescope, and the 6-m SAO RAS telescope (Bolshoi Teleskop Azimutalnyi, BTA). For the observations we selected Sunyaev-Zeldovich sources unidentified with galaxy clusters with known redshifts. The observations have been carried out for three years, as a result of which we obtained direct images in various filters for a set of galaxy clusters and spectra for the brightest red-sequence galaxies of these clusters. For 38 galaxy clusters we obtained spectroscopic redshift measurements.
49-61
Populations of Sources in a Galactic Plane Survey with the ART-XC Telescope of the Spectrum-RG Observatory: Simulations
Abstract
The possibility of conducting a Galactic plane survey at energies above 5 keV with the ART-XC telescope onboard the Spectrum-Röntgen-Gamma (SRG) observatory during the satellite’s flight to the Lagrange point L2 is considered. One of the possible fields for such a survey is proposed. We show that it will be possible to detect ∼100 cataclysmic variables with luminosities 1031−1034 erg s−1 in a survey with an area of 10 deg2 and a duration of 10 days. Such a representative sample may allow the luminosity function and other properties of the population of cataclysmic variables in the Galaxy to be refined.
62-70
Wind of Presupernova IIn SN 1997eg
Abstract
Spectra and phototometry of type IIn supernova SN 1997eg are used to determine properties of the circumstellar gas lost by the presupernova during the latest 200 years before the explosion. The analysis of narrow Hα and [Fe X] 6374 Å results in the wind velocity u = 20 km s−1, significantly lower than the earlier accepted value (160 km s−1) upon the bases of the radial velocity of a blue absorption wing of the narrow Hα. That high velocity of the wind in our picture is related to the preshock gas accelerated by the cosmic ray precursor. The modelling of the circumstellar interaction results in the wind density parameter Ṁ/u that being combined with the wind velocity suggests the presupernova mass loss rate of 1.6 × 10−3M⊙ yr−1. The wind density is consistent with the [Fe X] 6374 Å luminosity. The model Hα luminosity also agrees with the observational value. Recovered wind properties indicate that the presupernova at the final evolutionary stage was a massive red supergiant with a high mass loss rate, but not the LBV-supergiant as suggested earlier.
71-80
Simulation of a Hydrodynamic Stellar Wind from a Rapidly Rotating Star
Abstract
The mechanism for the formation of disk-like flows from rapidly rotating Be stars is not yet clear. An axisymmetric hydrodynamic stellar wind flow from a rapidly rotating star has been simulated numerically as a step in solving this problem. The change in the shape of the star as it rotates and the turbulence excited in the stellar wind at Reynolds numbers ∼109−1013 are taken into account. Calculations show the formation of a disk-like flow from the stellar surface at the equator, which expands into the polar regions due to a pressure gradient on scales of the order of the stellar radius. A poloidal velocity vortex is formed at high latitudes. No turbulence is excited near the equator within the simplest standard models and, therefore, no quasi-Keplerian disk-like flow emerges in the equatorial plane. A dependence of the total mass flux on the stellar rotation rate at various surface temperatures has been obtained.
81-91
Search for Evolutionary Changes in the Periods of Cepheids: CF Cas
Abstract
For the classical Cepheid CF Cas we have constructed an O-C diagram spanning a time interval of 129 years. The O-C diagram has the shape of a parabola, which has made it possible to determine for the first time the quadratic light elements and to calculate the rate of evolutionary decrease in the period, dP/dt = −0.050 (±0.006) syr−1, in agreement with the results of theoretical calculations for the second crossing of the instability strip. The available data reduced by the Eddington-Plakidis method show no random period fluctuations, i.e., the parabola on the O-C diagram reflects a real evolutionary decrease in the period.
92-103
Physical Parameters of the Asteroid 2017 VR12 from Radar and Photometric Observations
Abstract
Results of radar and photometric observations of the asteroid 2017 VR12 are presented. The observations were carried out during the asteroid’s close approach to the Earth in 2018 on March 5 with 32-m radio telescopes at the Zelenchukskaya and Badary Observatories and on March 6 with a 0.65-m optical telescope at the Ussuriysk Astrophysical Observatory. The asteroid’s radar observations were performed in the bistatic mode at a frequency of 8.56 GHz in combination with the 70-m Goldstone antenna. The echo power spectra for the asteroid were obtained as a result of the observations. The poleon silhouette breadth of this asteroid is 138 ± 14 m. We have estimated the radar albedos, 0.32 ± 0.04 and 0.31 ± 0.04, and the circular polarization ratios, 0.36 ± 0.02 and 0.34 ± 0.01, for the Zelenchukskaya and Badary Observatories, respectively. Based on our photometric observations, we have obtained the asteroid’s light curve, determined its rotation period, 1.378 ± 0.03 h, and constructed a two-dimensional surface contour.
104-107