Observations of the binary star 61 Cyg on the 26 inch refractor at the Pulkovo observatory

Results from an analysis of a forty year series of photographic observations of the binary star 61 Cyg on the 26 inch refractor at the Pulkovo Observatory are presented. The orbit is constructed and the sum of the masses of the components is determined from the relative positions of the components. A study of the individual motions of the components of 61 Cyg relative to the surrounding stars yields their mass ratio and the masses of the main and secondary components, 0.74 and 0.46 solar masses, respectively. The relative motion of the components is found to have a fluctuating component with a period of 6.5 years which may be caused, in particular, by the presence in the system of a dark, low-mass companion. __________ Translated from Astrofizika, Vol. 49, No. 3, pp. 453–465 (August 2006).     

Installation of solar chromospheric telescope at the Indian Astronomical Observatory,Merak

We report the observations of the solar chromosphere from a newly commissioned solar telescope at the incursion site near Pangong Tso lake in Merak (Leh/Ladakh). This new \(\hbox {H}_{\alpha }\) telescope at the Merak site is identical to the Kodaikanal \(\hbox {H}_{\alpha }\) telescope. The telescope was installed in the month of August 2017 at the Merak site. The telescope consists of a 20-cm doublet lens with additional re-imaging optics. A Lyot filter with 0.5 Å passband isolates the Balmer line of the hydrogen spectra to make the observations of the solar chromosphere. The observations made in \(\hbox {H}_{\alpha }\) wavelength delineates the magnetic field directions at the sunspot and the quiet regions. A CCD detector records the images of the chromosphere with a pixel resolution of 0.27\(^{\prime \prime }\) and covers 9.2\(^{\prime }\) field-of-view. This telescope has a good guiding system that keeps the FoV in the intended position. We report the development of control software for tuning the filter unit, control detector system, observations and calibration of the data to make it useful for the scientific community. Some preliminary results obtained from the Merak \(\hbox {H}_{\alpha }\) telescope are also presented. This high altitude facility is a timely addition to regularly obtain \(\hbox {H}_{\alpha }\) images around the globe.     

Solar research at the Pulkovo Astronomical Observatory

The paper deals with the review of works on solar observations at Abastumani Astrophysical Observatory during the past 12 years. The works accomplished on the basis of patrol observations, with the horizontal solar telescope, small and large coronagraphs, and those based on the data obtained during eclipse observations are discussed separately.     

Kottamia 74-inch telescope discovery of the new eclipsing binary KAO-EGYPT J225702.44+523222.1.: First CCD photometry and light curve analysis

We present the first multicolor CCD photometry for the newly discovered binary system KAO-EGYPT J225702.44+523222.1. New times of light minimum and new ephemeris were obtained. The VR I light curves were analyzed using WD code, the difference in maximum light at phase 0.25 is modeled with a cool spot on the secondary component. The solution show that the system is A-subtype, overcontact binary with fill-out factor = 42% and low mass ratio, q = 0.275. The two components of spectral types K0 and K1 and the primary component is the massive one. The position of both components on the M-L and M–R relations revealed that the primary component is a main sequence star while the secondary is an evolved component.     

Spectral study of BIG objects on the 2.6-m telescope at the Byurakan astrophysical observatory

Results of spectral observations of 45 objects from the BIG sample (corresponding to 35 IRAS sources) obtained on the 2.6-m telescope at the BAO are reported. Emission lines are observed for 42 galaxies, 1 object is an absorption galaxy, and 2 turned out to be stars. The red shifts are determined, the radial velocities, distances, sizes, and absolute stellar magnitudes are calculated, the parameters of the spectral lines are determined, the objects are classified according to their activity type, and the IR and far IR luminosities are calculated. Of the 42 emission galaxies, 1 was type Sy2, 2 were LINERs, 1 was an AGN (Sy2 or LINER), 4 were composite, 25 were HII (including 6 with nuclear star-formation activity), and 9 were Em of undetermined type (3 of which may be AGN). Calculations show that 23 of the objects are LIG. A physical coupling is discovered for 9 multiple systems. Spectra of some of the galaxies are shown. __________ Translated from Astrofizika, Vol. 49, No. 1, pp. 23–40 (February 2006).     

A hard X-ray sky survey with the SIGMA telescope of the GRANAT observatory

The SIGMA X-ray telescope accumulated the images of more than a quarter of the sky during the in-orbit operation of the GRANAT observatory. The longest exposure time (～9 million s) was spent on the observations of the Galactic center region. We give an overview of the SIGMA X-ray observations and report the sensitivities achieved in various regions of the sky.     

