Systematic Errors of High–Precision Photometric Catalogues

A very accurate imitation of Hipparcos and Tycho Hp, B _T, andV _T magnitudes was made using W, B, V, R magnitudes from the Tien Shan photometric catalogue. The calculated magnitudes were compared to the observed ones. It is shown that there are systematic differences between calculated and observed magnitudes. The systematic errors are supposed to be bound up with the sky scanning procedure on the Hipparcos satellite. Polynomials in powers of coordinates have been proposed to take into account the systematic errors. 6558 stars have been found to be appropriate high-precision photometric standards. This revised version was published online in July 2006 with corrections to the Cover Date.     

Joint Spectrophotometric Catalogue of the Sternberg State Astronomical Institute and Fessenkov Astrophysical Institute: The analysis of common stars

TheSpectrophotometric Catalogue of the Sternberg State Astronomical Institute contains 875 stars; 8 of them are standards.TheCatalogue of the Fessenkov Astrophysical Institute consists of 1123 stars. The data on the spectral energy distribution for about a half of these stars are published.A comparison of energy distribution data for 473 common stars in the range 3200–7600 Å was made. Calibration of Alpha Lyr from Hayes (1985) was used for all the stars of both catalogues.In difference of the previous publications the comparison includes much more stars and energy distribution data were corrected where necessary. The agreement between the corrected data is better than in the case of the earlier comparison. Reductional factors due to the instrumental effects were taken into account for 275 stars from theSternberg Institute Catalogue. These factors are in the limits 1.01–1.04 and their mean value is 1.03.The reductional factors for the stars from theFessenkov Institute Catalague are much larger: 1.06–1.12 with the mean 1.06–1.07. In this case the reduction factors were taken into account for all the stars of the catalogue except the brightest ones withV<2.0.The values of the differences between spectral energy distribution data for common stars in dependence of magnitude, spectral type, and wavelength are presented.     

VRI photometry of M67 for CCD standardization at 2.3m VBT

We present the results from CCD photometry in theV, R andI bands, of the ‘Dipper Asterism’ region of the open cluster M67 based on observations carried out at the prime focus of the 2.3 m Vainu Bappu Telescope of the Vainu Bappu Observatory, Kavalur. The CCD parameters like the system gain and the readout noise are measured using several flatfield frames taken through the standardI filter. The CCD chip is calibrated using the photometric standards in the field and linear colour transformation relations are derived. Also a few newVRI photometric measurements are reported for the members of the cluster.     

Analysis of Neckel and Chini standard stars in theUBVRI photometric system

This paper studies the list of 60 faint standard stars of Neckel and Chini (1980) in theUBVRI Johnson photometric system. These standards have been used due to the collaboration in the HIPPARCOS project of our department, but this work was made in parallel of this and the results were not used.We have re-reduced the standard stars using our own method of reduction from a large number of selected observations made at the Observatorio Astronómico Nacional and at the Centro Astronómico Hispano-Alemán, both at Calar Alto, Spain, and at the Observatorio del Roque de los Muchachos, La Palma Island, Spain.The reduction method used is explained and the results are given for the four colours used: (B-V),(U-B), (V-R), and (V-I), together with theV magnitude, that is, we have corrected many standard stars for each colour and magnitude. These results are supported with graphs where residual colour (o magnitude), is plotted against corresponding colour (or magnitude).Finally, our (V-R) and (V-I) results are compared to those of Tayloret al. (1989), with a good correspondence.Observations were made at Observatorio Astronómico Nacional and Centro Astronómico Hispano-Alemán, at Calar Alto, and in the Observatorio del Roque de los Muchachos at La Palma. This work was supported, in part, by the Comisión Interministerial de Ciencia y Tecnologia of Spain, under contract PB85-0017.     

Absolute calibration of solar radio flux density in the microwave region

The absolute calibration of solar radio flux density in the microwave region, which showed considerable discrepancies until 1966, has become completely uniform through international cooperative work. A complete history is described to avoid confusion, and correction factors are derived to convert the published values into absolute values for long series of routine observations. It is also shown that the most reliable calibration can be made by using a large pyramidal horn and by using sky and room temperature as calibration standards.Abbreviation of Stations for Table II, Figures 2 and 3 BERL Heinrich-Hertz-Institut, Berlin Adlershof - BORD The Observatory, the University of Bordeaux - GORK Radiophysical Research Institute, Gorky - HIRA Hiraiso Radio Observatory - HUAN Geophysical Institute of Peru, Huancayo - IRKU Irkutsk Radioastronomical Observatory - KIEL Radio Observatory, Kiel University - Radio Observatory, Kiel University - KSLV Kislovodsk Radioastronomical Observatory - MANI Manila Observatory - ONDR Ondejov Observatory - OTTA National Research Council, Ottawa - PENT Dominion Radioastronomical Observatory, Penticton - SANM Observatory of Cosmic Physics, San Miguel - SAOP Mackenzie University, Sao Paulo - SGMR Sagamore Hill Radio Observatory - SYDN University of Sydney - TOKO Tokyo Astronomical Observatory - TYKW Toyokawa Observatory, Nagoya University - UCCL Belgian Royal Observatory, Uccle     

