%R 1997A&AS..126..385P
%J-391
%A Patriarchi P., Perinotto M.
%T Wind variability in central stars of planetary nebulae. II.
%M h0114
%F 1997.12.03
%B New high resolution IUE spectra of central stars of the planetary nebulae (CSPN) NGC 40, NGC 6543, NGC 6826, and BD +30 3639 have been obtained between August 1994 and September 1995 to explore the variability of their P Cygni profiles. The data have been analyzed together with previous observations of the same stars. Significant changes in the profiles of several of the typical wind lines of the N V, O IV, O V, Si IV, C IV, and N IV ions have been revealed in all the observed
stars. By combining these results with the ones obtained in a previous paper of this series (Patriarchi & Perinotto 1995A&AS..110..353P; Paper I), it is found that half of the fourteen observed CSPN exhibit changes in the shape of their P Cygni profiles up to levels of 10-50% in timescales of years, analogous to similar timescale variations exhibited by hot stars of population I. They are: NGC 40, NGC 1535, NGC 2392, NGC 6543, NGC 6826, IC 4593 and BD +30 3639. The ones for which changes have
not been detected are: NGC 246, NGC 6210, NGC 6572, NGC 7009, IC 418, IC 2149 and Lo 8. The present paper completes the survey of this type (at least 2-3 well separated high resolution good exposures for each star) that could have been done in central stars of planetary nebulae using the IUE satellite. In a typical case (NGC 1535) we estimate that the changes in the physical properties of the wind, resulting from the observed changes in the P Cygni profiles, amount for
{dot}(M)q_NV_ to a factor of 3+/-1.
%K planetary nebulae: general - stars: mass loss

%R 1997A&AS..126..393O
%J-400
%A Ostensen R., Remy M., Lindblad P.O., Refsdal S., Stabell R., Surdej J., Barthel P.D., Emanuelsen P.I., Festin L., Gosset E., Hainaut O., Hakala P., Hjelm M., Hjorth J., Hutsemekers D., Jablonski M., Kaas A.A., Kristen H., Larsson S., Magain P., Pettersson B., Pospieszalska-Surdej A., Smette A., Teuber J., Thomsen B., Van Drom E.
%T ESO & NOT photometric monitoring of the Cloverleaf quasar.
%M ds5908
%F 1997.12.03
%B The Cloverleaf quasar, H1413+117, has been photometrically monitored at ESO (La Silla, Chile) and with the NOT (La Palma, Spain) during the period 1987-1994. All good quality CCD frames have been successfully analysed using two independent methods (i.e. an automatic image decomposition technique and an interactive CLEAN algorithm). The photometric results from the two methods are found to be very similar, and they show that the four lensed QSO images vary significantly in
brightness (by up to 0.45mag), nearly in parallel. The lightcurve of the D component presents some slight departures from the general trend which are very likely caused by micro-lensing effects. Upper limits, at the 99% confidence level, of 150 days on the absolute value for the time delays between the photometric lightcurves of this quadruply imaged variable QSO, are derived. This is unfortunately too large to constrain the lens model but there is little doubt that a better
sampling of the lightcurves should allow to accurately derive these time delays. Pending a direct detection of the lensing galaxy (position and redshift), this system thus constitutes another good candidate for a direct and independent determination of the Hubble parameter.
%K gravitational lensing - techniques: image processing - quasars: H1413+117 (\object{QSO 1413+117})

%R 1997A&AS..126..401M
%J-406
%A Magnier E.A., Augusteijn T., Prins S., van Paradijs J., Lewin W.H.G.
%T Cepheids as tracers of star formation in M 31. I. Observations and identifications.
%M dst6720
%F 1997.12.03
%B Cepheid variables can be used for more than just a distance indicator. Since the age can be determined from the period, they can be used to trace the star formation history of a galaxy. We have identified 130 new Cepheid variable candidates in M 31, particularly along the spiral arm regions in the north-east of the galaxy. These areas had not been searched for Cepheids in the previous study by Baade and collaborators. The contamination of our sample by other types of
variables is low (<3%). For V<21, the completeness is =~53%. These Cepheids will be used to explore the star formation history in M 31.
%K (stars: variables:) Cepheids - stars: formation - galaxies: individual: M 31 - galaxies: stellar content - (cosmology:) distance scale

