Showing papers in "Astrophysical Journal Supplement Series in 1986"

The Palomar-Green Catalog of Ultraviolet-Excess Stellar Objects

Abstract: On presente le catalogue qui donne les positions avec une precision de 8'', les magnitudes photographiques B a 0,29 mag pres, les types spectraux, des references et les couleurs de Stromgren. Parmi les 1874 objets du catalogue, 1715 constituent un echantillon statistiquement complet couvrant 10714 degres carres de 266 champs du Palomar

Damped Lyman-Alpha Absorption by Disk Galaxies with Large Redshifts. I. The Lick Survey

Abstract: On presente les spectres basse resolution (Δλ=10 A) de 68 QSO de grand deplacement vers le rouge. L'un des buts principaux de l'etude est de presenter une liste de raies d'absorption qui soient des candidats pour les «disques Ly α»

Comprehensive models of diffuse interstellar clouds : physical conditions and molecular abundances

Abstract: The limitations of steady state models of interstellar clouds are explored by means of comparison with observational data corresponding to clouds in front of Zeta Per, Zeta Oph, Chi Oph, and Omicron Per. The improved cloud models were constructed to reproduce the observed H and H2(J) column densities for several lines of sight. The main difference from previous models is the treatment of self-shielding in the H2 lines. Other improvements over previous models are discussed as well.

The chemical composition of carbon stars. I. Carbon, nitrogen, and oxygen in 30 cool carbon stars in the Galactic disk

Abstract: The chemical compositions of 30 Galactic carbon stars are determined from high-resolution infrared (1.5-2.5 ¡im) spectra and new model atmospheres. Elemental C, N, and O abundances (with respect to hydrogen) are obtained from lines of the C2 Phillips system’s Ay = -2 sequence, the CN red system’s Ay = -2 sequence, and the CO X '2 vibration-rotation second-overtone bands. The C/C ratios are extracted from the CN Ay = —2 sequence and, in two semi-independent ways, from the CO firstand second-overtone bands. Metal abundances are determined from a handful of atomic fines. Spectra at 3-4 jüim for a few stars provide additional fines which are used as checks. These include the HCN 3 fim bands, the CN red system’s Af = 3 sequence, and the NH X 2 and the CH X U fundamental vibration-rotation bands. The H2 1-0 S(0) fine near 2.22 ^m is also available as a check. Model atmospheres accounting for the fine blanketing by the poly atomics HCN and C2H2 were computed for a grid of effective temperatures and surface gravities. Selected models for differing opacities and assumptions (e.g., surface heating) were computed. Effective temperatures are on the scale established by lunar occultation angular diameters. The surface gravity is based on a mean stellar mass and absolute luminosity. The principal results are as follows: 1. The dispersion in C, N, and O abundances for the 30 program stars is small. 2. The stars show only modest carbon enrichments; the most carbon-rich star has C/O -1.6, and about 50% of the stars in the sample have C/O <1.1. 3. The C abundance is, in general, low, with 30

Diffusion coefficients for stellar plasmas

Abstract: On presente une methode approximee de calcul des coefficients de diffusion pour des plasmas denses caracteristiques des enveloppes de naines blanches

The Binary Frequency and Origin of the OB Runaway Stars

Abstract: A radial velocity survey of the bright northern OB runaway stars has been undertaken to determine the frequency of binary stars in this high-velocity group. A total of 634 high-dispersion spectrograms of 36 proposed runaway stars were obtained over a two year period. Approximately half of the stars are velocity-variable; these include seven spectroscopic binaries, one possible beta-Cephei variable, and 10 stars with emission lines in their spectra. The latter group contains seven of the eight Be stars observed and three luminous O stars, and it is argued that their variability is caused by nonradial pulsation. Fifteen of the program stars have a peculiar radial velocity greater than 30 km/s; five others are probable runaways on the basis of distance from the galactic plane and proper motion. Only two of the confirmed and probable runaways, HD 3950 and HD 198846 (Y Cyg), are binaries, and both are double-lines systems. New orbital elements are presented for HD 3950 and the five new binary systems found among the low-velocity stars. The statisical methods used to assess velocity variability and periodic signals are described in detail. The higher fractional abundance of runaways among more massive stars, their binary frequency, and the properties ofmore » the runaway binaries suggest that they obtained their high velocities through single-binary, binary-binary, or n-body close encounters during the early dynamical evolution of associations. 208 references.« less

Spectra of Late-Type Standard Stars in the Region 2.0--2.5 Microns

Abstract: Atlas des spectres en bande K de 26 etoiles ayant des abondances proches du soleil, situees dans une classe spectrale de F8 a M7 et etant en luminosite naines a supergeantes