Galactic model parameters for field giants separated from field dwarfs by their 2MASS and V apparent magnitudes

We present a method which separates field dwarfs and field giants by their 2MASS and V apparent magnitudes. This method is based on spectroscopically selected standards and is hence reliable.We applied it to stars in two fields, SA 54 and SA 82, and we estimated a full set of Galactic model parameters for giants including their total local space density. Our results are in agreement with the ones given in the recent literature. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Tungsten isotopes in bulk meteorites and their inclusions—Implications for processing of presolar components in the solar protoplanetary disk

We present high precision, low‐ and high‐resolution tungsten isotope measurements of iron meteorites Cape York (IIIAB), Rhine Villa (IIIE), Bendego (IC), and the IVB iron meteorites Tlacotepec, Skookum, and Weaver Mountains, as well as CI chondrite Ivuna, a CV3 chondrite refractory inclusion (CAI BE), and terrestrial standards. Our high precision tungsten isotope data show that the distribution of the rare p‐process nuclide ¹⁸⁰W is homogeneous among chondrites, iron meteorites, and the refractory inclusion. One exception to this pattern is the IVB iron meteorite group, which displays variable excesses relative to the terrestrial standard, possibly related to decay of rare ¹⁸⁴Os. Such anomalies are not the result of analytical artifacts and cannot be caused by sampling of a protoplanetary disk characterized by p‐process isotope heterogeneity. In contrast, we find that ¹⁸³W is variable due to a nucleosynthetic s‐process deficit/r‐process excess among chondrites and iron meteorites. This variability supports the widespread nucleosynthetic s/r‐process heterogeneity in the protoplanetary disk inferred from other isotope systems and we show that W and Ni isotope variability is correlated. Correlated isotope heterogeneity for elements of distinct nucleosynthetic origin (¹⁸³W and ⁵⁸Ni) is best explained by thermal processing in the protoplanetary disk during which thermally labile carrier phases are unmixed by vaporization thereby imparting isotope anomalies on the residual processed reservoir.     

The Contribution of Sound Waves and Instabilities to the Penetration of the Solar Differential Rotation Below the Convection Zone

The response of a layer to a horizontal shear flow at its top the surface was studied numerically as an initial value problem. The geometry was Cartesian and the conservation equations were solved with the help of the Zeus-3D code. In the initial state, the pressure, p, and density, ρ, of the layer were assumed to be related by a polytropic equation of index 1.14, which best approximates the solar values in the region of interest. The values of p and ρ at the lower boundary of the layer, namely r=R _l=0.4 R _⊙, were taken to be the solar values. The upper boundary was chosen to be the base of the solar convection zone, r=R _c=0.7 R _⊙. The shear flow at the surface, v _φ(R _c), was proportional to the solar differential rotation, and acoustical oscillations were present in the layer. It is shown that if the initial state is stable, a dynamical coupling between sound waves and the shear flow transmits the surface flow to the inner regions of the layer, even in the absence of dissipation. The shear flow in the sublayer below the one at the surface is proportional to v _φ(R _c), to the time, and to the strength of the oscillations. The constant of proportionality is calculated from the numerical integrations, performed for times of the order of 100 hr. Extrapolation of these results to longer times shows that the surface shear flow is transmitted to the inner regions in a time of the order of of 30 000 years. If the initial state is unstable to the vertical shear, the region of maximum instability depends also on the horizontal shear, and is located away from the equator (where the vertical shear is maximum). As a consequence, the longitudinal flow below the surface shows two equidistant maxima across the equator, located at intermediate latitudes.     

New times of the minima and light elements of SW Lacertae

SW Lacertae is a short-period variable star of the W UMa-type. A total of 261 photoelectric observations for eachU, B, andV filter were obtained in 1986 while 522 photoelectric observations for eachB andV filter were obtained in 1987. All these observations were transformed to theU, B, andV colours of theUBV standard system. Nine light curves for primary and secondary eclipses were obtained, their times of minima were determined and a new linear ephemeris was obtained. The period changes of the system were also discussed.     

