Astronomy and Astrophysics Supplement Series

https://aas.aanda.org/

List of Papers (Total 1,079)

FARGO: A fast eulerian transport algorithm for differentially rotating disks

We present an efficient and simple modification of the standard transport algorithm used in explicit eulerian fixed polar grid codes, aimed at getting rid of the average azimuthal velocity when applying the Courant condition. This results in a much larger timestep than the usual procedure, and it is particularly well-suited to the description of a Keplerian disk where one is...

A deep echelle survey and new analysis of diffuse interstellar bands

We report a deep survey of diffuse interstellar bands (DIBs) between 3906 Å and 6812 Åunder consistent observing conditions toward three very reddened and five unreddened stars. BD+63° 1964's line-of-sight was shown to present exceptional DIB enhancement in number as well as in strength. The early spectral type of the star and the use of spectra of an unreddened comparison star...

Search and discovery tools for astronomical on-line resources and services

A growing number of astronomical resources and data or information services are made available through the Internet. However valuable information is frequently hidden in a deluge of non-pertinent or non up-to-date documents. At a first level, compilations of astronomical resources provide help for selecting relevant sites. Combining yellow-page services and meta-databases of...

Optical surface photometry of radio galaxies - II. Observations and data analysis

Optical imaging observations for 50 radio galaxies are presented. For each object isophotal contours, photometric profiles, structural parameters (position angle, ellipticity, Fourier coefficients), and total magnitudes are given. These observations, obtained in the Cousins R band, complement the data presented in a previous paper and are part of a larger project aimed at...

Polarization for pair annihilation in strong magnetic fields

We derive the cross-section for one-quantum annihilation of polarized electrons and positrons. The electron and positron can occupy arbitrary Landau levels and have non-zero momentum parallel to the field, and the cross-section is calculated for any polarization of the radiation. When we take zero parallel momentum for the electron and sum over photon polarization we obtain...

Modeling the imaging process in optical stellar interferometers

Optical interferometers on the ground, like ESO's Very Large Telescope Interferometer (VLTI) and the Keck Interferometer, and in space, like the InfraRed Space Interferometer (IRSI/Darwin) and the Space Interferometry Mission (SIM), will bring a major breakthrough in optical and near-infrared high angular resolution astronomy at the beginning of the next millennium. These...

CCD photometric study of the contact binary FG Hydrae

A new light curve of the contact binary FG Hya is presented in this paper. The new light curve and those obtained by other authors from 1955 to 1985 show the change in the shape of the light curves of the system. The difference in the depths between the primary and secondary eclipses increased yearly from 1955 to 1985, but the present light curve seems to exhibit the same shape...

The ATESP radio survey - II. The source catalogue

This paper is part of a series reporting the results of the Australia Telescope ESO Slice Project (ATESP) radio survey obtained at 1400 MHz with the Australia Telescope Compact Array (ATCA) over the region covered by the ESO Slice Project (ESP) galaxy redshift survey. The survey consists of 16 radio mosaics with resolution and uniform sensitivity ( noise level ~79 μJy) over the...

Blind source separation and analysis of multispectral astronomical images

Celestial sources are studied by means of multispectral analysis, for which a pixel value can be considered as a mixture of different sources. We show that the application of blind source separation methods can display interesting features, which can help astronomers to improve their description of celestial sources. Experiments were carried out on Hubble Space Telescope images...

CCD photometric search for peculiar stars in open clusters - I. NGC 2169, Melotte 105 and NGC 6250

The search for chemically peculiar (CP) stars in open clusters using photoelectric photometry sampling the presence of the characteristic flux depression feature at 5200 Å via the -system (Maitzen 1976) has so far delivered data for objects usually no more distant than 1000 pc from the Sun. A series of fourteen papers (first: Maitzen & Hensberge 1981; for the time being last...

Determination of effective temperatures for an extended sample of dwarfs and subdwarfs (F0-K5)

We have applied the InfraRed Flux Method (IRFM) to a sample of 475 dwarfs and subdwarfs in order to derive their effective temperatures with a mean accuracy of about 1.5%. We have used the new homogeneous grid of theoretical model atmosphere flux distributions developed by Kurucz (1991, 1993) for the application of the IRFM. The atmospheric parameters of the stars cover, roughly...

CCD spectrophotometry of CVs. III. 3270-9000 Å atlas for 38 faint systems

A 7 Å resolution, 3270-9000 Å spectrophotometric atlas is presented for 38 objects from the Downes & Shara (1993) catalogue of Cataclysmic Variables (CVs). The stars were selected among those listed as lacking published spectra. As for previous papers in this series, the aim is to check the CV status of the objects spectroscopically and to provide high quality absolute...

