%R 1997A&AS..123....1C
%J-4
%A Clement R., Garcia M., Reglero V., Clausen J.V., Bravo A., Suso J., Fabregat J., Torrejon J.M., Reig P., Marco A.
%T Four colour photometry of late-type binary systems. I. First uvby{beta} light curves of ZZ Ursae Majoris.
%M ds1239
%F 1997.05.15
%B This paper presents first complete uvby light curves of the late-type detached eclipsing binary ZZ UMa (G0V + G8V, P=2.2993d). This binary system has been observed during eight campaigns at the Calar Alto Observatory (Almeria, Spain) and at the Sierra Nevada Observatory (Granada, Spain). 294 points distributed over the binary period and covering both eclipses are given. The comparison stars used to calculate the differential light curves (SAO 15242 and SAO 15251) were
confirmed as being good reference stars with constant flux. These observations are part of a 6 year uvby and H{beta} monitoring program of low mass eclipsing binaries whose main objective is to provide accurate absolute astrophysical parameters for late-type main sequence stars. Details about the standardisation process and accuracy of the photometry are also given. The internal accuracy of the standard photometry measured as the mean RMS of the differences between standard
and observed values for the standard stars observed along the program is only a few millimagnitudes. Detailed analysis of ZZ UMa, based on these light curves, will be published separately.
%K stars: binaries: eclipsing - stars: late-type - stars: individual: ZZ UMa - stars: fundamental parameters

%R 1997A&AS..123....5C
%J-20
%A Carquillat J.M., Jaschek C., Jaschek M., Ginestet N.
%T An Atlas of the infrared spectral region. II. The late-type stars (G - M).
%M ds1243
%F 1997.05.15
%B This Atlas illustrates the behavior of late type stars (F, G, K and M) in the near infrared 8400-8800{AA} region with a resolution of about 2{AA}. Seventeen figures illustrate the spectral sequence and luminosity classes V, III, Ib and Ia. Four figures illustrate peculiar spectra, namely those of Am stars, composites, weak metal stars and S and C type objects. The complete Atlas is also available as FITS files from the CDS de Strasbourg and other data centers.
%K atlases - stars: fundamental parameters - stars late type - infrared: stars

%R 1997A&AS..123...21L
%J-23
%A Lu P.Z., Xu T.Q.
%T Optical positions and proper motions of radio stars.
%M ds1266
%F 1997.05.15
%B The optical positions of 31 radio stars were obtained with the 40cm astrograph at Zo-Se 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.
%K astrometry - radio continuum: stars - reference systems

%R 1997A&AS..123...25R
%J-30
%A Rojo Arellano E., Pena J.H., Gonzalez D.
%T Photoelectric uvby-{beta} photometry of the open cluster NGC 2422.
%M ds4808
%F 1997.05.15
%B New and previously observed uvby-{beta} photometry has been utilized to determine membership in the cluster. Reddening and age of the cluster has been determined.
%K open clusters: individual: NGC 2422 - stars: uvby - stars: distances

%R 1997A&AS..123...31R
%J-41
%A Reynoso E.M., Dubner G.M.
%T Cold neutral gas associated with the Gum nebula.
%M ds1235
%F 1997.05.15
%B Based on HI maps covering the 3600 square degrees area delimited by 230{deg}<=l<=290{deg}, -30{deg}<=b<=30{deg}, 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, roughly centered at l=~262{deg}, b=~-3{deg}, is located at ~500pc
and has a radius of ~150pc. We propose that this HI disk is the neutral gas component of the optical nebula, hence becoming the first time in which a structure with the dimensions of the optical nebula is detected in other wavelengths. We analyze the fitting of observations with different theoretical models and conclude that the most plausible interpretation is that the Gum nebula is a supershell produced by the action of repeated SN explosions, where the explosions may
have originated in the aged association Vela OB2. In this context, the thick HI shell shown by Dubner et al. (1992) near (266{deg}, -2.5{deg}) and the Vela SNR are the debris of two of the several outbursts which started in the region about 6x10^6^ years ago. The southern boundary is distorted due to the presence of a ~28{deg} radius shell, which appears to be an interstellar bubble driven by the stellar winds of the O-type star HD 49798.
%K ISM: supernova remnants - ISM: individual objects: Gum nebula - ISM: bubbles - radio lines: ISM

