%R 1999A&AS..135....1E %J-3 %A Eyer L., Bartholdi P. %T Variable stars: Which Nyquist frequency? %M ds1574 %F 1999.01.29 %B In the analysis of variable stars, the problem of sampling is central. This article focusses on the determination of the Nyquist frequency. It is well defined in the case of regular sampling. However, the time series of variable stars observations are generally unevenly sampled. Fourier analysis using the spectral window furnishes some clues about the equivalent Nyquist frequency in the irregular case. Often it is pushed very high, and thus very short periods can be detected. A specific example is shown, drawn from MACHO databases. %K stars: variable - methods: analytical - methods: data analysis %R 1999A&AS..135....5C %J-28 %A Chereul E., Creze M., Bienayme O. %T The distribution of nearby stars in phase space mapped by Hipparcos. III. Clustering and streaming among A-F type stars. %M ds1599 %F 1999.01.29 %B This paper presents the detailed results obtained in the search of density-velocity inhomogeneities in a volume limited and absolute magnitude limited sample of A-F type dwarfs within 125 parsecs of the Sun. A 3-D wavelet analysis is used to extract inhomogeneities, both in the density and velocity distributions. Thus, a real picture of the phase space is produced. Not only are some clusters and streams detected, but the fraction of clumped stars can be measured. By estimating individual stellar ages one can relate the streams and clusters to the state of the interstellar medium (ISM) at star formation time and provide a quantitative view of cluster evaporation and stream mixing. Having established this picture without assumption we come back to previously known observational facts regarding clusters and associations, moving groups or so-called superclusters. In the 3-D position space, well known open clusters (Hyades, Coma Berenices and Ursa Major), associations (parts of the Scorpio-Centaurus association) as well as the Hyades evaporation track are retrieved. Three new probably loose clusters are identified (Bootes, Pegasus 1 and 2). The sample is relatively well mixed in the position space since less than 7 per cent of the stars belong to structures with coherent kinematics, most likely gravitationally bound. The wavelet analysis exhibits strong velocity structuring at typical scales of velocity dispersion <{sigma}>_stream_~6.3, 3.8 and 2.4km/s. The majority of large scale velocity structures (<{sigma}>_stream_~6.3km/s) are Eggen's superclusters (Pleiades SCl, Hyades SCl and Sirius SCl) with the whole Centaurus association. A new supercluster-like structure is found with a mean velocity between the Sun and Sirius SCl velocities. These structures are all characterized by a large age range which reflects the overall sample age distribution. Moreover, a few old streams of ~2Gyr are also extracted at this scale with high U components. We show that all these large velocity dispersion structures represent 63% of the sample. This percentage drops to 46% if we remove the velocity background created by a smooth velocity ellipsoid in each structure. Smaller scales (<{sigma}>_stream_~3.8 and 2.4km/s) reveal that superclusters are always substructured by 2 or more streams which generally exhibit a coherent age distribution. At these scales, background stars are negligible and percentages of stars in streams are 38% and 18% respectively. %K methods: data analysis, Galaxy: solar neighbourhood - galaxies open clusters and associations - galaxies: kinematics and dynamics %R 1999A&AS..135...29H %J-40 %A Hric L., Galis R. %T New periods of variable stars in Cygnus based on a quarter of century of photographic observations. %M ds7599 %F 1999.01.29 %B This work summarizes the results of photographic photometry obtained over 24 years at the Skalnate Pleso (1979-1993) and Asiago (1969-1988) observatories. The period of light changes, the epoch of the maximum or of the minimum, the type of variability and, in some cases, possible causes of the long-term behaviour of light changes were determined for 17 variable stars. %K stars: techniques: photometric - stars: variables: general %R 1999A&AS..135...41D %J-56 %A Delfosse X., Tinney C.G., Forveille T., Epchtein N., Borsenberger J., Fouque P., Kimeswenger S., Tiphene D. %T Searching for very low-mass stars and brown dwarfs with DENIS. %M ds7839 %F 1999.01.29 %B We present the results of infrared spectroscopic observations of a sample of very low-mass stars and brown dwarf candidates detected in a 230 square degree area by the DENIS (DEep Near Infrared Southern sky; Epchtein, 1997Msngr..87...27E) survey. We find that objects as faint as the faintest known stars are easily detected by DENIS. This sample also includes three members of the new ``L'' dwarf class, one of which was the first confirmed isolated field brown dwarf. As this data represents ~1% of the total DENIS survey area, the completed survey can be expected to have a dramatic impact on the study of the faintest stars and brown dwarfs. In particular, it should detect ~300 of the new and poorly understood ``L'' class of dwarfs. %K stars: low-mass,brown dwarfs - stars: luminosity function, mass function - infrared: stars - surveys %R 1999A&AS..135...57H %J-63 %A Handler G., Paunzen E. %T A search for rapid oscillations in chemically peculiar A-type stars. %M ds1619 %F 1999.01.29 %B In 1995 we initiated a Northern Hemisphere survey for rapidly oscillating Ap stars. This paper presents the results including one new roAp star (HD 122970), the confirmation of rapid oscillations of HD 99563 and apparent null results for other stars. Using Hipparcos data a statistical analysis of the absolute magnitudes and galactic distributions of all known roAp and noAp stars (also taken from the literature) was made. A systematic trend for most of the program stars in a M_V_ vs. {beta} (index of the Stroemgren uvby{beta} system) diagram was detected leading to the conclusion that {beta} is systematically influenced by the chemical peculiarity and/or magnetic field. Three roAp stars are outside the {delta} Scuti instability strip which implies that the driving mechanism of the two classes of pulsating star is different. This is also suggested by new pulsation models. No statistical difference between the galactic distribution of roAp and noAp stars was found. %K stars: chemically peculiar - stars: oscillations %R 1999A&AS..135...65F %J-73 %A Fornasier S., Lazzarin M., Barbieri C., Barucci M.A. %T Spectroscopic comparison of aqueous altered asteroids with CM2 carbonaceous chondrite meteorites. %M ds7952 %F 1999.01.29 %B In the last year we have started a spectroscopic investigation of asteroids located in the region of the main-belt between about 2.2 and 3.6AU. The aim of this work is to study the aqueous alteration process which acted in that zone, dominated by low albedo C-type asteroids, and to compare the spectra of these hydrous objects with those of CM2 carbonaceous chondrite meteorites. In fact, the spectra of these meteorites reveal features probably due to aqueous altered materials on their surfaces. The study of the aqueous alteration process can give important information on the chemical and thermal evolution of the earliest Solar System. More that 65% of the investigated objects have revealed features suggesting the presence of hydrous materials. The comparison of the spectra of the hydrated asteroids obtained to date with those of several CM2 carbonaceous chondrite meteorites seems to indicate that aqueous altered asteroids could be the parents of CM2 meteorites. The data have been obtained during several observational runs at the Asiago Observatory with the 1.8m telescope and at ESO-LaSilla with the 1.5m telescope. %K meteors, meteoroids - minor planets, asteroids - solar systems: formation %R 1999A&AS..135...75T %J-82 %A Taylor B.J. %T A zero point and accidental errors for published values of [Fe/H] for cool giants. %M ds8000 %F 1999.01.29 %B This paper is one of a series based on published values of [Fe/H] for late-type evolved stars. Only values of [Fe/H] from high-dispersion spectroscopy or related techniques are used. The narrative in this paper begins at a point where mean values of [Fe/H] have been derived for {epsilon} Vir, {alpha} Boo, {beta} Gem, and the Hyades giants. By using these stars as