Spectroscopic Redshift Determination for a Sample of Distant Quasars Detected by the SRG Observatory Based on RTT-150 Observations. II

Astronomy Letters - Results of the spectroscopic observations at the 1.5-m Russian–Turkish telescope for another group of 12 X-ray sources discovered by the eROSITA telescope onboard the SRG...     

Spectroscopic Redshift Measurements for Galaxy Clusters from the Lockman Hole Survey with the eROSITA Telescope Onboard the SRG Observatory

Astronomy Letters - We present the first results of our program of optical observations for galaxy clusters from the Lockman Hole X-ray survey with the eROSITA telescope onboard the SRG space...     

Observations of Candidates for Eclipsing Cataclysmic Variables with the RTT-150 Telescope

Astronomy Letters - We present the results of our photometric and spectroscopic observations. We have studied four cataclysmic variable stars: 2XMM J183251.4-100106, MLS1809017 J224712+461815,...     

Spectroscopic Redshift Measurements for Galaxy Clusters from the Planck Survey and Observations of These Clusters in the SRG/eROSITA Survey

Astronomy Letters - We present the results of our spectroscopic redshift measurements for galaxy clusters detected previously from Planck all-sky survey data as well as Sloan Digital Sky Survey and...     

Optical Spectroscopy of Quasars Discovered by SRG/eROSITA with a 2.5-m Telescope at the Caucasus Mountain Observatory of SAI MSU

Astronomy Letters - Based on observations with the transient double-beam spectrograph (TDS) at the 2.5-m telescope of the Caucasus Mountain Observatory of SAI MSU, we have determined the redshifts...     

Optical Identification of Candidates for Active Galactic Nuclei Detected by the Mikhail Pavlinsky ART-XC Telescope Onboard the SRG Observatory during an All-Sky X-ray Survey

Astronomy Letters - We present the results of our identification of eight objects from the preliminary catalogue of X-ray sources detected in the 4–12 keV energy band by the Mikhail Pavlinsky...     

Spectroscopic study of the optical counterpart to the fast X-ray transient IGR J17544-2619 based on observations at the 1.5-m RTT-150 telescope

We present the results of our long-term photometric and spectroscopic observations at the Russian–Turkish RTT-150 telescope for the optical counterpart to one of the best-known sources, representatives of the class of fast X-ray transients, IGR J17544-2619. Based on our optical data, we have determined for the first time the orbital and physical parameters of the binary system by the methods of Doppler spectroscopy.We have calculated theoretical spectra of the optical counterpart by applying non- LTE corrections for selected lines and obtained the parameters of the stellar atmosphere (T _eff = 33 000 K, log g = 3.85, R = 9.5 R _⊙, and M = 23 M _⊙). The latter suggest that the optical star is not a supergiant as has been thought previously.     

Analysis of optical light curves for the components of the gravitationally lensed quasar SBS 1520+530 based on observations with the 1.5-m RTT-150 telescope in 2001–2005

We present the R _c-band light curves for components A and B of the gravitationally lensed quasar SBS 1520+530 obtained during 2001–2005 with the 1.5-m Russian-Turkish Telescope (RTT-150) at the TUBITAK National Observatory (Turkey). Based on an analysis of the data for the period 2001–2002, we have estimated the time delay of the brightness fluctuations between components A and B of the quasar to be 128 days. This time delay agrees with its previously published values for the periods 1999–2001 and 2003–2004. Using all of the published data on the brightnesses of components A and B of SBS 1520+530 for the 6-year period, we have found at least two microlensing events. One event has the pattern of a long-term linear trend; the duration of the other event is several hundred days.     

Refinement of the Gnevyshev-Waldmeier Rule Based on a 140-Year Series of Observations

Astronomy Letters - The Gnevyshev—Waldmeier rule relating the lifetimes of sunspot groups and their areas has been verified on an interval of ≈140 years, which exceeds the one used by...     

Spectroscopic Determination of C,N,and O Abundances of Solar-analog Stars Based on the Lines of Hydride Molecules

Photospheric C,N,and O abundances of 118 solar-analog stars were determined by applying the synthetic-fitting analysis to their spectra in the blue or near-UV region comprising lines of CH,NH,and OH molecules,with an aim of clarifying the behaviors of these abundances in comparison with[Fe/H].It turned out that,in the range of-0.6■[Fe/H]■+0.3,[C/Fe]shows a marginally increasing tendency with decreasing[Fe/H]with a slight upturn around[Fe/H]～0,[N/Fe]tends to somewhat decrease toward lower[Fe/H],a...     

The 26 December 2001 Solar Event Responsible for GLE63. I. Observations of a Major Long-Duration Flare with the Siberian Solar Radio Telescope

Ground level enhancements (GLEs) of cosmic-ray intensity occur, on average, once a year. Because they are rare, studying the solar sources of GLEs is especially important to approach understanding their origin. The SOL2001-12-26 eruptive-flare event responsible for GLE63 seems to be challenging in some aspects. Deficient observations limited our understanding of it. Analysis of additional observations found for this event provided new results that shed light on the flare configuration and evolution. This article addresses the observations of this flare with the Siberian Solar Radio Telescope (SSRT). Taking advantage of its instrumental characteristics, we analyze the detailed SSRT observations of a major long-duration flare at 5.7 GHz without cleaning the images. The analysis confirms that the source of GLE63 was associated with an event in active region 9742 that comprised two flares. The first flare (04:30?–?05:03 UT) reached a GOES importance of about M1.6. Two microwave sources were observed, whose brightness temperatures at 5.7 GHz exceeded 10 MK. The main flare, up to an importance of M7.1, started at 05:04 UT and occurred in strong magnetic fields. The observed microwave sources reached a brightness temperature of about 250 MK. They were not static. After appearing on the weaker-field periphery of the active region, the microwave sources moved toward each other nearly along the magnetic neutral line, approaching the stronger-field core of the active region, and then moved away from the neutral line like expanding ribbons. These motions rule out an association of the non-thermal microwave sources with a single flaring loop.     