%R 1997A&AS..126..407P
%J-411
%A Paunzen E., Gray R.O.
%T A spectroscopic survey for {lambda}Bootis stars. I. Strategy, techniques and first results.
%M ds5970
%F 1997.12.03
%B In recent years, the chemically peculiar (CP) stars of the upper main sequence have become a fruitful field for the testing of astrophysical theories. Processes such as diffusion, convection and mass loss have been developed theoretically and introduced into models. The group of {lambda} Bootis stars, however, is remarkable among the chemically peculiar stars as they are nonmagnetic, PopulationI, A to F-type dwarfs which show significant underabundances of metals (except
for C, N, O and S). Unfortunately, the small number of confirmed members of the {lambda} Bootis class makes a sound statistical analysis of their properties impossible. Thus, it is still difficult to decide between the two theories - mass loss with diffusion and the accretion theory - which have been proposed to explain the origin of these stars.
We therefore have started a spectroscopic survey to find new {lambda} Bootis stars in the field as well as in open clusters and associations. The presence of {lambda} Bootis stars in open clusters and associations would permit a determination of the ages of these stars, and thus would yield an important test for distinguishing between the two theories. In this paper we describe the selection of candidates using photometric criteria, the basic requirements, spectroscopic
follow-up observations and results from the first three observing runs. Special care was taken to avoid misclassification of our programme stars (e.g. {lambda} Bootis stars are often confused with intermediate PopulationII, He-weak or high vsini stars), using a refined MK system. The discovery of at least six new {lambda} Bootis stars (including three in the Orion OB1 association) shows the efficacy of our selection criteria.
%K surveys - stars - {lambda} Bootis - stars: chemically peculiar - stars: early type; stars: fundamental parameters

%R 1997A&AS..126..413R
%J-435
%A Reich P., Reich W., Fuerst E.
%T The Effelsberg 21 cm radio continuum survey of the Galactic plane between l = 95.5deg and l = 240{deg}.
%M ds1364
%F 1997.12.03
%B We present the results of a radio continuum survey at 21 cm wavelength of the Galactic plane between 95.5deg<=l<=240{deg} and -4{deg}<=b<=+5{deg} with the Effelsberg 100-m telescope. The data have been absolutely calibrated by using the Stockert northern sky survey at the same wavelength. This survey complements the Effelsberg 21 cm Galactic plane survey for l<=95.5deg by Reich et al. (1990A&AS...83..539R). The results are presented as contour maps with a sensitivity of 
100mK T_B_ at an angular resolution (HPBW) of 9.4.' In addition we extend the list of compact sources given by Reich et al. (1990A&AS...83..539R) by 1830 new entries. These sources have peak flux densities exceeding 160mK T_B_ (or 79mJy/beam area) and apparent sizes of less than 16'.
%K catalogs - surveys - galactic: general

