%R 1997A&AS..126....1G %J-2 %A Gili R., Couteau P. %T Mesures d'etoiles doubles faites aux lunettes de 74 et 50 cm de l'Observatoire de la Cote d'Azur. Measurements of double stars made at Nice Observatory with the 74 and 50 cm refractors. %M ds1319 %F 1997.11.04 %B We give 657 measurements of double stars, Table 1 by R. Gili with CCD camera, Table 2 by P. Couteau with filar micrometer. %K binaries: visual - astrometry %R 1997A&AS..126....3H %J-13 %A Horellou C., Booth R. %T CO and HI in a southern sample of interacting galaxies. I. The data. %M ds1338 %F 1997.11.04 %B Using SEST, the Parkes antenna and the Australia Telescope Compact Array, we have made a survey of the ^12^CO(1-0) and HI emission of an optically-selected sample of =~60 southern interacting and merging galaxies. In this paper we present the data and determine global masses of neutral gas (in molecular and atomic form) for the observed galaxies. We have detected HI in 26 systems and found that these galaxies have less than 15% of their gas in molecular form. %K galaxies: interaction - galaxies: ISM - galaxies - evolution - radio lines: galaxies %R 1997A&AS..126...15S %J-19 %A Simien F., Prugniel P. %T Kinematical data on early-type galaxies. II. %M ds1307 %F 1997.11.04 %B We present new kinematical data for a sample of 38 early-type galaxies. Rotation curves and velocity-dispersion profiles are determined for 32 objects, while the central velocity dispersions are given for the whole sample. This is our second 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...21N %J-30 %A Nordstroem B., Stefanik R.P., Latham D.W., Andersen J. %T Radial velocities, rotations, and duplicity of a sample of early F-type dwarfs. %M ds5793 %F 1997.11.04 %B We present new radial and rotational velocities for 595 nearby early F dwarfs, based on digital spectra cross-correlated with individually optimised synthetic template spectra. The selection of optimum templates, the determination of rotational velocities, and the extraction of velocities from the blended spectra of double-lined spectroscopic binaries are discussed in some detail. We find 170 spectroscopic binaries in the sample and determine orbits for 18 double-lined and 2 single-lined binaries, including some spectroscopic triples. 73 stars are listed with too rapid rotation to yield useful radial velocities (i.e. vsini>120km/s). We discuss the binary frequency in the sample, and the influence of unrecognised binaries on the definition of clean metallicity groups of young F dwarfs and the determination of their kinematical properties. %K methods: statistical - techniques: radial velocities - stars: binaries: spectroscopic - stars: kinematics - Galaxy: solar neighbourhood %R 1997A&AS..126...31H %J-37 %A Hirte S., Schilbach E., Scholz R.-D. %T The Potsdam contribution to the extragalactic link of the Hipparcos proper motion system. %M ds6075 %F 1997.11.04 %B Absolute proper motions of 360 Hipparcos stars in 24 fields well distributed over the northern sky were derived from measurements of photographic plates taken mainly with the Tautenburg Schmidt telescope (134/200/400cm). In each field (about 10 square degrees) a large number of galaxies was used to link the proper motions to the extragalactic reference system. Because of systematic magnitude-dependent errors, which affect the proper motion determination of bright stars, only the 256 stars with B>=9.0 were used to determine the spin parameters of the Hipparcos system. The accuracy of the final result is 0.5mas/yr for all three spin parameters. %K astrometry - methods: statistical - reference systems - catalogs - stars: kinematics %R 1997A&AS..126...39S %J-65 %A Steffen M., Szczerba R., Men'shchikov A., Schoenberner D. %T Hydrodynamical models and synthetic spectra of circumstellar dust shells around AGB stars. I. Stationary solutions. %M ds1324 %F 1997.11.04 %B We present a sample of hydrodynamical steady state models of circumstellar gas/dust shells around late type giants together with computed spectral energy distributions (SEDs). In these models, the stellar wind is driven by radiation pressure on dust grains and subsequent momentum transfer to the gas molecules via collisions. Given the fundamental stellar parameters (M_*_, L_*_, T_eff_), the