%R 1997A&AS..123...43S
%J-58
%A Schwarz U.J., Goss W.M., Kalberla P.M.W.
%T WSRT HI synthesis absorption study towards Cassiopeia A.
%M ds1233
%F 1997.05.15
%B We present high resolution images of the entire galactic HI spectrum of Cas A and display the whole data cube in various ways; the spatial resolution is 30 arcsec and the velocity resolution is 0.62km/s. In previous studies, observations are described either with lower velocity resolution or with a limited velocity range (below -30km/s), (Bieging et al. 1991ApJS...75..999B; Reynoso et al. 1997A&A...317..203R). Here we concentrate the discussion on the local HI gas, with velocities between -10
and +10km/s. At a velocity of -1.5km/s we find a cold HI feature with a kinetic temperature of typically 25K, with a small region of 1 by 2arcmin with a kinetic temperature below 10K. This feature can be associated with a ^13^CO feature observed by Wilson et al. (1993A&A...280..221W). Based on the new HI absorption results we derive the ratio N_HI_/N(H_2_)=~0.05 .
%K ISM: individual: Cas A ; clouds atoms - radio lines: ISM

%R 1997A&AS..123...59C
%J-61
%A Clement R., Garcia M., Reglero V., Clausen J.V., Bravo A., Suso J., Fabregat J.
%T Four colour photometry of late-type binary systems. II. New light curves of BH Virginis.
%M ds1252
%F 1997.05.15
%B This paper presents new complete uvby light curves of the late-type detached eclipsing binary BH Vir (G0V + G5V, P=0.81687099d).
This binary system has been observed during four campaigns at the Calar Alto Observatory (Almeria, Spain) and at the European Southern Observatory (La Silla, Chile). This observations are part of a 6 year uvby and H{beta} monitoring program of low mass eclipsing binaries which main objective is to provide accurate absolute astrophysical parameters for late-type main sequence stars. 1585 points spreaded over the binary period and covering both eclipses are given. The internal
accuracy of the standard photometry measured as the mean RMS of the differences between standard value and observed value for the standard stars observed along the program is quoted in a few millimagnitudes. Detailed analysis of BH Vir, based on these light curves, will be published separately.
%K stars: binaries: eclipsing - stars: individual: BH Vir

%R 1997A&AS..123...63V
%J-82
%A van den Ancker M.E., The P.S., Feinstein A., Vazquez R.A., de Winter D., Perez M.R.
%T A multiwavelength study of star formation in the very young open cluster NGC 6530.
%M ds1213
%F 1997.05.15
%B The distance and formation history of the very young open cluster NGC 6530 were investigated by studying a total of 132 probable member stars of this open cluster. It was concluded that the distance to NGC 6530 is 1.8+/-0.2kpc, and its interstellar reddening E(B-V) is 0.30mag. Furthermore, we conclude that the extinction law of the intracluster material is normal (i.e. R_V_=3.1), but anomalous extinction laws were found for several more embedded stars in the cluster.
Of the 132 stars included in this study, 11 are suspected to be variable, five show H{alpha} in emission and nine show an infrared excess. Among the member stars of NGC 6530, three were found to be part of the Herbig Ae/Be stellar class, whereas two others are possible members of this stellar group as well. Also, one cluster member is probably a new massive post-AGB star, whereas the same could possibly apply to another member star. Finally, from the distribution of post- and
pre-main sequence stars in the cluster's HR-diagram, it was concluded that the process of star formation in NGC 6530 must have started a few times 10^7^ years ago and, for the less massive stars, is probably still going on today.
%K circumstellar matter - stars: formation - stars: pre-main sequence - dust, extinction - H II regions - open clusters and associations: individual: NGC 6530

