Astrometric observations of major satellites of Saturn with a 26-inch refractor

The results of observations of Saturn and its satellites with the 26-inch refractor at Pulkovo are presented. Over the observing period from January 2008 until May 2009, results were found from more than 5000 CCD frames suitable for measurement. On the basis of these frames, 183 positions of major satellites of Saturn (with the exception of Mimas) were obtained. The astrometric reduction was based on the Turner method, with the use of the UCAC2 catalog as a reference. The obtained equatorial coordinates of satellites were compared with the TASS 1.7 theory, and results of comparison are presented. The accuracy of observed positions is 0.05″ on average. Positions of Saturn, calculated on the basis of positions of satellites and their theoretical saturnocentric coordinates according to the TASS 1.7, and the differential coordinates of satellites relative to each other, are also given.     

Astrometric study of the relative motion of three stars with possible invisible companions based on homogeneous series obtained at Pulkovo with a 26-inch refractor

We investigate the relative motion of three stars, ADS 7446, 9346, and 9701, based on long-term observations with the Pulkovo 26-inch refractor. The relative motion of all three stars shows a perturbation that could be produced by the gravitational influence of an invisible companion. For ADS 7446, we have determined the orbit of the photocenter with a period of 7.9 yr; the mass of the companion is more than 0.4M _⊙. For ADS 9346, we have determined the radial velocities of the components: −14.60 km s⁻¹ for A and −13.94 km s⁻¹ for B. For ADS 9346 and 9701, we have determined the dynamical parallaxes, 24 and 20 mas, respectively, which are larger than those in the Hipparcos catalog by 5 mas, and calculated the orbits by the apparent motion parameter (AMP) method. The new orbit of ADS 9346 is: a = 5″.2, P = 2035 yr, and e = 0.46 at the system’s mass M = 2.5M _⊙. The new orbits of ADS 9701 are: (a = 2″.9, P = 829 yr, e = 0.54, M = 4.3M _⊙) and (a = 3″.8, P = 1157 yr, e = 0.53, M = 5.0M _⊙).     

Astrometric CCD observations of visual double stars at the Pulkovo Observatory

We present the results of 3489 astrometric observations for 361 visual double stars performed in 2003–2007 with the 26-inch refractor of the Pulkovo Observatory. The angular separations between the components (ρ) and the position angles (θ) are given. The errors in these quantities are, on average, 0″.009 for ρ and 0°.40/ρ for θ, where ρ is the separation in arcseconds.     

Astrometric observations of Uranus with the Pulkovo Normal astrograph

The positions of Uranus were observed astrometrically with a CCD detector attached to the Pulkovo Normal astrograph (D/F = 0.33 m/3.5 m, S2C CCD, FOV 18′ × 16′). We provide the positions in the time interval from 2006 to 2011. Reduction of the CCD images was made with reference to the UCAC3 catalogue. The (O-C) values were calculated using the “Natural Satellites Service”. The results were compared with two contemporary theories of Uranus’s motion: INPOP10 and DE414/LE414. The obtained equatorial coordinates correspond well to both theories. On average, (O-C) over both coordinates relative to both theories are 0.1″.     

Astrometric studies of the results of a new reduction of old photographic observations of the Saturnian System based on the comparison with the modern theories of satellite motion

The paper shows the possibility of increasing the accuracy of the results of photographic observations of Saturn and its moons made in the 1970s and reduced using the old reference star catalogues and semiautomatic measurements. New celestial coordinates of the moons (from the third to the eighth), “satellite minus satellite” relative moon coordinates, and Saturn coordinates by positions of satellites are obtained without measuring its images. The results are stored in the Pulkovo Observatory database on the Solar System bodies and are available online at www.puldb.ru. The efficiency of the reduction method based on digitizing of astronegatives using 21 Mpx Canon digital camera and IZMCCD software is shown. The comparison of new results of old observations with the latest theories of moon motion has revealed a significant increase in satellite positioning accuracy. The investigation of the differences (O–C) of celestial coordinates from satellite positions in their apparent Saturn-centric orbits has revealed a noticeable motion of the differences (O–C) in right ascension depending on their distances from Saturn for all moons.     