mass loss rate ({dot}(M)), and the dust properties, a self-consistent physical model of the circumstellar gas/dust shell is obtained from the numerical solution of the coupled equations of hydrodynamics and radiative transfer. The computed outflow velocities and infrared fluxes of the circumstellar envelopes can be compared directly with the observed properties of stars on asymptotic giant branch. Plotting the positions of our steady state models in different IRAS two-color-diagrams, we confirm that, for fixed dust properties, all models fall on a simple color-color relation with {dot}(M) (or optical depth) as the only parameter. Surprisingly, we find a good agreement between the synthetic spectra resulting from the self-consistent hydrodynamical approach and those obtained from much simpler models based on a constant outflow velocity and ignoring drift of dust relative to the gas. Our models are compared with the results of similar calculations by Netzer & Elitzur (1993ApJ...410..701N). We find significant differences which are probably the result of some unrealistic approximations in the treatment of radiative transfer underlying the model calculations of Netzer & Elitzur. Moreover, our results demonstrate that, in general, gas pressure cannot be neglected for winds with relatively low expansion velocities (u_e_<30km/s). For given stellar parameters and dust properties, the theoretical minimum (maximum) mass loss rate decreases (increases) significantly when gas pressure is taken into account. %K stars: AGB and post-AGB - circumstellar matter - stars: mass loss - dust, extinction - hydrodynamics - radiative transfer %R 1997A&AS..126...67A %J-72 %A Andreon S., Davoust E., Poulain P. %T Morphological classification and structural parameters of galaxies in the Coma and Perseus clusters. %M ds1308 %F 1997.11.04 %B We present the results of an isophotal shape analysis of galaxies in the Coma and Perseus clusters. These data, together with those of two previous papers, provide two complete samples of galaxies with reliable Hubble types in rich clusters: 1) all galaxies brighter than m_b_=16.5 falling within one degree (=2.3Mpc) from the center of the Coma cluster (187 galaxies), 2) all galaxies brighter than m_Zwicky_=15.7 in a region of 5{deg}3'x5{deg}27' around the center of the Perseus cluster (139 galaxies). These two complete samples cover 5 orders of magnitude in galaxy density and span areas of 91 and 17Mpc^2^, clustercentric radii up to 6.4 and 2.3Mpc, for Perseus and Coma respectively. They will be used in subsequent papers to study the dependence of galaxy types on cluster environment and as reference samples in comparisons with distant clusters. %K galaxies: clusters: individual: Coma (\object{Abell 1656}) - individual: Perseus (\object{Abell 426}) - Galaxies: elliptical and lenticular, cD - galaxies: fundamental parameters %R 1997A&AS..126...73L %J-80 %A Lahulla J.F., Aguirre A., Hilton J. %T (BVRI) photometric sequences for nine selected dark globules. %M ds1320 %F 1997.11.04 %B Using a CCD detector, BVRI photometry has been carried out in the vicinity of nine Lynds dark nebulae. In conjunction with spectroscopic data which could be obtained at a later stage, the data listed herein could be used for possible distance determinations of the nine nebulae. %K galaxies: general - ISM: clouds - ISM: dust, extinction %R 1997A&AS..126...81F %J-90 %A Foster D.C., Byrne P.B., Hawley S.L., Rolleston W.R.J. %T CCD photometry of late-type stars in the young open cluster IC 2602. %M ds5607 %F 1997.11.04 %B We present the results of VRI photometry of the young open cluster IC 2602. Two 15 arcmin x 15 arcmin fields were observed in February and May 1991 using the 1-m Swope telescope at Las Campanas. Using theoretical isochrones obtained from D'Antona & Mazzitelli (1994ApJS...90..467D), and allowing for observational and other uncertainties, we identify 78 primary candidate members with 12=50%, as might be expected given its low galactic latitude. We also compare our photometry with that given for the X-ray detected stars of Randich et al. (1995A&A...300..134R). We present complimentary narrow band H{alpha} photometry for a subset of the stars. %K stars: evolution - stars: late-type - open