%R 1997A&AS..123...83J
%J-92
%A Jordi C., Masana E., Figueras F., Torra J.
%T An analysis of the currently available calibrations in Stroemgren photometry by using open clusters.
%M ds1268
%F 1997.05.15
%B In recent years, several authors have revised the calibrations used to compute physical parameters (M_v_, T_eff_, log g, [Fe/H]) from intrinsic colours in the uvbyH_{beta}_ photometric system. For reddened stars, these intrinsic colours can be computed through the standard relations among colour indices for each of the regions defined by Stroemgren (1966ARA&A...4..433S) on the HR diagram. We present a discussion of the coherence of these calibrations for main-sequence stars. Stars from
open clusters are used to carry out this analysis. Assuming that individual reddening values and distances should be similar for all the members of a given open cluster, systematic differences among the calibrations used in each of the photometric regions might arise when comparing mean reddening values and distances for the members of each region. To classify the stars into Stroemgren's regions we extended the algorithm presented by Figueras et al. (1991A&AS...87..319F) to a wider range of
spectral types and luminosity classes. The observational ZAMS are compared with the theoretical ZAMS from stellar evolutionary models, in the range 6500-30000K. The discrepancies are also discussed.
%K stars: fundamental parameters - open clusters and associations: general - stars: distances - HR diagram - stars: general - techniques: photometric

%R 1997A&AS..123...93P
%J-101
%A Paunzen E., Weiss W.W., Heiter U., North P.
%T A consolidated catalogue of {lambda} Bootis stars.
%M ds5417
%F 1997.05.15
%B {lambda} Bootis stars challenge our understanding of diffusion and accretion processes related to stars and their circumstellar environment, and they are interesting components of the classical instability strip. Attempts to derive group properties with statistical methods are severely limited by the small number of unambiguously identified {lambda} Bootis stars. In general, the subject appears to be obscured by incorrect memberships and it is therefore essential to
provide a sufficiently large catalogue of definitive group members before modeling the {lambda} Bootis phenomenon. This paper describes the first steps towards this goal, based on our current knowledge of well investigated members, leading to a concise definition of {lambda} Bootis stars: PopI hydrogen burning metal poor (except of C,N,O and S) A-type stars. The definition does not depend on phenomenological features, like flux depressions, colour excesses, vsini values,
etc. Based on a new homogeneous catalogue with 45 {lambda} Bootis stars, we discuss classification criteria which can be used for a spectroscopic and photometric all-sky survey for {lambda} Bootis stars in the field and in clusters of different ages.
%K astronomical data bases - catalogues; stars - {lambda} Bootis; stars - chemically peculiar; stars - early type

%R 1997A&AS..123..103Z
%J-114
%A Zickgraf F.-J., Thiering I., Krautter J., Appenzeller I., Kneer R., Voges W.H., Ziegler B., Chavarria C., Serrano A., Mujica R., Pakull M., Heidt J.
%T Identification of a complete sample of northern ROSAT All-Sky Survey X-ray sources. II. The optical observations.
%M ds5657
%F 1997.05.15
%B We describe a program for the optical identification of a representative sample of RASS sources contained in six study areas north of {delta}=-9{deg}, with |b^II^|>20{deg} including one region near the North Galactic pole (NGP) and one near the North Ecliptic pole (NEP) and present some preliminary results. A full identification has been carried out for a count-rate and area-limited complete subsample comprising 674 sources. The ratio of "extragalactic" ( e.g. AGN,
clusters of galaxies) to "stellar" (e.g. coronal emitters, active binaries) counterparts was found to depend on the galactic neutral hydrogen column density, N_H_. In the area near the NGP (low N_H_) "extragalactic" counterparts dominate, while in the area with the highest N_H_ most X-ray sources are identified with stellar counterparts.
%K surveys - X-rays: general - X-rays: galaxies - X-rays: stars - galaxies: active - galaxies: cluster: general