The astrometric observations of planetary satellites, close approaches and occultations of stars by asteroids and mutual events in the systems of planetary satellites with the 26-in. refractor of Pulkovo observatory in 1995-2006

Astrometric and photometric observations of major planets, their satellites and asteroids have been made with the 26-in. refractor of the Pulkovo observatory during the period from 1995 to 2006. The CCD (ST6) and photographic observations were carried out. Accurate relative position of satellites of Jupiter and Saturn have been derived. The positions of Saturn have been calculated using the theoretically predicted coordinates of satellites relative to the planet without measurements of the photographic images of the planet. Also the observations of Hale-Bopp comet and Mercury transit have been made. The 26-in. refractor has been included into the international campaign PHEMU-2003: photometric CCD observations of mutual occultations and eclipses of Galilean satellites. The light curves of the events have been obtained and parameters of the events have been determined.     

Astrometric observations of the Uranian satellites with the Faulkes Telescope North in 2007 September

The results of astrometric observations of the main Uranian satellites taken with the Faulkes Telescope North are presented. A median filter algorithm was applied to subtract a scattered-light halo caused by Uranus. The Two-Micron All-Sky Survey (2MASS) and USNO-B1.0 were used as reference catalogues. The mean value of the differences between the equatorial coordinates of the satellites determined with 2MASS and USNO-B1.0 is close to 200 mas. A comparison of the observed equatorial coordinates of the satellites and their relative positions with ephemerides based on different combinations of theories of motion of Uranus and its satellites (DE405+GUST86, DE405+GUST06, INPOP+GUST86, INPOP+GUST06) was performed. The satellites' positions obtained with respect to 2MASS are in better agreement with theories. The values of (O−C) of the equatorial coordinates determined with the 2MASS are mainly less than 100 mas. The majority of (O−C) of relative positions are within ±50 mas. The mean values of the standard errors of (O−C) are within 20 to 60 mas.     

Meridian observations of solar system bodies with the struveertel instruments of the Pulkovo Observatory

Two Struve-Ertel instruments were used for the daytime observations of the Sun, Mercury, Venus and Mars at Pulkovo from 1956 to 1976. The FK4 equinox and equator corrections were derived. Both the instruments were installed in 1983–1986 at the Kislovodsk Station of the Pulkovo Observatory. The atmospheric dispersion and lateral refraction have been estimated at the Station.     

Speckle observations with PISCO in Merate – VII. Astrometric measurements of visual binaries in 2007

We present relative astrometric measurements of visual binaries made during the first semester of 2007, with the Pupil Interferometry Speckle camera and COronagraph (PISCO) at the 102-cm Zeiss telescope of Brera Astronomical Observatory, in Merate. Our sample contains orbital couples as well as binaries whose motion is still uncertain. We obtained 226 new measurements of 214 objects, with angular separations in the range 0.15–4.5 arcsec, and an average accuracy of 0.013 arcsec. The mean error on the position angles is     . Most of the position angles could be determined without the usual 180° ambiguity with the application of triple-correlation techniques and/or by inspection of the long integration files. We also present the new orbits we have computed for ADS 7871, 7982 and 8128, for which our measurements lead to large residuals and/or for which the revision is justified by the significant number of observations made since the publication of the previous orbit.     

Speckle observations with PISCO in Merate: VIII. Astrometric measurements of visual binaries in 2007 and new orbits of the multiple system Zeta Aqr

We present relative astrometric measurements of visual binaries made during the second semester of 2007, with the speckle camera PISCO at the 102 cm Zeiss telescope of Brera Astronomical Observatory, in Merate. Our sample contains orbital couples as well as binaries whose motion is still uncertain. We obtained 283 new measurements of 279 objects, with angular separations in the range 0″.17–4″.4, and an average accuracy of 0″.014. The mean error on the position angles is 0°.6. Most of the position angles were determined without the usual 180° ambiguity with the application of triple‐correlation techniques and/or by inspection of the long integration files. We also present the new orbit we have computed for Zeta Aqr AB (ADS 15971), for which our measurements lead to large residuals with the previously computed orbit. We were also able to compute the elements of the perturbation orbit Bb‐P caused by an invisible companion, whose mass is estimated at 0.7 M_⊙ (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Pulkovo astrometric observations of bodies in the Solar system from 1898 to 2005: Observational database