clusters: individual: IC 2602 %R 1997A&AS..126...91T %J-103 %A Teodorani M., Errico L., Vittone A.A., Giovannelli F., Rossi C. %T Spectroscopic and photometric behaviour of the FU Orionis variable Z Canis Majoris. %M ds1261 %F 1997.11.04 %B We present optical and IR photometry, optical multi-dispersion spectroscopy, and IR spectrophotometry of the FU Ori variable Z Canis Majoris, obtained in the years 1984, 1985, 1989 and 1996. A comparison of data obtained in 1984 and 1985 confirms that in 1985 Z CMa underwent a low-power eruption. The enhancement of H{alpha} emission line, the transition of H{beta} and Feii lines from pure absorption to emission with or without a P Cygni profile, the appearance of the Hei 6678{AA} absorption line, a radial velocity increase of about 30% of the P Cygni absorption components, and finally a 0.2-0.3mag increase of IR luminosity, were all dinstinctive characteristics of this state. Further observations in 1996 show that Z CMa is in a low-luminosity state at V=10.24 while the appearance of a double-peaked H{alpha} emission, with the blue component much weaker than the red one, is the most significant spectroscopic variation. Energy distributions in the range 0.4-5{mu}m, obtained during 1984 and 1985 observational runs, are also presented. %K stars: individual: Z CMa - stars: pre-main-sequence - stars: Be - stars: variables: other %R 1997A&AS..126..105B %J-111 %A Berrington K.A., Tully J.A. %T Atomic data from the IRON Project. XXIV. Electron excitation of Li-like Fe XXIV between the n = 2 and n' = 2, 3, 4 fine-structure levels. %M ds1346 %F 1997.11.04 %B 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 n<=4. Autoionizing resonances are found to affect 18 of the 39 collision strengths, namely those for transitions 2lj -n'l'j' where n' = 2, 3. The present calculation is carried out only for electrons incident on the ground state with energies not exceeding 265 Ry. Beyond this we use the relativistic distorted wave collision strengths of Zhang et al. in order to complete our results. Thermally averaged collision strengths are computed and tabulated as functions of logT for transitions out of the 2s_1/2_, 2p_1/2_ and 2p_3/2_ states. The temperature range considered is 6.2<=logT<=8.0, Fe XXIV having its maximum coronal abundance when logT=7.2. %K Li-like iron - electron collision - atomic data %R 1997A&AS..126..113S %J-119 %A Sen A.K., Kakati M. %T Instrumental polarization caused by telescope optics during wide field imaging. %M ds1313 %F 1997.11.04 %B When astronomical observations are made for a celestial object, with non -zero field angle (wrt telescope axis), the beam of parallel rays from the celestial object strikes the telescope mirror obliquely. Each unpolarized ray of light when it strikes the metal coated mirror surface gets polarized due to reflection. On the contrary, when the field angle is zero, these reflected rays for a field star, combine together to produce an instrumental polarization effect. A 100% linearly polarized star when observed even at zero field angle, exhibits depolarization due to the above effect. A detailed procedure has been worked out here to estimate such polarization effects at the prime and Cassegrain focii, considering the case for linear polarizations only. Also to find the typical values of such polarization, a 2.3m telescope having beam sizes f/3.23 and f/13 at the prime and Cassegrain focii, has been considered. The instrumental polarization values as calculated at these two focii are 0.000092 and 0.016104% at the field angles 300 and 90 arcsec, respectively. Furthermore, a 100% polarized star when observed at the above two focii will appear to be 99.9999 and 99.9983% polarized respectively due to depolarization. %K techniques: polarimetric techniques - telescopes - polarization %R 1997A&AS..126..121V %J-149 %A von Hoensbroech A., Xilouris K.M. %T Effelsberg multifrequency pulsar polarimetry. %M h0278 %F 1997.11.04 %B A sample of 64 well-calibrated pulsar polarization profiles measured at cm-wavelengths with the Effelsberg radio telescope is presented. All profiles were measured using an adding and a multiplying polarimeter which enables polarimetry over wide-bandwidths. Gain imbalances introduced by the active components