Astronomy and Astrophysics Supplement Series

https://aas.aanda.org/

List of Papers (Total 1,079)

Three stage period analysis and complementary methods

We generalize the multistage period search and analysis method for the case when the data error estimates (i.e. statistical weights) are available. Adjustment of model parameters allows us to detect complex wave forms in noisy data. Complementary statistical tests are also presented to estimate the significance of the detected periodicities, to verify the modelling reliability...

Extraction of a deterministic component from ROSAT X-ray data using a wavelet transform and the principal component analysis

In the present work wavelet transform methods together with principal component analysis and non-linear filtering are used to extract the deterministic components in AGN X-ray variability from the photon event history files. The photon history files are converted into so called ampligrams using the Morlet wavelet transform. The ampligram may be considered as an analogy to signal...

Accuracy of radial-velocity measurements for early-type stars - I. Spectral-type mismatch in A-type synthetic spectra

Measuring accurate radial velocities of rotating early-type (O-B-A) stars using cross-correlation techniques is hampered by the fact that object-template spectrum mismatch causes systematic errors that do not cancel out sufficiently in these spectra. This series of papers aims at quantifying those mismatch errors, understanding their astrophysical origin, and developing...

Galaxy coordinates - II. Accurate equatorial coordinates for 17298 galaxies

Using images of the Digitized Sky Survey we measured coodinates for 17298 galaxies having poorly defined coordinates. As a control, we measured with the same method 1522 galaxies having accurate coordinates. The comparison with our own measurements shows that the accuracy of the method is about 6 arcsec on each axis (RA and DEC).

Dense molecular gas in Seyfert galaxies

We have used the 20 m Onsala and 15 m SEST telescopes to observe the CO  (simultaneously with CO  at SEST) and HCN   (simultaneously with CS  at SEST) transitions in 20 Seyfert galaxies. The sample consists of the 18 galaxies detected in CO  by Heckman et al. (1989) plus 2 which were not detected in their survey. We have successfully detected all of the galaxies in the CO...

1.65 μm (H-band) surface photometry of galaxies - IV. observations of 170 galaxies with the Calar Alto 2.2 m telescope

We present near-infrared (H band) surface photometry of 170 galaxies, obtained in 1997 using the Calar Alto 2.2 m telescope equipped with the NICMOS3 camera MAGIC. The majority of our targets are selected among bright members of the Virgo cluster, however galaxies in the A262 and Cancer clusters and in the Coma/A1367 supercluster are also included. This data set is aimed at...

Spectral classification of O–M stars on the basis of UBV photometry

A new technique allowing the Q-method to be used surely for both the spectral classification of young O–A0 stars and older spectral subclasses A1–M5 is described. Characteristics of interstellar light absorption dependence on distance in the given direction of the sky is used as a main criterion for excluding possible multiplicity of star spectral estimates at some constant...

Proper motions of Luyten Catalogue stars with declinations between -5° and -30° and right ascensions between 13h 30m and 24h

Proper motions, coordinates and finding charts are given for 166 Luyten Catalogue (LTT, Luyten 1957) stars re-discovered as a result of a search for high proper motion stars carried out in nineteen 5 areas, located between and in declination and between 13h 30m and 24h in right ascension. An estimated precision level between 8 and 19 mas/year was achieved for the proper motions...

Atomic data from the IRON Project - XLII. Electron impact excitation of Fe xxi

Collision strengths and collisional rate parameters are provided for transitions among the and 2p levels of C-like Fe xxi. The data have been computed in a 52-state Breit-Pauli approximation thus accounting for the most prominent relativistic effects. An R-matrix close-coupling calculation comprising partial wave contributions up to and of order 8000 energy points in the range up...

CCD photometry and proper motions of late–type stars in the young open cluster Stock 2

We present the results of the first CCD BVRI photometric and proper motion study of late-type stars in the young open cluster Stock 2.
Twenty–one fields of approximately size have been observed photometrically, from which we have identified 118 candidate members based on their positions on colour–magnitude diagrams relative to theoretical isochrones. From a comparison of the...

Dust properties in NGC 6611

An investigation on dust properties in the NW portion of NGC 6611 has been conducted polarimetrically to test the existence of abnormal extinction in that section of the open cluster in an independent way.
As previously suggested for the η Carinae nebula by Tapia et al. (1988b) and subsequently confirmed by Marraco et al. (1993), the canonical relation between and (the wavelength...

Optical spectroscopy of galaxies in the direction of the Virgo cluster

Optical spectroscopy of 76 galaxies, 48 of which are projected in the direction of the Virgo cluster and 28 onto the Coma–A1367 supercluster, is reported. Adding these new measurements to those found in the literature, the redshift completeness in the Virgo region becomes 92% at and 68% at . The one of CGCG galaxies in the direction of the Coma–A1367 supercluster becomes 98%. The...

