Astronomy and Astrophysics Supplement Series

https://aas.aanda.org/

List of Papers (Total 2,129)

Surface photometry of galaxies in low density regions

We perform detailed surface photometry, based on B- and/or R-band CCD images of 92 faint galaxies. They are a subsample of those galaxies which were studied by Hopp et al. (1994) in the direction of three nearby voids. We derive integral photometric parameters and radial surface brightness profiles and compare them to those of several faint galaxy samples, located in different...

Fractional abundances of molecules in dense interstellar clouds: A compendium of recent model results

In this paper we present calculated fractional abundances in dense interstellar clouds for selected atomic and molecular species using three different homogeneous, pseudo-time-dependent models discussed by Bettens, Lee, & Herbst (1995): the new standard model, the new neutral-neutral model, and model 4. We have run each model with 3 different hydrogen densities – 103, 104, and...

Multi-colour photometric and spectroscopic monitoring of the WN5 star EZ Canis Majoris

We present and analyse photometric and spectroscopic observations of the WN5 star EZ Canis Majoris obtained over a period of 7 years. We discuss the changing light curve, the shift in phase of the maxima and point to flare type variability seen in one night. Small amplitude variations are reported in another night. We have investigated the change of the average visual magnitude...

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...

Magnetic configuration of a sunspot region using the H line

The configuration of the magnetic field in an active region is analysed using a set of Hβ chromospheric magnetograms and narrow pass-band filtergrams taken at various positions on the line. We found that the chromospheric magnetic field is parallel to the chromospheric features and inhomogeneous. The photospheric magnetic field disappears abruptly in the edge of the penumbra; the...

UBVRI photometric monitoring of 7 rapidly rotating late-type dwarfs in the Alpha Persei cluster

The UBVRI light curves of 7 late-type dwarfs amongst the fastest rotators of the Alpha Per cluster (vsini ≥140 km s-1) are presented. The shape of the light curves suggests that the photometric variations are most often dominated by a single group of cool spots located at intermediate or high latitude on the stellar surface. Assuming that starspots are good tracers of the stellar...

A 15 years monitoring program at 408 MHz

This is the second paper based on the 408 MHz monitoring program with the East-West arm of the Bologna interferometer. The monitoring concerned 125 radio sources measured approximately once a month for 15 years. We present the summary of the variability analysis concerning all the sample and the monitoring data, not yet published, of the variable sources.

Light curves and periods of Mira variables

Good distance indicators are needed in studies of the galactic structure. Pulsating variables can be used, but the problem is to find a homogenous sample obeying a period-luminosity relation with low scatter. In this paper, we show how such a sample can be produced using the Terzan catalogue of Variables and available Schmidt plates. We have selected 150 large amplitude variables...

Optical structure and star formation in blue compact dwarf galaxies. I. Observations and profile decomposition

We present new B and R CCD surface photometry for a sample of 4 Blue Compact Dwarf Galaxies (BCDs) and 2 higher luminosity starburst galaxies. We find that the BCD surface brightness profiles (SBPs) can be generally well fitted by the sum of the light of 3 distinct components: 1) an exponential component at large radii, with or without a central flattening which describes the...

A spatial and spectral maximum entropy method as applied to OVRO solar data

We present first results of applying a Maximum Entropy Method (MEM) algorithm that acts in both the spatial and spectral domains to data obtained with the frequency-agile solar interferometer at Owens Valley Radio Observatory (OVRO) taken at 45 frequencies in the range . The traditional MEM algorithm does not exploit the spatial information available at adjacent frequencies in...

Absolute transition probabilities for the a6D y6P° multiplet (#8) of Fe II

We report the first laboratory measurement of absorption oscillator strengths (f-values) for 6 VUV () transitions of the multiplet (#8) in Fe II. We have also reconfirmed a recent measurement of the f-value of the Fe II resonance line at . These measurements are made with the high sensitivity absorption experiment at the University of Wisconsin-Madison. Measurements are also made...

TT Arietis: Photometric variability from 1985 to 1994

Results of photoelectric observations of TT Ari during the 1985–1994 interval are presented. Observations were carried out at the Rozhen and Belogradchik observatories as part of our programme for the study of anti-dwarf novae. The long-term light curve in the standard UBV system is constructed and peculiarities of the long-term behaviour of the star in this time interval are...