We provide an overview of the main results obtained as part of the programs for astrometric observations of bodies in the Solar system at the Pulkovo Observatory over the period 1898–2005. We summarize the results of photographic observations and show new possibilities for astrometric observations in connection with the transition to CCD detectors on Pulkovo instruments. Observing and data reduction techniques are considered. A database with Pulkovo observations of bodies in the Solar system has been created and opened to users. The database is accessible at http://www.puldb.ru.     

Astrometric results of observations of mutual occultations and eclipses of the Galilean satellites of Jupiter in 2002-2003

We suggest a new approach and develop an original method for deriving astrometric data from the photometry of mutual occultations and eclipses of planetary satellites. We decide to model not the relative apparent motion of one satellite with respect to another satellite but the deflection of the observed relative motion with respect to the theoretical motion implied by appropriate ephemerides.We have attempted to reduce the results of photometric observations of the Gallilean satellites during their mutual occultations and eclipses in 2002-2003. The data of observation for 319 light curves of 106 mutual events were received from the observers. The reliable 245 light curves were processed with our method. Eighty six apparent relative positions have been obtained.Systematic errors arise inevitably while deriving astrometric data. Most of them are due to factors that are unrelated to the methods for deriving astrometric data. The systematic errors are more likely due to incorrect excluding the effect of background on photometric counts. In the case of mutual occultations, the flux drop is determined to a considerable degree by the ratio of the mean albedos of the two satellites. Some mutual event observations revealed wrong adopted values of the mean albedos.     

An accuracy estimation of the World CCD asteroid observations in the years 1999-2005

The MPC database of the asteroid observations (each position from near 20 millions) was used in analysis of observational accuracy for more than 300 active world observatories both professional and amateur. The values of the “Mean error of a single observation” σ (for α,δ) were derived based on the Pulkovo method of accuracy estimation. These values may be used for observatory weight assignment in the orbital improvement procedures. The accuracy of the best amateur observations is proved to be comparable with professional one (σ=±0^″.20). The detailed results in electronic format are accessible from the first author.     

Mutual occultations and eclipses of the Galilean satellites of Jupiter in 1997: Astrometric results of observations

In 2006, a complete database of the international campaign on photometric observations of the Galilean satellites of Jupiter in the 1997 epoch of mutual occultations and eclipses was published. Only two thirds of the observations were considered by other authors beforehand. In this study, we have processed the whole observational database with an original technique in order to obtain the astrometric data. We determined 301 relative positions of the satellites from photometric observations performed at 50 observatories around the world. The results are put into a common database of all observations of the natural planetary satellites called the Natural Satellites Data Center (NSDC) available on the Internet site http://www.sai.msu.ru/neb/nss/index.htm. The influence of random and systematic errors on the accuracy of determining the coordinates of satellites has been analyzed. It has been shown that the largest systematic errors are caused by inaccurate elimination of the background of the photometric measurements and by the erroneous data on the albedo of satellites. The actual accuracy of astrometric results is 0.05″ and 0.07″ in right ascension and declination, respectively. New recommendations for photometric observations of satellites during the considered phenomena have been developed in order to avoid the systematic errors.     

CCD BVI photometry and Coravel observations of stars in the open cluster NGC 2489