%R 1997A&AS..123..115N
%J-118
%A Ng Y.K., Schultheis M.
%T Field #3 of the Palomar-Groningen Survey. I. Variable stars in the outer edge of the Sagittarius dwarf galaxy.
%M ds5621
%F 1997.05.15
%B A catalogue is presented with variable (RR Lyrae, semiregular and Mira) stars located inside field #3 of the Palomar-Groningen Survey at the outer edge of the Sagittarius dwarf galaxy. One of the semiregular variables is a carbon star, comparable with those found by Azzopardi et al. (1991A&AS...88..265A). Serendipity provides the suggestion, that their carbon stars might not be located inside, but behind the bulge in the Sagittarius dwarf galaxy.
%K stars: carbon; AGB, post AGB; variables: others - local group - galaxies: individual: \objS{Name Sgr dwarf galaxy}{Sagittarius dwarf}

%R 1997A&AS..123..119E
%J-133
%A Einasto M., Tago E., Jaaniste J., Einasto J., Andernach H.
%T The supercluster-void network. I. The supercluster catalogue and large-scale distribution.
%M ds1185
%F 1997.05.15
%B We investigate the distribution of superclusters and voids using a new catalogue of superclusters of rich clusters of galaxies which extends up to a redshift of z=0.12. The new catalogue contains 220 superclusters of rich clusters, of which 90 superclusters have been determined for the first time. Among them there are several very rich superclusters, containing at least eight member clusters. We demonstrate that two thirds of very rich superclusters are concentrated to a
Dominant Supercluster Plane which is situated at a right angle with respect to the plane of the Local Supercluster and adjacent nearby superclusters. We apply several methods to estimate the characteristic distance between superclusters. The results indicate consistently the presence of a quite regular supercluster-void network with scale of =~120h^-1^Mpc. Comparison with random supercluster catalogues shows significant differences between spatial distributions of real and
random superclusters. We determine the selection function of the sample of clusters and suggest that the mean true space density of Abell clusters is 2.6x10^-5^h^3^Mpc^-3^, twice the conventionally used value.
%K cosmology: observations - large-scale structure of the Universe - clusters of galaxies - catalogs

%R 1997A&AS..123..135G
%J-146
%A Ginestet N., Carquillat J.M., Jaschek C., Jaschek M.
%T Spectral classifications in the near infrared of stars with composite spectra. II. Study of a sample of 180 stars.
%M ds5405
%F 1997.05.15
%B A sample of 180 supposedly composite-spectrum stars has been studied on the basis of spectra obtained in the near infrared (8370-8780{AA}) at a dispersion of 33{AA}/mm. The objective was to study the cooler components of the systems. Of our sample, 120 are true composite spectra, 35 are hot spectra of types B, F and 25 are Am stars. We find a strong concentration of the cooler components of the composite spectra around G8III. In view of the difficulty of classifying
composite spectra, because of the superposition of an early type dwarf and a late type giant or supergiant spectrum, we have made several tests to control the classification based upon the infrared region. Since all tests gave positive results, we conclude that our classifications can be considered as being both reliable and homogeneous.
%K stars: classification - infrared: stars - binaries: spectroscopic

%R 1997A&AS..123..147R
%J-158
%A Raassen A.J.J., Uylings P.H.M.
%T Orthogonal operator calculation of E1, M1 and E2 transition probabilities in Ti III and V IV.
%M ds5441
%F 1997.05.15
%B Transition probabilities in the iron group spectra Ti III and V IV are obtained from an accurate description of the 8 lowest even and 4 lowest odd configurations of the atomic system. Results are compared with experiment and current databases.
%K atomic data - Sun: photosphere - stars: abundances

%R 1997A&AS..123..159G
%J-171
%A Galavis M.E., Mendoza C., Zeippen C.J.
%T Atomic data from the IRON Project. XXII. Radiative rates for forbidden transitions within the ground configuration of ions in the carbon and oxygen isoelectronic sequences.
%M ds1285
%F 1997.05.15
%B As part of the IRON Project, radiative rates have been calculated for the forbidden transitions within the ground configuration of atoms and ions in the carbon (2s^2^2p^2^) and oxygen (2s^2^2p^4^) isoelectronic sequences for Z<=28. The atomic structure code superstructure was used, which allows for configuration interaction, relativistic effects and semi-empirical term energy corrections. Comparisons are made with previous theoretical datasets for the same sequences. It is
shown once again that, to obtain reliable transition probabilities, in particular those of the electric quadrupole type, it is essential to use accurate and consistent experimental transition wavelengths. For the C and O sequences such data are fortunately available from the work of Edlen (1983, 1985). The general accuracy of the present probabilities is rated to be within 10%, with the exception of some electric quadrupole transitions in low-Z ions whose radiative rates are
small with an accuracy not better than +/-50%.
%K atomic data - atomic processes