Refinement of the geopotential scale factorR 0 on

Altimetric measurements of the GEOSAT satellite were used for the determination of geopotential scale factorR ₀. The geopotential valueW ₀ on the geoid surface was then computed (W ₀ =GM/R ₀).The GEOSAT Geophysical Data Records (GDR's) covering an initial period of the Exact Repeat Mission (ERM) were filtered and processed. The necessary corrections were made in order to allow a precise detection of the sea surface. Gravitational geopotential, rotation and permanent tides were taken into account and the equipotential surface which is the best approximation of the sea surface was found.The determination of the potential valueW ₀ on the mean geoid surface in this way is very promising. An associated value withW ₀ - the geopotential scale factorR ₀ - seems to be a very good Earth dimension defining quantity. Moreover, there are many possible applications ofW ₀ (R ₀) in modern geophysics.The incorporation of one of these parameters - we now recommendR ₀ - into the set of the Primary Geodetic Parameters (PGP) is discussed and suggested.     

The visual surface brightness method and the radii of dwarf Cepheids

In order to determine the radii of dward Cepheids by applying the visual surface brightness method, the empirical relationship betweenF _V and (b–y) was derived. Seventeen stars of spectral type A to F where both angular diameters anduvby photometric data are available were selected from the literature. A theoretical [F _V , (b–y)] relation was derived by using the Kurucz model atmospheres. It was found that the theoretical relation is strongly dependent upon metallicity and surface gravity. To demonstrate that the visual surface brightness method is an effective way to determine the radii of dwarf Cepheids, both theoretical and empirical relations were applied to seven dwarf Cepheids. The most reliable result was obtained for AD CMi where the quality of the radial velocity data is superior.     

UBV photometry of AW Pegasi

NewUBV observations of the classical Algol system AW Peg were presented. The photometric minima times were collected and used together with the new determinations in a period study. No sign of any period change was found from observations covering more than sixty years. TheB andV light curves are analyzed by means of the Wilson-Devinney approach. It was verified that the system is semi-detached with a Roche lobe filling secondary.     

Light Curves of Selected Comets: Photometric Parameters and Flares

The light curves of four comets were constructed and analyzed. The photometric parameters H _yand nwere determined. The derived values of H _yand nwere compared with those obtained by other authors. The parameter nfor Comet Ikeya–Secchi was found to vary. A list of flares in these comets was compiled.     

The dependence of solar flare energetics on flare volumes

Solar X-ray flare images from Skylab and data from full Sun detectors were used in a statistical analysis to determine the relationship between flare volumes and flare energetics. Data from the rise phases of 45 flares were used in the analysis. For each event the diameter D, length L, and volume V of the flare loops were determined and then compared to the thermal energy, rate of increase of thermal energy, and rise time of the soft X-ray flux. The latter three quantities were all found to be positively correlated with D, L, and V. However, the thermal energy per unit volume and rate of increase of thermal energy per unit volume decrease with increasing volume. No correlation was found between emission measure Y and volume V, indicating that the electron density tends to be smaller for larger flare volumes. We find a larger dynamic range for V than for Y, hence knowledge of V is more critical than that of Y for calculating the thermal energy of the X-ray emitting structure, which is proportional to Y ^0.5 V ^0.5. Using certain assumptions, the results were compared to several flare models. The classical neutral sheet model, the sheared loop model of Spicer and even models using the magnetic field in a passive role for the energy release were all found to be consistent with the results.     

UBV Photometric Study of the Eclipsing Binary DM Delphini

The near-contact system DM Del with an A2V primary and a G8 secondary was observed in U, B and V wavelengths in July 1998. A new seasonal light curve is presented and a new observed time of minimum is given. The unperturbed part of the light curve was used to determine some basic parameters of the system with the Wilson-Devinney code, some of which were kept fixed for spot modelling of the light curves. A simple spot distribution was determined, based on a model with two cool spots on the surface of the secondary. Absolute elements were calculated and the evolutionary status was determined. This revised version was published online in July 2006 with corrections to the Cover Date.     

Light variation of the variable star OO Aquilae

PhotoelectricB andV observations of the W UMa-type system OO Aql have been obtained for 11 nights during the period from 22 June–30 July, 1987. A total of 978 observations were obtained in eachB andV filter. All these observations were transformed to theB andV colours of theUBV standard system. Five light curves for primary and secondary eclipses were obtained, its times of minima were determined and a new linear ephemeris was given. The period changes of the system were discussed.     