Optical characteristics of the whipple observatory TeV gamma-ray imaging telescope

In TeV -ray astronomy, large mirrors are used to collect erenkov light from electromagnetic cascades in the atmosphere in order to obtain low energy thresholds. The flux sensitivity of TeV -ray detectors is limited by background due to erenkov light bursts from isotropic, cosmic-ray showers which are much more numerous than -ray showers. It has recently been established that most of this background can be eliminated on the basis of the shapes of erenkov light images on the focal plane of a telescope. In order for this technique to work, the light collector must have adequate resolution over a relatively wide field of view. In this paper, the optical characteristics of the 10 m reflector used in the imaging detection of the Crab Nebula are examined and contrasted with those of a standard parabolic design. This 10 m reflector has a unique (Davies-Cotton) design with small spherical facet mirrors placed on spherical support structure with radius equal to exactly 1/2 the curvature radius of the facet mirrors. The off-axis focusing properties of this type of telescope have not been examined previously.     

Positional observations of small solar system bodies with the SBG telescope at the Astronomical Observatory of the Ural Federal University

The telescope SBG (D = 0.42 m, F = 0.76 m) at the Kourovka Astronomical Observatory of the Ural Federal University has undergone an upgrade in 2005–2006. A CCD camera (Apogee Alta U32) and a new drive system were installed, and a new system for telescope and observation control was implemented. This upgrade required verifying the astrometric quality of the telescope. The data processing approaches tested when searching for the optimum CCD image processing technique combined TYCHO2 and UCAC2 catalogues with various reduction models and methods for choosing reference stars. Lorentzian and Moffat profiles were used in the measurement of pixel coordinates. It was demonstrated that the accuracy of SBG observations of main-belt asteroids with precisely determined orbits depends on their brightness and varies from 0.06” (11.5 ^m ) to 0.4” (18.5 ^m ). Regular SBG observations of comets and asteroids (mostly near-Earth and potentially hazardous ones) have been performed since 2007. Coordinates of 8515 positions of 720 asteroids and more than 1000 positions of 40 comets were obtained. The RMS deviations of observed coordinates from their calculated values are typically smaller than 1”: the average deviations for asteroids are 0.33” (in right ascension) and 0.34” (in declination); the corresponding values for comets are 0.37” (in α) and 0.38” (in δ). The results of observations are sent to the Minor Planet Center and are used to determine orbits more accurately and solve other fundamental and applied problems.     

Kottamia 74-inch telescope discovery of the new eclipsing binary 2MASS J20004638 + 0547475.: First CCD photometry and light curve analysis

A CCD photometric study is presented for the eclipsing binary system 2MASS J20004638 + 0547475. Observations of the system were obtained in the V, R and I colours with the 2Kx2K CCD attached to 1.88 m Kottamia Optical Telescope. New times of light minimum and new ephemeris were obtained. The V, R and I light curves were analyzed using the PHOEBE 0.31 program to determine geometrical and physical parameters of the system. The results show that 2MASS J20004638 + 0547475, is A-Type WUMa and is an overcontact binary with high fill-out factor = 69%. The current evolutionary status of the system indicates that the primary component lies very close to the main sequence while the secondary is evolved. The asymmetric maxima were studied and a modeling of the hot spot parameters is given.     

Studying Blazhko RR Lyrae stars with the 24‐inch telescope of the Konkoly Observatory

About a dozen field RR Lyrae stars have been observed with the 24‐inch Heyde‐Zeiss telescope of the Konkoly Observatory at Svábhegy, Budapest, since its refurbishment in 2003. Most of the observing time is allocated for the investigation of the Blazhko modulation, a phenomenon that still does not have a satisfactory explanation. The obtained multicolour CCD observations are unique in extent. The accuracy of the measurements makes it possible to detect low amplitude modulation of the light curve as well. The discovery of Blazhko stars with low modulation amplitudes warns that the incidence rate of the Blazhko modulation is, in fact, much larger than it was previously expected. This makes the efforts exploring the cause of the modulation even more important. A summary of our measurements and results achieved during the last 3 years is presented. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Spectroscopic research with the Hartebeesthoek radio telescope

Research into star-forming regions, evolved HII regions, late-type stars with circumstellar dust shells and comet Halley using spectroscopic observations made with the Hartebeesthoek radio telescope is reviewed.     

Light pollution and night sky brightness at the site of Kottamia Observatory

Photoelectric measurements of the night sky brightness and the light pollution of Kottamia Observatory have been carried out and the deduced results are expressed in mag/sec². The maximum brightness of the sky in the direction of Cairo city at zenith distance 45° and azimuth 70° when the sun is almost 60° below the horizon are 22.68; 21.54 and 19.82 mag/sec² for blue, yellow and red colours respectively. The corresponding values of night sky background are 22.94; 21.85 and 20.14 mag/sec² respectively.The isophotes of the sky brightness at Kottamia Observatory have been drawn for blue, yellow and red colours. The variations of the night sky brightness and the (B-V) colour index with altitude of the observed point have been studied.The light pollution and the night sky brightness at the site of Kottamia Observatory is compared with that deduced by different investigators at other sites. It has been shown that the sky brightness at zenith distance 45° at Kottamia Observatory site is similar to Kitt Peak and Palomar Observatory sites. Kottamia Observatory site is slightly brighter than Junipero Serra while it is darker than Mount Hamilton and San Jose sites. The comparative results have been carried out at blue and yellow colours. No comparison is obtained at red as there is no data published for the red colour.     