GAIA: Global astrometric interferometer for astrophysics

GAIA is a preliminary concept for an astrometric mission, recently recommended within the context of ESA's `Horizon 2000 Plus

The chemical composition towards the Galactic anti-centre. I. Observations and model atmosphere analyses

High resolution spectra of six early B-type main-sequence stars having galactocentric distances of between 10 and 18 kpc are presented. We list the equivalent widths for the metal lines and illustrate their hydrogen and helium line profiles. The stars are analysed using LTE line-blanketed model atmosphere techniques to derive atmospheric parameters and surface chemical...

The ellipticities of globular clusters in the Andromeda galaxy

The projected ellipticities and orientations of 173 globular clusters in the Andromeda galaxy have been determined by using isodensity contours and 2D Gaussian fitting techniques. A number of B plates taken with the 2 m Ritchey-Chretien-coud reflector of the Bulgarian National Astronomical Observatory were digitized and processed for each cluster. The derived ellipticities and...

Understanding radio polarimetry. I. Mathematical foundations

The measurement of polarized radiation uses entirely different methods at optical and radio wavelengths. As a result, the algebraic analysis of polarimeter performance differs and, in the case of radio interferometry, is unnecessarily complicated. We demonstrate that the mathematical operation of outer matrix multiplication provides the missing link between the two approaches...

Contribution à l'étude des binaires des types F, G, K, M. VII. HD 147395, une géante M binaire spectroscopique

HD 147395, a giant M2 star, was found to be a spectroscopic binary by the Mount Wilson astronomers some time ago, but its orbit remained unknown so far. Radial velocity observations carried out at the Observatoire de Haute-Provence with the CORAVEL spectrovelocimeter permitted us to obtain the orbital elements of this binary. They are as follows: P = 335.537 days; T = 4448335.0...

Transition probabilities for [Ni I] and [Ni II] lines

New radiative transition probabilities have been calculated for forbidden lines of astrophysical interest in Ni I and Ni II. The accuracy of the transition probability scales is established on the basis of two independent calculations performed with the approximately relativistic Hartree-Fock and SUPERSTRUCTURE codes. Both physical models take into account the most important...

Long-term monitoring of active stars. V. photometry collected in Feb.-Mar. 1990

High-precision UBV(RI)c photometry of 12 selected active stars, collected at the European Southern Observatory (La Silla, Chile) over the period February - March 1990, is presented. Significant evolution of the light curves, period variations and, in most cases, evidence for long-term variability of the global degree of spottedness are found. Some of the spectral classifications...

Monitoring of 3C 66A during an extended outburst. I. The light curves

We present results from a two year intensive monitoring of BL Lac object 3C 66A (PKS 0219+428). This object was observed in outburst during these two years. It reached the brightest ever observed magnitude on V=13.59 (1.2.1995) and on K=10.59 (15.2.1994). The optical and infrared light curves are characterised by randomly distributed fast flares, lasting a few days and well...

The high pressure gas scintillation proportional counter on-board the BeppoSAX X-ray astronomy satellite

In this paper we describe the High Pressure Gas Scintillation Proportion Counter, one of the Narrow Field Instrument of the X–ray astronomy satellite BeppoSAX. Sensitive in the 4-120 keV band, the HPGSPC will study all astrophysical sources emitting in the poorly studied hard X–ray band. The design and performances of the instrument are reported together with results of the on...

Optical materials for near infrared Wollaston prisms

The optical characteristics of birefringent materials transmitting in the near IR (0.9-2.5 μm) are analyzed. Wollaston prisms with large beam separation and virtually free from lateral chromatism – e.g. with fields of view arcmin and image elongation – could be manufactured using  or  (YLF). These materials are used for non linear applications and may therefore find another...

Identification of a complete sample of northern ROSAT All-Sky Survey X-ray sources - II. The optical observations

We describe a program for the optical identi fication of a re presen tative sample of RASS sources contained in six study areas north of , with including one region near the North Galactic pole (NGP) and one near the North Ecliptic pole (NEP) and present some pre liminary results. A full identi fication has been carried out for a count-rate and area-limited complete sub sample...

Surveys of ultraviolet-excess quasar candidates in large fields - The area around NGC 450

We describe the results of a survey for moderately bright quasars performed in a 20.6-square-degree field around the galaxy NGC 450. The quasar candidates were selected on the basis of their ultraviolet excess: by comparative visual inspection of the double image of each single object on a U/B dual-exposure Schmidt photographic plate, 95 primary and 45 secondary quasar candidates...

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 .