standard stars when necessary, a zero-point data base is assembled. This data base is then expanded into its final version by correcting and adding additional data in a step-by-step process. As that process proceeds, data comparisons are used to establish rms errors. Derived rms errors per datum are found to be about 0.10-0.12dex, and they appear to be too large to be explained by line-to-line scatter and temperature effects. %K methods: statistical - stars: abundances %R 1999A&AS..135...83M %J-101 %A Marquez I., Durret F., Petitjean P. %T Near infrared observations of quasars with extended ionized envelopes. %M ds1608 %F 1999.01.29 %B We have observed a sample of 15 and 8 quasars with redshifts between 0.11 and 0.87 (mean value 0.38) in the J and K' bands respectively. Eleven of the quasars were previously known to be associated with extended emission line regions. After deconvolution of the image, substraction of the PSF when possible, and identification of companions with the help of HST archive images when available, extensions are seen for at least eleven quasars. However, average profiles are different from that of the PSF in only four objects, for which a good fit is obtained with an r^1/4^ law, suggesting that the underlying galaxies are ellipticals. Redshifts were available in the literature for surrounding objects in five quasar fields. For these objects, one to five companion galaxies were found. One quasar even belongs to a richness class 1 cluster. Most other quasars in our sample have nearby galaxies in projection which may also be companions. Environmental effects are therefore probably important to account for the properties of these objects. %K galaxies: active - galaxies: fundamental parameters - galaxies: interactions - galaxies: photometry - quasars: general - infrared: galaxies %R 1999A&AS..135..103A %J-109 %A Alcaino G., Liller W., Alvarado F., Kravtsov V., Ipatov A., Samus N., Smirnov O. %T Bright populations of the LMC cluster NGC 1978 from multicolor CCD photometry. %M ds7575 %F 1999.01.29 %B We have carried out multicolor (BVRI) photometry for 3077 stars in the field of the populous cluster NGC 1978 in the Large Magellanic Cloud. We find a clear discrepancy in the zero point of our V magnitudes in NGC 1978 with earlier work (Bomans et al. 1995A&A...298..427B). A large sample of horizontal-branch stars (319 objects) has been isolated. Our study of color distributions of HB stars in different parts of the cluster reveals some variations of the shape of the distributions across the cluster face. We also find some difference in CMD positions of the lower giant branch dependent upon the position in the cluster. Thus, we do not exclude the presence of two subpopulations in NGC 1978; to explain the observations, a difference in [Fe/H] by ~0.1-0.2 between them would be sufficient. %K galaxies: star clusters - Magellanic Clouds - clusters: globular: individual: \object{NGC 1978} (LMC) - HR diagram %R 1999A&AS..135..111S %J-131 %A Souchay J., Loysel B., Kinoshita H., Folgueira M. %T Corrections and new developments in rigid earth nutation theory. III. Final tables ``REN-2000" including crossed-nutation and spin-orbit coupling effects. %M ds7187 %F 1999.01.29 %B We present here the new tables REN-2000 of the nutation for a rigid Earth model, starting from Hamiltonian theory, with a level of truncature at 0.1 {mu}as for individual coefficients instead of 5{mu}as Kinoshita & Souchay (1990, Celest. Mech. 48, 187). For this presentation to be achieved we first carry out the calculations of the second-order effects due to crossed-nutations and spin-orbit coupling, at the same level of truncation as above. This paper is the third and last one in the frame of the complete reconstruction of the theory of the rigid Earth nutation. It is the complementary part to previous studies concerning the luni-solar nutation involving indirect planetary effects Souchay & Kinoshita (1996A&A...312.1017S) and the influence of the second-order geopotential (J_3_, J_4_) and of the direct planetary effect Souchay & Kinoshita (1997A&A...318..639S). Quasi-diurnal and sub-diurnal nutations coming from the harmonics of degree 