Normal galaxies in the all-sky survey by the eROSITA X-ray telescope of the Spectrum-X-Gamma observatory

We analyze the statistical properties of normal galaxies to be detected in the all-sky survey by the eROSITA X-ray telescope of the Spectrum-X-Gamma observatory. With the current configuration and parameters of the eROSITA telescope, the sensitivity of a 4-year-long all-sky survey will be ≈10^?14 erg s^?1 in the 0.5–2 keV band. This will allow ～(1.5–2) × 10⁴ normal galaxies with approximately the same contribution of star-forming and elliptical galaxies to be detected. All galaxies of the X-ray survey are expected to enter into the existing far-infrared (IRAS) or near-infrared (2MASS) catalogs; the sample of star-forming galaxies will be approximately equivalent in sensitivity to the sample of star-forming galaxies in the IRAS catalog of infrared sources. Thus, a large homogeneous sample of normal galaxies with measured X-ray, near-infrared, and far-infrared fluxes will be formed. About 90% of the galaxies in the survey are located within ～200–400 Mpc. A typical (most probable) galaxy will have a luminosity log L _X ～ 40.5–41.0, will be located at a distance of ～70–90 Mpc, and will be either a star-forming galaxy with a star formation rate of ～20M _⊙ yr^?1 whose X-ray emission is produced by ultraluminous X-ray sources (ULXs) or an elliptical galaxy with amass log M _* ～ 11.3 emitting through to a hot interstellar gas. The galaxies within 35 Mpc will collectively contain ～10² ULXs with luminosities log L _X > 40, ～80% of whichwill be the only luminous source in the galaxy. Thus, although the angular resolution of the eROSITA telescope is too low for the luminosity function of compact sources in galaxies to be studied in detail, the survey data will allow one to investigate its bright end and, possibly, to impose constraints on the maximum luminosity of ULXs.     

Two years of observations of the X-ray pulsar SMC X-1 with the ART-P telescope onboard the Granat observatory

We present the observations of the pulsar SMC X-1 with the ART-P telescope onboard the Granat observatory. We investigate the variability of the flux from the source on time scales of several tens of days. The intensity variation of the pulsar are shown to be consistent with the presence of a periodicity in the system with a characteristic time scale of ～61 days. The precession of an inclined accretion disk, as indirectly confirmed by the absence of low-state pulsations, may be responsible for the observed variability. The spectrum of the source is well described by a power-law energy dependence of the photon flux density with a slope of ～1.5 and an exponential cutoff at energies above ～14–18 keV. We estimated the inclinations between the planes of the orbit and the accretion disk and the magnetic field of the neutron star.     

Hard X-ray bursts detected by the IBIS telescope onboard the INTEGRAL observatory in 2003–2004

All of the observations performed with the IBIS telescope onboard the INTEGRAL observatory during the first one and a half years of its in-orbit operation (from February 10, 2003, through July 2, 2004) have been analyzed to find X-ray bursts. The time history of the IBIS/ISGRI total count rate in the energy range 15–25 keV revealed 1077 bursts of durations from ～5 to ～500 s with a high statistical significance (over the entire period of observations, only one event could be detected by chance with a probability of 20%). A part from the events associated with cosmic gamma-ray bursts (detected in the field of view or passed through the IBIS shield), solar flares, and activity of the soft gamma repeater SGR 1806-20, we were able to localize 105 bursts and, with one exception, to identify them with previously known persistent or transient X-ray sources (96 were identified with known X-ray bursters). In one case, the burst source was a new burster in a low state that received the name IGR J17364-2711. Basic parameters of the localized bursts and their identifications are presented in the catalog of bursts. Curiously enough, 61 bursts were detected from one X-ray burster, GX 354-0. The statistical distributions of bursts in duration, maximum flux, and recurrence time have been analyzed for this source. Some of the bursts observed with the IBIS/ISGRI telescope were also detected by the JEM-X telescope onboard the INTEGRAL observatory in the standard X-ray energy range 3–20 keV.     

A hard X-ray survey of the Galactic-Center region with the IBIS telescope of the INTEGRAL observatory: A catalog of sources

From August 23 through September 24, 2003, the INTEGRAL Observatory conducted a deep survey of the Galactic-Center region with a record-breaking sensitivity at energies above 20 keV. We have analyzed the images of the Galactic-Center region obtained with the ISGRI detector of the IBIS telescope (15–200 keV) and give a catalog of detected sources. We detected a total of 60 sources with fluxes above 1.5 mCrab, 44 and 3 of which were previously identified as binary systems of different classes in our Galaxy and as extragalactic objects, respectively. We discovered one new source.