Multicolour deep CCD photometric study of the moderately young southern open star clusters NGC 3228, NGC 4103, NGC 5662 and NGC 6087

CCD observations in the U, B, V, R and I passbands have been used to generate colour-colour and deep colour-magnitude diagrams for the young open star clusters NGC 3228, NGC 4103,  NGC 5662 and NGC 6087. The sample consists of about 2000 stars reaching down to . The interstellar extinction across the face of the imaged cluster regions seems to be uniform with average values of...

The high energy instrument PDS on-board the BeppoSAX X–ray astronomy satellite

BeppoSAX/PDS experiment is one of four narrow field instruments of the BeppoSAX payload, that also includes two wide field cameras. The goal of PDS is to extend the energy range of BeppoSAX to hard X–rays. The operative energy range of PDS is 15 to 300 keV, where the experiment can perform sensitive spectral and temporal studies of celestial sources. The PDS detector is composed...

Two-band spectral filtering in instruments for measuring solar magnetic fields

In this paper we formulate the basic concept of a bichromatic image technique. Specific examples of its application are analyzed in the context of research into solar plasma characteristics by pinpointing its merits and demerits. Specialized requirements to the spectral devices are set forth, which may be summarized as: a) the presence of two nearby identical spectral passbands...

Mass determination of astrometric binaries with Hipparcos - I. Theory and simulation

The analysis of the observations of double stars made by the ESA satellite Hipparcos has involved a very specific processing to derive the relevant astrometric parameters. This required to distinguish between several categories of double stars according to the separation and orbital motion. We show that for close pairs with orbital period less than about 20 years, the concept of...

CLEAN and WIPE

Clean is a matching pursuit process which has two weak points: in situations of astrophysical interest, the "clean map

Optical positions and proper motions of radio stars

The optical positions of 31 radio stars were obtained with the 40 cm astrograph at Zô–Sè Section, Shanghai Observatory from 1985 to 1988. The observational positions and the proper motions of these radio stars in the FK5 system are given in this paper.

New theoretical yields of intermediate mass stars

We present theoretical yields of H, 4He, 12C, 13C, 14N, and 16O for stars with initial masses between 0.8 and 8 and initial metallicities , 0.004, 0.008, 0.02, and 0.04. We use the evolutionary tracks of the Geneva group up to the early asymptotic giant branch (AGB) in combination with a synthetic thermal-pulsing AGB evolution model to follow in detail the chemical evolution and...

Library of high and mid-resolution spectra in the Ca ii H & K, H∝, , Hβ, Na i D1, D2, and He i D3 line regions of F, G, K and M field stars

In this work we present spectroscopic observations centered in the spectral lines most widely used as optical indicators of chromospheric activity (, , Ca ii H & K, and He i ) in a sample of F, G, K and M chromospherically inactive stars. The spectra have been obtained with the aim of providing a library of high and mid-resolution spectra to be used in the application of the...

A stellar coronograph for the COME-ON-PLUS adaptive optics system - I. Description and performance

The detection of faint emissions very close to much brighter objects is required in several different fields of astrophysics, for example in the search for planetary disks. We present here a coronograph that we built to work with , the ESO adaptive optics system, high angular resolution being of key importance in allowing observations close to a central, occulted object. The...

Photometric CCD sequences for calibration of the ESO/SERC atlas

For calibration of ESO/SERC survey plates, photometric CCD sequences have been obtained for 10 ESO/SERC fields in the area and . The sequences contain B, V and R magnitudes for 117 galaxies and 162 stars with .

Active region effects on solar irradiance at Na I D lines

The possibility to detect solar oscillations in the low frequency domain depends crucially on the power contrast among the oscillation signal and other time dependent signals in the same frequency range. The signal to noise ratio is increased by our ability to understand and remove solar sources of noise. In measurements of the mean Doppler velocity shift of the integrated solar...

New variable stars in the globular cluster NGC 288

We report discovery of 3 new faint variables in the globular cluster NGC 288: 2 SX Phe stars and 1 contact binary. Both SX Phe variables are blue stragglers. The contact binary is located below cluster turnoff, slightly to the red of the main sequence. New photometry of 6 previously known variables is also presented. We note that 26 out of a total 43 SX Phe stars identified...

The Washington Double Star Catalog (WDS, 1996.0)

A major revision of the Washington Double Star (WDS) catalog containing data for the components of 78 100 systems is now available from the data centers and via the World Wide Web (http://aries.usno.navy.mil/ad/wds/).