%R 1997A&AS..126..437H
%J-469
%A Hirth G.A., Mundt R., Solf J.
%T Spatial and kinematic properties of the forbidden emission line region of T Tauri stars.
%M ds1318
%F 1997.12.03
%B We have carried out a long-slit spectroscopic survey for 38 T Tauri stars (TTSs) to study the spatial and kinematic properties of their forbidden emission line (FEL) regions. With these observations we hope to provide more insight into the complex physical structure of the outflows from young stars on the smallest spatial scales observable by long-slit spectroscopy. Due to the differential nature of the observational method, information on the spatial properties (offset
from the stellar continuum and spatial width) on sub-arcsec (sub-seeing) scales can be obtained. For most TTSs the [OI] {lambda}{lambda}6300, 6363, [NII] {lambda}6583 and [SII] {lambda}{lambda}6716, 6731 lines have been investigated at a typical spatial resolution of 1.5'' and a velocity resolution of 20-50km/s. A sub-sample of 9 closeby stars (Haro 6-10, XZ Tau, UZ Tau E, HN Tau, DO Tau, DP Tau, UY Aur, RW Aur and V536 Aql) has been extensively studied and the
direction of their outflows has been approximately determined by taking spectra at several slit position angles, if not known from emission-line CCD imaging. The spatial and kinematic properties of the FEL regions of these 9 TTSs are described in detail. Together with 3 additional stars discussed in the literature, a sample of 12 stars provides the basis for the following main results of our survey: The so-called high-velocity component (HVC) of the FELs (or gas of high
velocity which presumably represents in many cases a HVC being blended with emission of lower velocity) is generally spatially more extended than the so-called low-velocity component (LVC, or gas near the stellar velocity). In the [SII] {lambda}6731 line the centroid of the high-velocity gas is located typically at distances of 0.6'' from the TTS while for the low-velocity gas this value is smaller on average by more than a factor of 3. Comparing the spatial properties of the
high-velocity gas among the investigated FELs, it turns out that the largest spatial width and the largest offset of the centroid from the star is usually observed in the [NII] {lambda}6583 line, while the emission region is most compact in the [OI] {lambda}6300 line. In [OI] the centroid of the high-velocity gas is typically offset by only 0.2'' from the star whereas in [SII] and [NII] 3 and 3.5 times larger average values have been measured, respectively. In the case of the
low-velocity gas, the smallest offset of the emission centroid is also observed in [OI] (typically 0.1'' in [OI] and 0.2'' in [SII]). Our data provide additional support for the model of Kwan & Tademaru (1988, 1995) according to which the HVC observed in the FELs of many TTSs is formed in a well-collimated jet, while the LVC represents gas from a physically distinct flow component (possibly a disk wind or a disk corona). The larger spatial extent of the high-velocity gas
in [SII] and [NII] compared to that in [OI] is most probably the result of a jet decreasing in density with increasing distance from the source combined with an increase in excitation. The decrease of the electron density with distance is rather obvious for a jet with diverging stream lines, but why the electron temperature increases is unclear.
%K stars: pre-main-sequence - stars: variable - stars: emission-line - ISM: jets and outflows

%R 1997A&AS..126..471T
%J-478
%A Tamazian V.S., Theureau G., Coudreau-Durand N.
%T 21-cm line observations of galaxies from Kazarian's lists.
%M ds1348
%F 1997.12.03
%B The 21-cm neutral hydrogen line has been measured for the first time in 39 non-Seyfert type galaxies from Kazarian list, with the Nancay radiotelescope. The line profiles, widths at 20% and 50% of the peak intensity, radial velocities as well as total fluxes are presented. The values of radial velocity are in fairly good agreement with those obtained from optical spectra. The width values at 20% of the peak vary in wide range from 113km/s (KAZ 579) to 608km/s for
KAZ 566. Nine of our objects remained undetected, whether their HI-flux was too faint, the integration time too short, or the frequency sighted wrong. However, for part of them, there were positive hint of detection. Comments on individual objects are given.
%K galaxies: general - radio lines: galaxies

%R 1997A&AS..126..479G
%J-502
%A Garcia-Lario P., Manchado A., Pych W., Pottasch S.R.
%T Near infrared photometry of IRAS sources with colours like planetary nebulae. III.
%M ds1259
%F 1997.12.03
%B We present the near infrared photometry of a new sample of 225 IRAS sources, many of them previously unidentified in the literature, selected because their far infrared colours are similar to those shown by known planetary nebulae. The results obtained are used to establish the main source of near infrared emission. Combining this information with the far infrared IRAS data and a few additional criteria we determine the nature and evolutionary stage of all the sources
observed so far, including those for which near infrared photometry was previously reported in Papers I and II. Among the unidentified IRAS sources in our sample we find only a small percentage of planetary nebulae, many of them very young and dusty, showing peculiar near infrared colours. Most of the new objects observed in the near infrared are identified as transition objects in the previous stages of the stellar evolution. Among them, we find heavily obscured late-AGB
stars, early post-AGB stars still obscured by thick circumstellar envelopes which are probably the true progenitors of planetary nebulae, and a significant fraction of stars with bright optical counterparts showing little or no near infrared excess, which we associate with highly evolved post-AGB stars with low mass progenitors, which may never become planetary nebulae. In addition, we also find a small percentage of young stellar objects, as well as a few Seyfert galaxies.
We conclude that, in most cases, based on near infrared data alone, it is not possible to give a confident classification of the unidentified IRAS source. However, the near infrared is shown to be a powerful tool, specially when dealing with objects which are heavily obscured in the optical. In this case, the detection of the near infrared counterpart is the only way in which we can extend the study of these sources to other spectral ranges and may be crucial to understand
the short-lived phase which precedes the formation of a new planetary nebula.
%K stars: AGB and Post-AGB - infrared: general - planetary nebulae: general