The photospheric abundance of iron

The center-to-limb variation of equivalent widths of 198 Fei lines in the spectral region 5500 to 7000 Å was studied with five photospheric models. The gf-values of Corliss and Warner (1964) were used in the analysis. The photospheric iron abundance was found to vary with excitation potential. This can be explained by a systematic error in the gf-values of high excitation lines and an error of 250 to 500K in the temperature of the arcs used for measuring the gf-values. Departures from LTE in the solar Fei lines are also a possibility. The adopted photospheric abundance of iron, log(N _Fe/N _H) is - 5.2.     

Delivery of icy planetesimals to inner planets in the Proxima Centauri planetary system

The estimates of the delivery of icy planetesimals from the feeding zone of Proxima Centauri c (with mass equal to 7m_E, m_E is the mass of the Earth) to inner planets b and d were made. They included the studies of the total mass of planetesimals in the feeding zone of planet c and the probabilities of collisions of such planetesimals with inner planets. This total mass could be about 10–15m_E. It was estimated based on studies of the ratio of the mass of planetesimals ejected into hyperbolic orbits to the mass of planetesimals collided with forming planet c. At integration of the motion of planetesimals, the gravitational influence of planets c and b and the star was taken into account. In most series of calculations, planetesimals collided with planets were excluded from integrations. Based on estimates of the mass of planetesimals ejected into hyperbolic orbits, it was concluded that during the growth of the mass of planet c the semi-major axis of its orbit could decrease by at least a factor of 1.5. Depending on possible gravitational scattering due to mutual encounters of planetesimals, the total mass of material delivered by planetesimals from the feeding zone of planet c to planet b was estimated to be between 0.002m_E and 0.015m_E. Probably, the amount of water delivered to Proxima Centauri b exceeded the mass of water in Earth's oceans. The amount of material delivered to planet d could be a little less than that delivered to planet b.     

Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system

The Pulkovo Compilation of Radial Velocities (PCRV) has been made to study the stellar kinematics in the local spiral arm. The PCRV contains weighted mean absolute radial velocities for 35 495 Hipparcos stars of various spectral types and luminosity classes over the entire celestial sphere mainly within 500 pc of the Sun. The median accuracy of the radial velocities obtained is 0.7 km s^?1. Results from 203 publications were used in the catalogue. Four of them were used to improve the radial velocities of standard stars from the IAU list. The radial velocities of 155 standard stars turned out to be constant within 0.3 km s^?1. These stars were used to analyze 47 768 mean radial velocities for 37 200 stars from 12 major publications (～80% of all the data used). Zero-point discrepancies and systematic dependences on radial velocity, B-V color index, right ascension, and declination were found in radial velocity differences of the form “publication minus IAU list of standards.” These discrepancies and dependences were approximated and taken into account when calculating the weighted mean radial velocities. 1128 stars whose independent radial-velocity determinations were available at least in three of these publications and agreed within 3 km s^?1 were chosen as the work list of secondary standards. Radial-velocity differences of the form “publication minus list of secondary standards” were used by analogy to correct the zero points and systematic dependences in the radial velocities from 33 more publications (～ 13% of the data used). In addition, the radial velocities from 154 minor publications (～7% of the data used) pertaining to well-known instruments were used without any corrections.     

A High Order Perturbation Analysis of the Sitnikov Problem

The Sitnikov problem is one of the most simple cases of the elliptic restricted three body system. A massless body oscillates along a line (z) perpendicular to a plane (x,y) in which two equally massive bodies, called primary masses, perform Keplerian orbits around their common barycentre with a given eccentricity e. The crossing point of the line of motion of the third mass with the plane is equal to the centre of gravity of the entire system. In spite of its simple geometrical structure, the system is nonlinear and explicitly time dependent. It is globally non integrable and therefore represents an interesting application for advanced perturbative methods. In the present work a high order perturbation approach to the problem was performed, by using symbolic algorithms written in Mathematica. Floquet theory was used to derive solutions of the linearized equation up to 17th order in e. In this way precise analytical expressions for the stability of the system were obtained. Then, applying the Courant and Snyder transformation to the nonlinear equation, algebraic solutions of seventh order in z and e were derived using the method of Poincaré–Lindstedt. The enormous amount of necessary computations were performed by extensive use of symbolic programming. We developed automated and highly modularized algorithms in order to master the problem of ordering an increasing number of algebraic terms originating from high order perturbation theory.