Astronomy and Astrophysics Supplement Series

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List of Papers (Total 1,079)

CCD photometry of a δ Scuti variable in an open cluster - III. V 465 Persei in the α Persei cluster

We present the results of real-time CCD differential photometry for the δ Scuti variable V 465 Per. The observations were performed for thirteen nights between November, 1994 and January, 1995. Total 3345 points of differential V magnitudes were collected during the observation period of 76.4 hours. From the Fourier analysis, we have detected four frequencies as follows; f1=14...

Variation of spectral features in the ON2 water maser

Results are presented of the analysis of maser spectra in ON2, obtained with the RT-22 radio telescope at Pushchino during 1981–1996. The spectral features are analyzed and their time evolution examined. Anticorrelation between the fluxes of features with close radial velocities is found. A systematic displacement of the drifts sum of all features from 0.8 to during 1981–1988 and...

Structure detection in low intensity X-ray images

In the context of assessing and characterizing structures in X-ray images, we compare different approaches. Most often the intensity level is very low and necessitates a special treatment of Poisson statistics. The method based on wavelet function histogram is shown to be the most reliable one. We also present a multi-resolution filtering method based on the wavelet coefficients...

Direct demodulation technique for rotating modulation collimator imaging

Rotating modulation collimator (RMC) is an important imaging technique in hard X-ray astronomy. With traditional inversion techniques, the sensitivity, angular resolution and ability of simultaneous imaging of point sources and extended emission are not good enough in many practical cases. In this work, a new inversion technique, the direct demodulation method, is applied to...

B[e] stars - V. HD 50138 = MWC 158

On the basis of spectroscopic CCD material obtained at the Haute Provence Observatory, we provide line identifications and equivalent width measurements in the wavelength region 3738-10232 A of the spectrum of HD 50138 Over two hundred features are identified and a comparison of our results with those of other authors is provided. We also discuss the variability of the lines...

Catalogue of cataclysmic binaries, low–mass X–ray binaries and related objects (Sixth edition)

The catalogue lists coordinates, apparent magnitudes, orbital parameters, stellar parameters of the components and other characteristc properties of 318 cataclysmic binaries, 47 low–mass X–ray binaries and 49 related objects with known or suspected orbital periods together with a comprehensive selection of the relevant recent literature. In addition the catalogue contains a list...

Uniform approximation of planetary ephemerides

DE200/LE200 astronomical ephemerides are compressed finding the "best approximation” in the Chebyshev sense. When reproducing the data base from this polynomial approximation, the maxima and minima values of the error are equal in absolute value over the considered interval. In order to obtain polynomials valid also for a reliable evaluation at points interpolated on the data...

The visual line spectrum of AG Pegasi in 1995

Intermediate resolution observations of the blue spectrum of the symbiotic star AG Peg, being at a colliding wind stage in its evolution with decreasing luminosity and mass-loss rate of its hot component, have been realized. Profiles, fluxes and radial velocity data have been obtained. They are compared with earlier data, taken approximately at the same orbital phases. It turns...

A spatial user interface to the astronomical literature

We recall the properties of the Kohonen self-organizing feature map (SOM or SOFM), and explain how such maps can be used for information retrieval. We present an application to a bibliographic database. Our neural net can contain more than one level when necessary, which allows users to modify its spatial configuration. It is available for interactive use on the World-Wide Web...

A standard stellar library for evolutionary synthesis - II. The M dwarf extension

A standard library of theoretical stellar spectra intended for multiple synthetic photometry applications including spectral evolutionary synthesis is presented. The grid includes M dwarf model spectra, hence complementing the first library version established in Paper I (Lejeune et al. 1997). It covers wide ranges of fundamental parameters: : 50 000 K ~ 2000 K, : 5.5 , and : . A...

A 12CO () and () atlas of circumstellar envelopes of AGB and post-AGB stars

We present the results of a 12CO () and () survey on a sample of 46 objects classified as AGB and post-AGB stars. We have obtained fully sampled high resolution maps of their 12CO () emission by combining visibilities from the IRAM interferometer with short spacing observations from the IRAM 30 m telescope. Properties of their circumstellar envelopes like fluxes, radii, and...

A catalogue of Mg2 indices of galaxies and globular clusters

We present a catalogue of published absorp tion-line Mg2 indices of galaxies and glo bular clusters. The catalogue is maintained up-to-date in the HYPERCAT database. The measurements are listed together with the references to the articles where the data were published. A coded description of the observations is provided. The catalogue gathers 3541 measurements for 1491 objects...

A 1.4 GHz radio continuum and polarization survey at medium Galactic latitudes - I. Observation and reduction technique

A radio continuum survey at medium Galactic latitudes with the Effelsberg 100-m telescope is being carried out at a centre frequency of 1.4 GHz in total power and linear polarization. Areas up to of Galactic latitude are now being observed at a sensitivity of 15 mK in total intensity and 8 mK in linear polarization with an angular resolution of . This paper describes the...