A versatile method for obtaining structures of rapidly rotating stars

Abstract: On formule une nouvelle methode de calcul a deux dimensions pour obtenir les structures d'etoiles en rotation rapide et de disques gazeux

A survey of bimolecular ion-molecule reactions for use in modeling the chemistry of planetary atmospheres, cometary comae, and interstellar clouds

Abstract: This is a supplement to a previous paper (Anicich & Huntress 1986). It is a survey of bimolecular positive ion-molecule reactions with potential importance to the chemistry of planetary atmospheres, cometary comae, and interstellar clouds. This supplement covers the literature from 1986 through 1991, with some additional citations missed in the original survey. Over 200 new citations are included. A table of reactions is listed by reactant ion, and cross-references are provided for both ionic and neutral reactants and also for both ionic and neutral products.

The Structure of Brightest Cluster Members. I. Surface Photometry

Abstract: La photometrie de surface des galaxies elliptiques brillantes dans les cœurs des amas de galaxies, combinee a la photometrie tiree de la litterature, a permis de constituer un echantillon de 261 galaxies elliptiques dans 63 amas dans le domaine des magnitudes −18≤M V ≤−25

A Survey of the Millimeter-Wave Spectrum of Sagittarius B2

Abstract: More than 60 percent of the millimeter wave spectrum between 70 and 150 GHz of the giant Sgr B2 molecular cloud was surveyed with the Bell Laboratories 7 m telescope at a spectral resolution of 1 MHz. The observations and instrumentation are described, including beam efficiency and beamwidth as functions of frequency, frequency coverage, and rms noise. The catalog used to identify the 457 lines found is summarized, and the analysis of the data to determine column densities and rotational temperatures is discussed. The range of rotational temperatures obtained and their relation to the kinetic temperature, and their implications for the hydrogen density, are considered. More than 300 lines are transitions of 21 molecules, and the results for these are analyzed, giving excitation diagrams for most of them. A partly successful attempt is made to use ratios of the calculated abundances to predict abundances of as yet undetected species. Finally, the spectra for the entire survey are presented.

Diffusion in white dwarfs - New results and comparative study

Abstract: On presente de nouvelles estimations des echelles de temps de diffusion des elements lourds dans les naines blanches

Theory of Axisymmetric Magnetohydrodynamic Flows: Disks

Abstract: On propose une theorie generale pour les ecoulements magnetohydrodynamiques ideaux, a symetrie axiale, stationnaires, relativistes, autour d'un trou noir ou d'une etoile magnetisee en rotation

The Structure and Dynamics of Ringed Galaxies. I. The Morphology of Galaxy Rings, and Statistics of Their Apparent Shapes, Relative Sizes, and Apparent Orientations with Respect to Bars

Abstract: On a mesure les diametres apparents, les rapports des axes et les angles donnant les positions relatives de la barre et du disque de 1200 objets

The rotational emission-line spectrum of orion a between 247 and 263 ghz

Abstract: Results are presented from a molecular line survey of the core of the Orion molecular cloud between 247 and 263 GHz. The spectrum contains a total of 243 resolvable lines from 23 different chemical species. When combined with the earlier survey of Orion from 215 to 247 GHz by Sutton et al. (1985), the complete data set includes over 780 emission features from 29 distinct molecules. Of the 23 molecules detected in this survey, only NO, CCH, and HCO^+ were not identified in the lower frequency data. As a result of the supporting laboratory spectroscopy performed to supplement existing millimeter-wave spectral line catalogs, only 33 of the more than 780 lines remain unidentified, of which 16 occur in the upper frequency band. A significant chance remains that a number of these unidentified lines are due to transitions between states of either isotopically substituted or highly excited abundant and complex molecules such as CH_3OH, CH_3OCH_3, and HCOOCH_3, whose rotational spectra are poorly known at present. The very small percentage and weak strength of the unidentified lines implies that the dominant chemical constituents visible at millimeter wavelengths have been identified in the Orion molecular cloud.