%R 1997A&AS..126..503M
%J-508
%A Ma J., Peng Q.-H., Chen R., Ji Z.-H., Tu C.-P.
%T Scaleheights of 486 southern spiral galaxies and some statistical correlation.
%M ds6045
%F 1997.12.03
%B Based on Peng's method (1988A&A...206...18P), we obtain scaleheights of 486 southern spiral galaxies, the images of which are taken from the Digitized Sky Survey at Xinglong Station of Beijing Astronomical Observatory. The fitted spiral arms of 70 galaxies are compared with their images to get their optimum inclinations. The scaleheights of other 416 ones are listed in Table A1 in Appendix. After compiling and analyzing the data, we find some statistical correlations. The most
interesting results are that a flatter galaxy is bluer and looks brighter, and galaxies become flatter along the Hubble sequence Sab - Scd.
%K galaxies: fundamental parameters - galaxies: spiral - galaxies: structure

%R 1997A&AS..126..509M
%J-517
%A Molthagen K., Wendker H.J., Briel U.G.
%T Multiwavelength observations of the field HS 47.5/22 in Ursa Major. I. The X-ray catalogue of a medium deep ROSAT survey.
%M ds1369
%F 1997.12.03
%B 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 contains 574 X-ray sources. The identifications are mainly based on the HQS objective prism plate
which allows object classification down to a magnitude m_b_<~18.5mag , and a rough distinction between red and blue objects more than a magnitude deeper. Follow-up observations were performed for a number of objects, mainly faint quasar candidates.
%K methods: data analysis - catalogues - surveys - X-rays: general - X-rays: galaxies

%R 1997A&AS..126..519S
%J-523
%A Simien F., Prugniel P.
%T Kinematical data on early-type galaxies. III.
%M ds1373
%F 1997.12.03
%B We present new kinematical data for a sample of 24 early-type galaxies. Rotation curves and velocity-dispersion profiles are determined for 21 objects, while the central velocity dispersions are given for the whole sample. This is our third paper in a series devoted to the presentation of kinematical data on elliptical and S0 galaxies, derived from long-slit absorption spectroscopy.
%K galaxies: elliptical & lenticular, cD - galaxies: kinematics and dynamics - galaxies: fundamental parameters

%R 1997A&AS..126..525P
%J-535
%A Piro L., Matt G., Ricci R.
%T Soft excesses of hard X-ray selected Seyfert 1 galaxies studied with the ROSAT-PSPC.
%M ds6063
%F 1997.12.03
%B The nature of the soft X-ray excess in Seyfert 1 galaxies is still an open issue. In order to derive some general properties we analysed the ROSAT PSPC archive observations of the Seyfert galaxies in the Nandra & Pounds (1994MNRAS.268..405N) Ginga sample. The use of this sample ensures a reliable estimate (under the assumption of lack of intrinsic spectral variability) of the slope of the underlying power law, which instead cannot be well measured using ROSAT data alone. We tested
three different models for the soft excess: emission from accretion disk (described by a black body), absorption from ionized gas (``warm absorber'', described by an absorption edge), and reflection from mildly ionized material (described by a step function). The main result is that no model gives a satisfactory fit for all sources. Furthermore for two sources none of these models provides an acceptable fit. In these cases a physically meaningful combination of two components
(e.g. warm absorber plus black body) gives a good fit. We conclude that several different effects concur to the soft excess phenomenon in Seyfert galaxies.
%K galaxies: Seyfert; X-rays: galaxies