We present CCD BVI photometry for the southern open cluster NGC 2489 and its surrounding field. The sample consists of 2182 stars measured in an area of 13.6 × 13.6 arcmin², extending down to   V ∼ 21.5  . These data are supplemented with CORAVEL radial-velocity observations for seven red giant candidates. A cluster angular radius of 6.7 ± 0.6 arcmin, equivalent to 3.5 ± 0.3 pc, is estimated from star counts carried out inside and outside the cluster region. The comparison of the cluster colour–magnitude diagrams with isochrones of the Padova group yields   E ( B − V ) = 0.30 ± 0.05, E ( V − I ) = 0.40 ± 0.05  and   V − M _V = 12.20 ± 0.25  for log   t = 8.70 ( t = 500⁺¹³⁰₋₁₀₀ Myr)  and   Z = 0.019  . NGC 2489 is then located at 1.8 ± 0.3 kpc from the Sun and 25 pc below the Galactic plane. The analysis of the kinematical data allowed us to confirm cluster membership for six red giants, one of them being a spectroscopic binary. A mean radial velocity of 38.13 ± 0.33 km s⁻¹ was derived for the cluster red giants. The properties of a sample of open clusters aligned along the line of sight of NGC 2489 are examined.     

Spectral and photographic studies of the known T association in the neighborhood of Cyg OB7

Spectral and photographic observations of an 11′×11′ region in the center of the known association Cyg OB7 are presented. The observations were made on the 2.6-m telescope of the Byurakan Astrophysical Observatory in 2004. The spectral camera SCORPIO, a multiregime focal reducer for the primary focus, was used. One new HH node and three new emission stars were discovered in the region under study. One of the previously known emission stars is found to have spectral class M0Ve and to lie at a distance of 200 pc. Some variability is detected in the brightness of a known infrared nebula and the cometary nebula CN2. __________ Translated from Astrofizika, Vol. 49, No. 3, pp.375–390 (August 2006).     

Relative astrometric and photometric measurements of visual binaries made with the Nice 76‐cm refractor in 2008

We present relative astrometric and photometric measurements of visual binaries made in 2008, with the 76‐cm refractor of Côte d'Azur Observatory. Our observing list contains orbital couples as well as binaries whose motion is still uncertain. Three different techniques were used for obtaining measurements: Lucky imaging, speckle interferometry and the Direct Vector Autocorrelation method. We obtained 2420 new measurements of the relative position of 2225 objects, with angular separations in the range 0″.07‐11″.5, and an average accuracy of 0″.02. The mean error on the position angles is 0°.6. We managed to observe faint systems (m_V ≈ 12) with large magnitude difference (up to Δm_V ≈ 5). We have thus been able to measure many systems containing red dwarf stars that had been poorly monitored since their discovery. We also measured the difference of magnitude of the two components of 376 objects with an estimated error of 0.1 mag. Finally, we provide a list of 33 newly discovered components of multiple or binary systems, which is a significant complement to our GII catalog (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Nucleosynthesis of26Al in the early solar system and in cosmic rays

The nucleus²⁶Al(^1/2 = 7.4 × 10⁵ yr) has long been considered as a possible heat source during the formation of the solar system. Recent experimental work has found no evidence for²⁶Al at the time of final solidification of the meteorites. Due to the short half-life these measurements do not rule out the possibility that²⁶Al was a significant heat source a few million years prior to final solidification. For²⁶Al to be an effective heat source in the early solar system it is necessary for the ratio²⁶Al/Si to be 2×10^–7 at the time of a solidification. The nucleosynthetic yields of²⁶Al by silicon burning, carbon burning, and spallation are discussed. It is shown that²⁶Al can be synthesized in carbon and/or silicon-burning supernovae. However, time scales in the early solar system make it more likely that²⁶Al, if present in planets, was synthesized by a proton irradiation in the early solar system. An integrated proton flux >4×10¹⁸ cm^–2 is shown to be necessary in order for²⁶Al to be a significant heat source. No conclusive evidence has been observed for an irradiation of this magnitude. Therefore, unless such evidence is found, it should be assumed that²⁶Alwas not involved in the formation of the solar system. In addition, the production of²⁶Al in cosmic rays is discussed and it is shown that either resolution of the Al isotopes in the cosmic rays or accurate measurements of the variation with energy of the cosmic ray abundance ratios Al/Si and Mg/Si can be used to determine the age of the cosmic rays, _C.R.. Current abundance data are extremely uncertain; however, the trend tends toward values of _C.R. 10⁶ yr.Supported in part by the National Science Foundation [GP-19887, GP-28027, GP-27304].