2, 3 and 4 of the geopotential are also included in REN-2000, their values being taken from Folgueira et al. (1998, Celest. Mech. 69, 373). A presentation of the series REN-2000 is done at the end of the paper, with separated informations for each contribution. %K reference systems - earth %R 1999A&AS..135..133V %J-144 %A Vauglin I., Paturel G., Borsenberger J., Fouque P., Epchtein N., Kimeswenger S., Tiphene D., Lanoix P., Courtois H. %T First DENIS I-band extragalactic catalog. %M ds8041 %F 1999.01.29 %B This paper presents the first I-band photometric catalog of the brightest galaxies extracted from the Deep Near Infrared Survey of the Southern Sky (DENIS) An automatic galaxy recognition program has been developed to build this provisional catalog. The method is based on a discriminating analysis. The most discriminant parameter to separate galaxies from stars is proved to be the peak intensity of an object divided by its array. Its efficiency is better than 99%. The nominal accuracy for galaxy coordinates calculated with the Guide Star Catalog is about 6 arcsec. The cross-identification with galaxies available in the Lyon-Meudon Extragalactic DAtabase (LEDA) allows a calibraton of the I-band photometry with the sample of Mathewson et Al. Thus, the catalog contains total I-band magnitude, isophotal diameter, axis ratio, position angle and a rough estimate of the morphological type code for 20260 galaxies. The internal completeness of this catalog reaches magnitude I_lim_=14.5, with a photometric accuracy of ~0.18 m. 25% of the Southern sky has been processed in this study. This quick look analysis allows us to start a radio and spectrographic follow-up long before the end of the survey. %K galaxies: general - catalogs - galaxies: photometry - surveys %R 1999A&AS..135..145R %J-158 %A Rozas M., Zurita A., Heller C.H., Beckman J.E. %T Global properties of the population of HII regions in NGC 7479 from photometric H{alpha} imaging. %M ds8075 %F 1999.01.29 %B We present a new high quality continuum-subtracted H{alpha} image of NGC 7479. Using a novel semi-automated technique we have determined the positions, angular sizes, and absolute fluxes of over 1000 HII regions and have constructed the luminosity function for the regions over the whole galaxy, showing that its slope is within the published range for spirals of the same morphological type. However NGC 7479 is notable in that its bar shows unusually strong star formation along the whole structure. This prompted us to undertake separate analyses of the HII regions in the bar and in the disc. The disc luminosity function (LF) shows clean bi-linear behaviour as found previously in late-type spirals, with a break at log L_H{alpha}_=38.6erg/s, whereas the bar LF shows a much less regular form. The difference is not due to the small numbers of HII regions in the bar, but reflects a physical difference between the bar and the disc in the properties of their sets of regions. We show separate plots of the parameters for HII regions in the bar and the disc selected for their regular shapes and absence of blending. We have derived galaxy-wide relations for the HII region set: the diameter distribution function, luminosity versus volume and number versus luminosity versus diameter, and deduced the global H{alpha} surface density distribution and disc scale length. Measuring the integrated diffuse H{alpha} flux for the galaxy, we compare this with the computed ionizing flux escaping from the population of density-bounded HII regions, finding that both in terms of energy balance and of geometry, the hypothesis that this escaping flux gives rise to the diffuse H{alpha} is well borne out in NGC 7479, and that a significant fraction of this flux escapes completely into the intergalactic medium. %K galaxies: individual (NGC 7479) - galaxies: spiral - galaxies: ISM %R 1999A&AS..135..159M %J-169 %A Mendoza C., Zeippen C.J., Storey P.J. %T Atomic data from the IRON Project. XXXIII. Radiative rates for the intercombination transitions in the carbon isoelectronic sequence. %M ds1589 %F 1999.01.29 %B Radiative decay rates are computed with the atomic structure code superstructure