CMEs in the Heliosphere: I. A Statistical Analysis of the Observational Properties of CMEs Detected in the Heliosphere from 2007 to 2017 by STEREO/HI-1

We present a statistical analysis of coronal mass ejections (CMEs) imaged by the Heliospheric Imager (HI) instruments on board NASA’s twin-spacecraft STEREO mission between April 2007 and August 2017 for STEREO-A and between April 2007 and September 2014 for STEREO-B. The analysis exploits a catalogue that was generated within the FP7 HELCATS project. Here, we focus on the observational characteristics of CMEs imaged in the heliosphere by the inner (HI-1) cameras, while following papers will present analyses of CME propagation through the entire HI fields of view. More specifically, in this paper we present distributions of the basic observational parameters – namely occurrence frequency, central position angle (PA) and PA span – derived from nearly 2000 detections of CMEs in the heliosphere by HI-1 on STEREO-A or STEREO-B from the minimum between Solar Cycles 23 and 24 to the maximum of Cycle 24; STEREO-A analysis includes a further 158 CME detections from the descending phase of Cycle 24, by which time communication with STEREO-B had been lost. We compare heliospheric CME characteristics with properties of CMEs observed at coronal altitudes, and with sunspot number. As expected, heliospheric CME rates correlate with sunspot number, and are not inconsistent with coronal rates once instrumental factors/differences in cataloguing philosophy are considered. As well as being more abundant, heliospheric CMEs, like their coronal counterparts, tend to be wider during solar maximum. Our results confirm previous coronagraph analyses suggesting that CME launch sites do not simply migrate to higher latitudes with increasing solar activity. At solar minimum, CMEs tend to be launched from equatorial latitudes, while at maximum, CMEs appear to be launched over a much wider latitude range; this has implications for understanding the CME/solar source association. Our analysis provides some supporting evidence for the systematic dragging of CMEs to lower latitude as they propagate outwards.     

Investigation of galaxies in the second byurakan sky survey. I. Spectroscopic observations in a field at 15h30m, +59°

The results of spectroscopic observations of 30 galaxies from the Second Byurakan Spectral Sky Survey in a field of 16 square degrees centered at coordinates a = 15^h30^m, δ = + 53°are presented. The spectra were obtained on the 6-m telescope of the Special Astrophysical Observatory, Russian Academy of Sciences, in the wavelength range of 4000–7400 Å with 15 Å resolution. Emission lines are present in the spectra of most of the galaxies. Redshifts and absolute stellar magnitudes were determined for all the galaxies.     

1998年9月23 日复杂太阳爆发射电联合观测的初步分析

利用北京天文台1998.09.23日1-2GHz和2.6-3.8GHz频谱仪观测到的一个Ⅲ-Ⅳ型复杂大爆发，结合俄罗斯SSRT和德国分米-米波动态频谱仪的观测资料，进行了初步的比对分析，拓展了关于日冕电子加速和日冕磁结构方面的一些研究内容，简单地注释了一些可研究的现象和运动Ⅳ型爆发及多重脉动的辐射机制。     

Moment of inertia of a neutron star. I. Relativistic equation for the accumulated moment of inertia

A relativistic, first-order differential equation is derived for the accumulated moment of inertia of a spherically symmetric celestial body. An approximate equation is proposed to describe the contribution of relativistic effects to the moment of inertia of a superdense star. For configurations of an incompressible fluid, this approximation describes the results of the numerical calculations of Chandrasekhar and Miller to within 5% in the entire range of central pressures from 0 to ∞. Translated from Astrofizika, Vol. 40, No. 1, pp. 87–96, January–March, 1997.     

Method for analyzing the spatial distribution of galaxies on gigaparsec scales. I. initial principles

The initial principles of a method for analyzing the spatial distribution of visible matter in the universe with structures on size scales of thousands of Mpc are discussed. This method is based on analyzing the distribution N(z) of the photometric redshifts of galaxies in deep fields using large bins Δ z=0.1–0.3. Fluctuations in the numbers of galaxies in these bins in terms of redshifts are caused by Poisson noise, correlated structures, and systematic errors in estimating photo-z. This method involves covering a sufficiently large region of the celestial sphere with a grid of deep multi-band surveys with a cell size on the order of 10º×10º, with deep fields of size ～10'×10' observed with 3-10 meter telescopes at its nodes. The distribution of the photometric redshifts of the galaxies within each deep field will yield information on the radial extent of superlarge structures, while comparing the radial distributions in neighboring fields will yield information on the tangential extent of these structures. A necessary element of this method is an analysis of possible distortions in the radial distributions of the galaxies associated with the technique for evaluating the photometric redshifts.