New weak-line T Tauri stars in Orion from the ROSAT all-sky survey

We present results of the spectroscopic and photometric follow-up observations of the ROSAT all-sky survey in the direction of the Orion cloud complex. The main goal of these observations is the search for X-ray emitting pre-main sequence stars. 820 X-ray sources were detected with high confidence in about 450 square degrees. The mean density of X-ray sources in this region is a...

A CCD BVI color-magnitude study of the metal-rich globular cluster NGC 5927

We present for the globular cluster NGC 5927 the first multicolor CCD photometry that reaches below the cluster's main sequence turnoff. The turnoff is located approximately at , , . There is a hint of horizontal branch morphology variations with distance from the cluster center. Using the isochrones of VandenBerg & Bell (1985), we derive the cluster age to be about 15 Gyr.

Catalogue of solar type II radio bursts observed from September 1990 to December 1993 and their statistical analysis

Solar type II radio bursts represent the radio signature of shock waves travelling through the solar corona. They are associated with flares, coronal mass ejections (CME's) and interplanetary shocks. Type II radio bursts appear as emission stripes slowly drifting from high to low frequencies in dynamic radio spectra. The spectral features of all solar type II radio bursts...

NTT V, I colour-magnitude diagrams of the bulge globular cluster Tonantzintla 2

Ton 2 is among the less-known Galactic globular clusters. We present for the first time colour magnitude diagrams in the V, I bands. We used the ESO NTT telescope under an excellent seeing of 0.6″. The horizontal branch is red and close to the red giant branch, tilted by some differential reddening. The horizontal branch morphology and the red giant branch curvature suggest a...

Cold neutral gas associated with the Gum nebula

Based on HI maps covering the 3 600 square degrees area delimited by , we investigated the neutral hydrogen distribution in the Gum nebula and its environments. The main result is the appearence of a huge disk of neutral gas at a kinematical distance compatible with that of the nebula, and whose angular dimensions coincide with the optical image of the Gum nebula. The disk...

Updating standard solar models

We present an updated version of our standard solar model (SSM) where helium and heavy elements diffusion is included and the improved OPAL equation of state (Rogers 1994; Rogers et al. 1996) is used. In such a way the EOS is consistent with the adopted opacity tables, from the same Livermore group, an occurrence which should further enhance the reliability of the model. The...

A sample of galaxy clusters to study the fundamental plane: Redshift measurements

We present the results of spectroscopic observations of galaxies in a sample of nearby clusters. We measured galaxy redshifts and estimated cluster velocity dispersions. These observations were carried out at the Observatoire de Haute Provence as part of a program aiming at a more detailed study of the Cluster Fundamental Plane.

A new strategy for helioseismic inversions

Helioseismic inversion techniques have been revealed as powerful tools for inferring the internal structure and dynamics of the Sun. One of the most popular techniques is Regularized Least Squares. When it is used, it is necessary to define an inversion mesh and a penalty function, without an a priori knowledge of the behaviour of the solution. In addition, this penalty function...

Deep morphologies of type I planetary nebulae

Deep narrow band interference filters observations are presented for 7 type I galactic planetary nebulae (PNe). Except for the nearly circular planetary nebula A 39, the observations show overall dimensions appreciably larger than those quoted so far. The observed PN (NGC 6302 excepted) could have linear diameters larger than 1 pc. Our new observations imply ionized masses often...

Radial velocities and spectrophotometric properties of southern binary galaxies

We present spectrophotometry of a sample of 26 Southern binary galaxies 17 pairs were confirmed to be physically associated with typical separation of . Pairs with velocity difference are probably not physically bound. A comparison with field galaxies suggests that galaxies in pairs tend to have a younger population probably stimulated by tidal interaction. No correlation between...

Atomic data from the IRON Project - XXIV. Electron excitation of Li-like Fe xxiv between the n = 2 and = 2, 3, 4 fine-structure levels

Collision strengths for electron induced transitions in Li-like Fe xxiv are calculated using a Breit-Pauli R-matrix technique. The target has 15 fine structure states corresponding to . Autoionizing resonances are found to affect 18 of the 39 collision strengths, namely those for transitions where The present calculation is carried out only for electrons incident on the ground...

Multiwavelength observations of the field HS 47.5/22 in Ursa Major - I. The X–ray catalogue of a medium deep ROSAT survey

We present the X–ray source catalogue obtained from a ROSAT survey in the HQS field HS 47.5/22. The survey consists of 48 overlapping PSPC pointings which were first analysed individually, and then merged to increase the sensitivity. Both modes bring forth sources missed in the other, showing that both are necessary to detect all X–ray sources in the field. The final catalogue...

The observed periods of Ap and Bp stars

A catalogue of all the periods up to now proposed for the variations of CP2, CP3, and CP4 stars is presented. The main identifiers (HD and HR), the proper name, the variable-star name, and the spectral type and peculiarity are given for each star as far as the coordinates at 2000.0 and the visual magnitude. The nature of the observed variations (light, spectrum, magnetic field...