Fabry-Perot filter based solar video magnetograph

A tunable Lithium Niobate (LiNbO3) Fabry-Perot filter (FP) (passband 165 mÅat 6122 Å) based video magnetograph has been designed and fabricated. This instrument is capable of providing near simultaneous observations of photospheric longitudinal magnetic field, chromospheric Hα , and photospheric CaI pictures using the same telescope and back-end set-up. The magnetic field...

Ionization balance for optically thin plasmas: Rate coefficients for all atoms and ions of the elements H to Ni

We present in this paper new and updated calculations of the ionization equilibrium for all the elements from H to Ni. We collected for these elements all the data available in the literature for the ionization and radiative plus dielectronic recombination rates. In particular, the dielectronic rates have been fitted with a single formula and the related coefficients are...

High X-ray-to-optical flux ratio RASS-BSC sources - I. The optical identification

We have used  (where c is count rate, and E stands for E magnitude from POSS) as an alternative expression for to study the X-ray-to-optical flux ratio distribution for known sources in ROSAT All Sky Survey Bright Source Catalog (RASS-BSC). Attention focuses on which classes of X-ray emitters have the highest X-ray-to-optical flux ratios. Then a high X-ray-to-optical flux ratio...

Hybrid mapping in VLBI and spurious symmetrization

The standard procedure used in hybrid mapping of VLBI data is examined. That this procedure can converge on wrong solutions has been pointed in the past by many authors. Walker (1996) indicated the bias in the resultant data due to the use of a point source as starting model. Bååth (1989) suggested the use of the original data set in each iteration of self calibration, and not...

Predicted HST FOC and broad band colours for young and intermediate simple stellar populations

This paper presents theoretical HST and broad band colours from population synthesis models based on an homogeneous set of stellar evolutionary tracks as computed under canonical (no overshooting) assumptions, covering the range of cluster ages from Myr to Gyr for three different metallicities (, 0.006, and 0.001). Statistical fluctuations in the cluster population have been...

Characterization of variable stars by robust wave variograms: An application to Hipparcos mission

Variogram analysis is applied to time series of variable stars. This method allows to characterize time-scales of varying signals. It is well suited for periodic and pseudo-periodic signals. The aspects of robustness, bin positions and bin widths for the variogram estimator are assessed, evaluated with the help of simulations and adapted to the Hipparcos photometry. For instance...

Extension of Tycho catalog for low-extinction windows in the galactic bulge

We present in this work secondary catalogs up to based on the Tycho reference frame (ESA, 1997) for 12 selected low-extinction fields towards the galactic bulge. The observations have been performed with the Askania-Zeiss Meridian Circle equiped with a CCD camera, located at the Abrahão de Moraes Observatory (Valinhos, Brazil) and operated by the Institute of Astronomy and...

Construction of the Tycho Reference Catalogue

The Tycho Reference Catalogue (TRC) project, as proposed in 1992 by the present authors, aimed to extend the Hipparcos reference system to fainter magnitudes. To assure rigidity of the reference system realization, the project relied on the Tycho Cataloguethat provides highly-accurate positions of more than one million stars on the Hipparcos system. To maintain the precision of...

Searching for non-gaussianity: Statistical tests

Non-gaussianity represents the statistical signature of physical processes such as turbulence. It can also be used as a powerful tool to discriminate between competing cosmological scenarios. A canonical analysis of non-gaussianity is based on the study of the distribution of the signal in the real (or direct) space (e.g. brightness, temperature). This work presents an image...

U B V absolute CCD photometry and differential astrometry of a sample of visual double stars with A-type primaries

We present V magnitudes, and colours of the components of 111 visual double stars and their relative position measurements ρ and θ. The primaries are of spectral class A; the angular separation is in the range. The observations were made at the 61-cm reflector of University of Toronto Southern Observatory, Chile. The obtained photometric results are of a moderate quality for...

Metallicity calibration of a DDO CN index and other low-resolution indices for G and K stars

Metallicity calibrations of low-resolution parameters are potentially useful for (at least) two problems: the properties of moving groups, and the supermetallicity problem in K giants. In this paper, metallicity calibrations are derived for six sets of parameters. One of these parameters is the DDO CN index δCN. This parameter and three others are calibrated for use with evolved...

The effective temperature scale of giant stars (F0–K5) - I. The effective temperature determination by means of the IRFM

We have applied the InfraRed Flux Method (IRFM) to a sample of approximately 500 giant stars in order to derive their effective temperatures with an internal mean accuracy of about 1.5% and a maximum uncertainty in the zero point of the order of 0.9%. For the application of the IRFM, we have used a homogeneous grid of theoretical model atmosphere flux distributions developed by...