%R 1997A&AS..126..537B
%J-546
%A Bravo-Alfaro H., Szomoru A., Cayatte V., Balkowski C., Sancisi R.
%T The HI distribution of spiral galaxies in the cluster A 262.
%M ds5853
%F 1997.12.03
%B We present results of an HI survey of the cluster of galaxies Abell 262, using the Westerbork Synthesis Radio Telescope (WSRT). Eleven galaxies were detected in five fields. In a few cases the gas in these galaxies shows an asymmetrical distribution; the most likely explanation is the interaction between the cluster medium and the gaseous disks. Only two of the detected galaxies are slightly HI-deficient. At 40" to the West of CGCG 160-049 we tentatively detect what may
be an associated HI cloud. The total mass of this cloud is 2.5x10^8^M_{sun}_, and no optical counterpart has yet been found.
%K galaxies: clusters: individual: Abell 262 - radio lines: galaxies

%R 1997A&AS..126..547B
%J-553
%A Buffa F., Porceddu I.
%T Temperature forecast and dome seeing minimization. I. A case study using a neural network model.
%M ds6059
%F 1997.12.03
%B Dome seeing may strongly deteriorate the final sharpness of a point source astronomical image, reducing its Image Quality. Both the telescope enclosure and the mirrors may contribute to the dome seeing, if air convection is induced by differences of temperature between them and external air. The prediction of the external air temperature with respect to a given time interval allows one to preset in advance the air conditioning temperature value in the telescope enclosure.
With the aim to study the neural networks capabilities and limits to make short term temperature prediction, a few case studies have been carried out by using an autoregressive neural network model. The actual goal is to understand if and with which constraints a neural network model can actually be used in a NTT-like dome (i.e. telescope is in open air when observing and heat sources are highly controlled when close or inside the telescope's dome) for steering the daytime
air conditioning system. We do not present any interface with an actual telescope: this paper presents a feasibility study about the forecasting methodological approach rather than its operational application to a specific telescope. The results show that on site output prediction of a neural network are competitive with respect to a linear prediction approach.
%K turbulence - methods: data analysis - methods: statistical - site testing

%R 1997A&AS..126..555A
%J-561
%A Aristidi E., Carbillet M., Prieur J.-L., Lopez B., Bresson Y., Koechlin L.
%T ICCD speckle observations of binary stars: Measurements during 1994-1995.
%M ds6321
%F 1997.12.03
%B We present speckle observations of nineteen double stars and the triple star 2 Cam. Angular separations, absolute position angles and relative photometry result from these observations. The angular separation is derived from the power spectrum. The position angle and the relative photometry are determined by two recent techniques: the cross-correlation between the speckle images and their square, and the ratios of twofold probability density functions of the images.
%K methods: data analysis - techniques: image processing - techniques: interferometric - binaries: close

%R 1997A&AS..126..563B
%J-571
%A Ballester P., Rosa M.R.
%T Modeling echelle spectrographs.
%M ds6150
%F 1997.12.03
%B A generic description of spectrographs based on first optical principles is developed. It incorporates off-plane grating equations and rotations in three dimensions in order to adequately account for line tilt and order curvature. This formalism is validated by confronting the models for two actual spectrographs (UVES and CASPEC) with ray tracing results and arc lamp exposures. The versatility of these models for the control of instrument configurations, for the generation
of calibration databases, and for the preparation of observations is shown. As an important application, we derive from this formulation various forms of the echelle relation which can be used to implement automatic wavelength calibration procedures. Finally, we discuss possible applications of such analytical models of astronomical instruments for calibration, data analysis and observatory operations.
%K instrumentation: spectrographs - methods: data analysis - techniques: image processing; spectroscopic