in the signal path, as well as system imperfections, alter the polarization state of the incoming radiation. An analysis of the signal path of those devices is presented, together with a dynamic calibration procedure introduced to eliminate the instrumental errors. The results were used to trace the location of the radiating region in pulsar magnetospheres at high frequencies. %K polarization - techniques: polarimetric - pulsars: general - pulsars: individual: PSR B0136+57, PSR B0301+19, PSR B0329+54, PSR B0355+54, PSR B0450+55, PSR B0525+21, PSR B0540+23, PSR B0740-28, PSR B0809+74, PSR B0823+26, PSR B0919+06, PSR B0950+08, PSR B1133+16, PSR B1237+25, PSR B1642-03, PSR B1822-09, PSR B1915+13, PSR B1929+10, PSR B1946+35, PSR B2016+28, PSR B2020+28, PSR B2021+51, PSR B2045-16, PSR B2154+40, PSR B2310+42, PSR B2319+60, PSR B2351+61 %R 1997A&AS..126..151G %J-160 %A Gaertner S., Benoit A., Lamarre J.-M., Giard M., Bret J.-L., Chabaud J.-P., Desert F.-X., Faure J.-P., Jegoudez G., Lande J., Leblanc J., Lepeltier J.-P., Narbonne J., Piat M., Pons R., Serra G., Simiand G. %T A new readout system for bolometers with improved low frequency stability. %M ds1334 %F 1997.11.04 %B A new readout electronic system for bolometers is presented in this paper. The bolometer resistance is measured in a bridge with a capacitive load, using a periodic square wave bias current. The bias voltages at both ends of the bridge are balanced in order to keep the middle point around zero. Only changes around this zero value are amplified and detected synchronously with the bias signal. These features shift the measurement frequency out of the electrical low frequency noises (JFETs), and reduces the dynamics required from the amplification chain. The bias voltages are fully controlled by computer, and the lock-in detection is digital. This readout electronic has many advantages over previous ones. In particular, it proved to be able to read the total power of the radiation reaching the bolometer, and to perform measurements down to low frequencies (<=0.1Hz) without significant additional noise. These features open new observation strategies such as full sky scanning to bolometer instruments on board future submillimetre space projects having high thermal background levels (warm telescope). The different steps of the development of this new readout electronics on the ground-based Diabolo experiment are described, the performances reached are discussed, and a version suitable for the readout of the arrays of bolometers on the COBRAS/SAMBA satellite mission is presented. %K instrumentation: detectors; instrumentation: photometer - methods: data analysis - methods: numerical %R 1997A&AS..126..161W %J-167 %A Weber R., Faye C., Biraud F., Dansou J. %T Spectral detector for interference time blanking using quantized correlator. %M ds1327 %F 1997.11.04 %B Given the large flow of data to be processed, quantized correlators are widely used in radio astronomy. Unfortunately, the occurrence of non-Gaussian interference combined with a coarse quantization can strongly alter the shape of the estimated spectra. The final spectral estimation can be preserved by blanking the correlator in real-time. A new interference detection criterion is proposed within this framework. It uses the real-time capabilities of correlators and compares contaminated and non-contaminated correlation functions. No a priori information on the interfering signals is required. Simulations, using synthetic and actual data, are presented. This new technique of real time detection can significantly improve the quality of spectral line observations. %K instrumentation: miscellaneous - methods: data analysis - techniques: spectroscopic %R 1997A&AS..126..169M %J-176 %A Martin V.A.F., Leister N.V. %T Absolute declinations from astrolabe data. %M ds5743 %F 1997.11.04 %B We show the results of an evaluation of a global reduction method for Danjon astrolabe observations. The approach is much simpler but more precise than the conventional method. The new form of the equations gives us the possibility of using the entire set of an observational programme using the data from different catalogues taken at two zenith distances (30{deg} and 45{deg}). The observational programme