%R 1997A&AS..123..173R
%J-177
%A Rousselet-Perraut K., Vakili F., Mourard D., Morand F., Bonneau D., Stee P.
%T An attempt to detect polarization effects in the envelope of {gamma} Cassiopeiae with the GI2T interferometer.
%M ds1190
%F 1997.05.15
%B We report on the results of an observing run of {gamma} Cassiopeiae using the optical long baseline interferometer Grand Interferometre a 2 Telescopes (GI2T) in the southern France equipped with film-sheet polarizers. Four interferometric baselines ranging from 20 to 40m were obtained on this star during 1994 on September 5th and 6th, with {alpha} Cephei as a calibrator. We aimed at detecting possible variations of the angular diameter of {gamma} Cas as a function of
polarization directions parallel and orthogonal to the north-south baseline of the GI2T. We do not detect any variation of the visibility as a function of Hour Angle on {alpha} Cephei, neither on {gamma} Cas. We find an upper limit of 1.3 on the ratio of the angular diameters of the envelope of {gamma} Cas seen through polarizers parallel and perpendicular to the North-South direction of the GI2T's baseline. We discuss how this limit could constrain density laws in the wind
of this Be star. We clearly resolve {gamma} Cas for increasing baselines in the red continuum whatever the polarization. Assuming the continuum flux originating from a photosphere surrounded by an elliptical gaussian envelope we estimate the extent of the latter as (2.9+/-0.5)mas. This diameter agrees well with the H{alpha} emitting envelope as obtained by other interferometers.
%K circumstellar matter - stars: Be - stars: individual (gamma Cas) - stars: imaging - techniques: interferometric - polarization

%R 1997A&AS..123..179O
%J-182
%A Oliva E., Gennari S., Vanzi L., Caruso A., Ciofini M.
%T Optical materials for near infrared Wollaston prisms.
%M ds1220
%F 1997.05.15
%B The optical characteristics of birefringent materials transmitting in the near IR (0.9-2.5{mu}m) are analyzed. Wollaston prisms with large beam separation and virtually free from lateral chromatism - e.g. with fields of view >1arcmin and image elongation <0.3" - could be manufactured using AgGaS_2_ or LiYF_4_ (YLF). These materials are used for non linear applications and may therefore find another interesting application in IR focal plane instruments. From the optical
point of view the best material is AgGaS_2_ but YLF may be practically more convenient because of its lower refractive index (n~1.45), better thermo-mechanical properties and lower price. New measurements of the transparency of Calcite at room and cryogenic temperatures are also presented, these show significant absorption (=~0.4cm^-1^) of the ordinary ray already at {lambda}=2{mu}m and very strong bands (absorption coefficient a>3cm^-1^) beyond 2.25{mu}m. The absorption
does not decrease significantly when the crystals is cooled, CaCO_3_ should not be therefore used in instruments working beyond 2.0{mu}m.
%K instrumentation: miscellaneous - instrumentation: polarimeters

%R 1997A&AS..123..183L
%J-198
%A Lannes A., Anterrieu E., Marechal P.
%T CLEAN and WIPE.
%M ds1194
%F 1997.05.15
%B Clean is a matching pursuit process which has two weak points: in situations of astrophysical interest, the "clean map" is not stable in the corresponding object representation space, and the "atoms" of this representation (translated versions of the "clean beam") are not well suited for reconstructing the boundaries of the structuring entities of the object at the related resolution level. As a result, Clean must be interrupted before the best possible fit is reached.
How does Wipe wipe Clean clean? First, by introducing a global regularization principle based on the concept of resolution; and second, by conducting the matching pursuit process at the level of the high-resolution basis functions of the object space.
%K methods: data analysis; numerical - techniques: image processing; interferometric