Population studies. II: Kinematics as a function of abundance and galactocentric position for [Fe/H]≤−0.6

Abstract: On presente un catalogue de quelques 1200 objets galactiques dont les vitesses radiales et les abondances [Fe/H]≤−0,6 sont connues. On a analyse ces donnees pour en deduire des informations concernant les proprietes cinematiques des populations les plus vieilles de la Galaxie et l'interdependance de la cinematique et des abondances

A survey of chromospherically active stars

Abstract: Photometric and/or spectroscopic observations have been obtained of 52 late-type stars which are suspected or known to be chromospherically active. Although not all types of observations were obtained for each star, these observations include all-sky BVRI Johnson photometry, ultraviolet spectrograms, low-dispersion blue-wavelength spectrograms, and high-dispersion red-wavelength spectrograms. From the spectroscopic observations v sin i's, radial velocities, and the appearance of the Ca II H and K emission lines have been determined as well as the H-alpha line. The photometric observations indicate that chromospherically active stars have V - R and V - I color excesses. Such excesses will affect the surface fluxes determined with the surface brightness-color relationship. On the other hand all-sky BVRI photometry appears to be an excellent way to identify chromospherically active stars. A small group of moderately rapidly rotating, possibly single G8-K2 giants has been found. These stars have very modest chromospheric activity and so are not FK comae stars. A number of other unusual chromospherically active stars are identified.

A Catalog of Markarian Galaxies

Abstract: A catalog of Markarian galaxies is presented which tabulates redshifts, spectral and morphological classifications, magnitudes, infrared and radio flux densities, and over 600 references to available data published before January 1, 1986. Redshifts are now available for 1228 objects with strong ultraviolet continua, and follow-up spectroscopic and photometric observations of Markarian galaxies have provided classifications of 115 Seyfert 1, 43 Seyfert 2, and 137 starburst and H II-type galaxies. After a description of the Markarian survey and the current catalog, a summary of the general results obtained from the data is presented. A preliminary study of the infrared properties of Markarian galaxies as measured by IRAS reveals a number of interesting results, including the existence of a sample of elliptical and lenticular galaxies with appreciable infrared emission. 450 references.

Optical manifestations of mass outflows from young stars - At atlas of CCD images of Herbig-Haro objects

Abstract: An attempt is made to provide deep CCD images suitable for tracing the shock-excited and scattered-light components characterizing extended Herbig-Haro complexes. Tabular data include astrometric positions for all stars, shock-excited emission knots, prominent scattered-light patches, as well as an identification for all H-alpha emission objects within the CCD images. It is concluded that: (1) optical outflows are not always accompanied by molecular flows, (2) optical outflows show a higher degree of collimation than their molecular counterparts, and (3) the Herbig-Haro phenomenon is not restricted to low-mass young stellar objects.

A versatile method for obtaining structures of rapidly rotating stars. II: Three-dimensional self-consistent field method

Abstract: Formulation d'une nouvelle methode permettant d'obtenir les structures d'une etoile en rotation rapide et de systemes multiples, y compris binaires

Protostellar formation in rotating interstellar clouds. V - Nonisothermal collapse and fragmentation

Abstract: Numerical calculations are presented for rigorous models spanning a four-dimensional parameter space of initial conditions of the three-dimensional collapse of rotating protostellar clouds, encompassing radiative transfer in the Eddington approximation and detailed thermodynamical relations. It is found that protostellar formation may involve a few stages of hierarchical fragmentation terminated by increased thermal pressure in the nonisothermal regime, that high thermal energy clouds remain nearly axisymmetric during the first dynamic collapse phase, and that very slowly rotating clouds can fragment. The presolar nebula was probably formed from a cloud with very little initial rotation.

The MIT-Green Bank (MG) 5 GHz survey

Abstract: The catalog yielded by the MIT-Green Bank 5-GHz survey contains 5974 sources with S/N ratio greater than 5; a supplemental catalog contains 3836 possible detections with S/N of less than 5. The reliability of the main list is measured to be about 96 percent, with a completeness of about 95 percent. Flux density errors are a function of flux density. A comparison is presently made of survey sources from the Douglas et al. (1980) 365-MHz Texas survey; spectral indices are computed for coincident sources, and the distribution of spectral indices is discussed.

E. W. Fick Observatory stellar radial velocity measurements. I - 1976-1984

Abstract: Table d'environ 16 000 observations de vitesses radiales stellaires enregistrees debut 1976

Narrow absorption components and variability in ultraviolet P Cygni profiles of early-type stars

Abstract: Etude des spectres UV de 21 etoiles de la sequence principale, geantes et supergeantes, de type B1-O4

Transformation Equations and Other Aids for VRI Photometry

Abstract: On decrit deux nouvelles techniques basees sur les travaux de Gutierrez-Moreno, permettant de tenir compte des effets du saut de Paschen

Theoretical UVBY beta Indices

Abstract: On presente les indices photometriques theoriques dans des systemes de Stromgren et β pour les grilles de Kurucz publiees ou non. Ces indices ont ete places dans des systemes standards en utilisant des distributions d'energie UV et visuelles des standards pgotometriques secondaires