contains about 15000 observations of 381 different stars taken at the ``Observatorio Abrahao de Moraes" (OAM, {phi} = 23{deg}00'06"S; {lambda} = 03^h^07^m^52.2^s^W), Valinhos, Sao Paulo, Brazil. The reduction was based on the FK5 system. We discuss the possibility to compute absolute declinations through the stars belonging simultaneously to the 30{deg} and 45{deg} zenith distance programmes. The absolute declination corrections were determined for 269 stars with a precision of 0.13", and the value of the determined equator correction is 0.028"+/-0.034". The instrumental effects were also determined. %K astrometry - astrolabe - reference system - fundamental stars and other objects %R 1997A&AS..126..177K %J-181 %A Krishnakumar V., Venkatakrishnan P. %T Determination of the atmospheric point spread function by a parameter search. %M ds5557 %F 1997.11.04 %B The result of blind deconvolution is a reconstructed image that has non positive intensities. The number of these non positive pixels has been used as an estimator for the departure from a perfect reconstruction. Simulations of reconstruction of objects convolved with a kernel having one or two parameters are shown to demonstrate the efficiency of the estimator. We thus present a technique of determining the unknown parameters of the point spread function by searching for the point in parameter space with the lowest number of nonpositive pixels. It is also shown that the parameters of the convolving kernel can be obtained even in the presence of noise. This method was validated using a long exposure image of NGC 1409. %K techniques: image processing - atmospheric effects - globular clusters: individual: NGC 1409 %R 1997A&AS..126..183F %J-195 %A Fulle M., Colangeli L., Mennella V., Rotundi A., Bussoletti E. %T Simulation of the dust flux on the ROSETTA probe during the orbiting phase around comet 46P/Wirtanen. %M ds5781 %F 1997.11.04 %B We present a probabilistic model of the dust mass, flux and fluence which will be collected by the ROSETTA probe while orbiting around comet 46P/Wirtanen. The dust environment of the target comet is simulated according to the most recent data available in the literature. Best fits of the DIDSY-GIOTTO data collected during the fly-by of comet 1P/Halley have shown that the probabilistic properties of dust ejection from the inner coma are crucial Fulle et al. 1995A&A...304..622F). Therefore, we pay particular attention to the dust ejection velocity, which is assumed to have a wide distribution around the most probable values, and the dust ejection distribution, which is assumed to have a strong anisotropy peaked towards the sun. To compute the impact velocity in the probe reference frame, the rigorous keplerian orbit of each grain is considered taking into account aberrations due to the probe orbital velocity. We analyse the dependence of the results on the probe orbit parameters, such as true anomaly, probe-nucleus distance, orbit node and inclination. Computations are performed for the six main directions of the probe reference frame and for different values of the acceptance angle. The only way to collect direct grains is to point towards the nucleus; the mass collected in this direction is almost independent of the acceptance angle and of the time evolution of dust loss rate. A strong dependence of the collected dust mass on node and inclination is evidenced. By assuming an acceptance angle of 40{deg}, the flux of reflected grains received in the two directions perpendicular to the probe orbit is higher than that in the nucleus direction, for 42% of randomly oriented probe orbits. The value increases up to 56% when the acceptance angle in the directions perpendicular to the probe orbit is increased up to 80{deg}. The dust ejection anisotropy produces a strong dependence of the fluxes on the probe anomaly. For reflected grains, the fluences show relevant depletions at the largest masses, due to dust orbital effects, and the collected masses strongly depend on the acceptance angle and on the time evolution of the dust loss rate. The total dust fluxes are evaluated by assuming a half sphere field of view (corresponding to an acceptance angle of 180{deg}). %K Comets: general - Comets: individual: \objnS{46P/Wirtanen}