for the 2s2p^3^ ^5^S^o^_2_ - 2s^2^2p^2^ ^3^P_1_, ^3^P_2_ and ^1^D_2_ intercombination transitions of the carbon isoelectronic sequence (6 <=Z <=28). Contributions from configuration interaction and relativistic corrections are carefully studied, in particular the spin-spin interaction that is shown to be of considerable importance for low Z. By extensive comparisons with other theoretical datasets and measurements of the ^5^S^o^_2_ radiative lifetime and the B=A(^5^S^o^_2_ - ^3^P_2_)/A(^5^S^o^_2_ - ^3^P_1_) branching ratio, we are able to assign accuracy ratings to the present transition probabilities. The transitions to the ground term are believed to be accurate to better than 10% whereas the smaller A-values belonging to transitions to the ^1^D_2_ are not expected to be accurate to more than 20%. %K atomic data %R 1999A&AS..135..171L %J-185 %A Landi E., Del Zanna G., Breeveld E.R., Landini M., Bromage B.J.I., Pike C.D. %T Relative intensity calibration of CDS-GIS detectors on SOHO using a plasma diagnostic technique. %M ds7869 %F 1999.01.29 %B The internal intensity calibration of the Coronal Diagnostic Spectrometer (CDS) - Grazing Incidence Spectrometer (GIS) is studied using the Arcetri diagnostic method. A large number of spectral lines observed by the four GIS detectors in solar active and quiet regions is analysed in order to determine the relative intensity calibration curve of the instrument. The plasma diagnostic method developed in Arcetri allows the measurement of the correction factors to the pre-flight CDS - GIS internal intensity calibration curves and of the relative calibration between different detectors. No gross deviations from the pre-flight calibration are found. Also the GIS 3 and GIS 4 second order sensitivites are measured. The problems of fixed patterning, ghosting, anomalous line profiles and widths are also discussed, and a list of lines suitable for further diagnostic studies with GIS is presented. %K space vehicles: instruments - techniques: miscellaneous %R 1999A&AS..135..187B %J-195 %A Bendinelli O., Bonaccini D., Falsini S., Parmeggiani G. %T A method to analyze adaptive optics images of binary stars. %M ds7343 %F 1999.01.29 %B We present a fast and robust ad-hoc method to analyze a set of short exposure images of a close binary star taken by the adaptive optics system of the ESO 3.6 m telescope. At first each image is fitted, assuming as a radially symmetrical approximation of its ``instantaneous'' PSF, the superposition of a central Gaussian and of a Moffat torus. Owing to the coral variability and asymmetry of the PSF the fit gives a poor estimate of the component's luminosity ratio; nevertheless it reproduces satisfactorily the global structure of the PSF and above all gives the accurate sub-pixel positions of the two stars. This allows to obtain, by the shift-and-add procedure, the mean set image from which the final parameters of the two stars and the mean PSF during the observing run are derived. The results from a set of AO images of the close binary system {tau} Canis Maioris are consistent with those previously obtained by one of us using the iterative blind deconvolution. Extensive simulations give evidence that the magnitude difference and the separation of the components can be estimated within about 0.05mag and 0.005" respectively when the secondary star image does not overlap a bright artifact of the AO system. %K stars: individual: {tau} Canis Majoris - instrumentation - adaptive optics; techniques: image processing %R 1999A&AS..135..197T %J-197 %A Trevese D., Cirimele G., Cenci A., Appodia B., Flin P., Hickson P. %T (Erratum) Properties of nearby clusters of galaxies. III. A 76, A 157, A 407, A 505, A 671, A 779, A 1700, A 2028, A 2040, A 2052, A 2063, A 2065, A 2593, A 2657, A 2670. %M ds1293 %F 1999.01.29 %B Erratum to Astron. Astrophys. Suppl. Ser. 125, 459-469 (1997). %R 1999A&AS..135..197G %J-197 %A Georgiev L., Borissova J., Rosado M., Kurtev R., Ivanov G., Koenigsberger G. %T (Erratum) The Local Group dwarf irregular galaxy IC 1613. I. The young stellar content. %M ds7636 %F 1999.01.29 %B Erratum to Astron. Astrophys. Suppl. Ser. 134, 21-37 (1999)