%R=BibCode %A=Authors %B=Abstract %c=Copyright %D=Date of publication %E=Electronic file %F=Original File %I=Institute and/or Footnotes %J-last page %K=Keywords %T=Title %R 1998PASP..110..761F %F ori/PASPv110n749 %J-778 %T CLOUDY 90: Numerical Simulation of Plasmas and Their Spectra. (Invited Review). %A Ferland G.J.,(1) %A Korista K.T.,(1,)(2) %A Verner D.A.,(1) %A Ferguson J.W.,(1,)(3) %A Kingdon J.B.,(1,)(4) %A Verner E.M.(1) %B CLOUDY is a large-scale spectral synthesis code designed to simulate fully physical conditions within an astronomical plasma and then predict the emitted spectrum. Here we describe version 90 (C90) of the code, paying particular attention to changes in the atomic database and numerical methods that have affected predictions since the last publicly available version, C84. The computational methods and uncertainties are outlined together with the direction future development will take. The code is freely available and is widely used in the analysis and interpretation of emission-line spectra. Web access to the Fortran source for CLOUDY, its documentation Hazy, and an independent electronic form of the atomic database is also described. %I (1) Physics Department, University of Kentucky, 177 CP Building, Lexington, KY 40506. %I (2) Current address: Western Michigan University, Department of Physics, Kalamazoo, MI 49008. %I (3) Current address: Physics Department, Box 32, Wichita State University, Wichita, KS 67260-0032. %I (4) Current address: Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218. %R 1998PASP..110..779C %F ori/PASPv110n749 %J-783 %T Accurate Positions for MCG Galaxies. %A Corwin, Harold G. Jr %A Pesenson Igor %A Schmitz Marion %A Kim D.-C. %A Bennett Judy %A Madore Barry F. %A Mazzarella Joseph M. , %A Helou George %I Infrared Processing and Analysis Center, Jet Propulsion Laboratory, M/S 100-22, California Institute of Technology, Pasadena, CA 91125; (hgcjr@ipac.caltech.edu) %B We have measured accurate celestial coordinates for 4741 extragalactic objects, primarily drawn from a list of MCG galaxies with no recently published accurate positions. The standard deviations in the new positions depend slightly on the measurement method but are on the order of 1".0 to 1".2. Standard deviations in the original MCG positions are confirmed to be at the 1'.5-2'.0 level. These new positions were integrated into NED in 1997 December. %K Astrometry %K Galaxies: General %R 1998PASP..110..784H %F ori/PASPv110n749 %J-793 %T Time-resolved Photometry and Spectroscopy of the Cataclysmic Variable V592 Cassiopeiae. %A Huber Mark E. %A Howell Steve B. , %A Ciardi David R. %I Department of Physics and Astronomy, University of Wyoming, Laramie, WY 82071; (mhuber@godzilla.uwyo.edu), (showell@mothra.uwyo.edu), (ciardi@hedora.uwyo.edu) and %A Fried Robert %I Braeside Observatory, P. O. Box 906, Flagstaff, AZ 86002; (captain@braeside.org) %B Over the past 10 years, the cataclysmic variable (CV) V592 Cassiopeiae (LS I 55 -8) has been monitored by one of the authors. We now present time-resolved optical and infrared photometry and optical spectroscopy of this nova-like binary. Analysis of these data provides the first orbital solution for this star. We find an orbital period near 0.114 days (2.7 hr), a system inclination of 28{deg}, and a mass ratio ({\em M}_2_/{\em M}_1_) of 0.19. V592 Cas appears to be a nova-like cataclysmic variable with a massive white dwarf primary and lies inside the CV period gap. %K Stars: Novae, Cataclysmic Variables %K stars: individual (V592 Cassiopeiae) %K stars: individual (\objC{LS I +55 8}{LS I 55 -8}) %R 1998PASP..110..794S %J-803 %T Recalibration of the Wilson-Bappu Effect Using the Singly Ionized Magnesium {\em k} Line. %A Scoville Frederick %A Mena-Werth Jose %I Department of Physics and Physical Sciences, University of Nebraska at Kearney, Kearney, NE 68849-1160; (werth@platte.unk.edu) %B A new calibration of the Wilson-Bappu effect is presented using data from a survey of the singly ionized magnesium (Mg II) {\em h} and {\em k} lines (near 280 nm) taken from the archives of the {\em International Ultraviolet Explorer} satellite. Our sample consisted of 94 stars with absolute magnitudes derived from parallaxes reported from {\em Hipparcos.} We describe the dependencies of the base widths, peak widths, and full widths at half-maximum (FWHM) on the fundamental stellar parameters T_eff_, metallicity, {\rf log}g, and activity. %K Stars: Atmospheres %K Stars: Chromospheres %K Stars: Distances %K Stars: Fundamental Parameters %K Stars: Late-Type %R 1998PASP..110..804Z %F ori/PASPv110n749 %J-809 %T Search for Low-Instability Strip Variables in the Young Open Cluster NGC 2516. %A Zerbi F.M. %A Mantegazza L. %A Campana S., %A Antonello E. %I Osservatorio Astronomico di Brera, Via Bianchi 46, I-23807 Merate, Italy (zerbi@merate.mi.astro.it) %B In this paper we revise and complete the photometric survey of the instability strip of the southern open cluster NGC 2516 published by (ref???)Antonello & Mantegazza. No variable stars with amplitudes larger than 0.02 mag were found. However, by means of an accurate analysis based on a new statistical method, two groups of small-amplitude variables have been disentangled: one with periods of less than 0.25 days (probably {delta} Scuti stars) and one with periods of greater than 0.025 days. The position in the H-R diagram and the apparent timescale may suggest that the stars of the second group belong to a recently discovered new class of variables, named {gamma} Dor variables. They certainly deserve further study. We also present a comparison between the results of the photometric survey and the available pointed {\em ROSAT} observations of this cluster. %K Stars: Variables: {delta} Scuti %K Stars: Variables: Other %R 1998PASP..110..810V %F ori/PASPv110n749 %J-820 %T Color-Color Relations for Red Giants in Star Clusters. %A von Braun Kaspar %A Chiboucas Kristin %A Minske Jocelyn Kelly , %A Salgado Jos\'e Francisco %I Department of Astronomy, University of Michigan, Ann Arbor, MI 48109-1090; (kaspar@astro.lsa.umich.edu), (kristin@astro.lsa.umich.edu), (kelly@astro.lsa.umich.edu), (salgado@astro.lsa.umich.edu) and %A Worthey Guy %I Department of Physics and Astronomy, St. Ambrose University, 518 West Locust Street, Davenport, IA 52803; (gworthey@saunix.sau.edu) %B New Johnson-Cousins {\em UBVRI} photometry of giants in globular clusters is combined with {\em JHK} photometry on the CIT system to produce color sequences for giants from the globular clusters M3, M5, M13, and M92. {\em UBVRI} data are also presented for giants in the metal-rich open cluster NGC 6791. These data fill a gap in the literature, especially for the {\em R} and {\em I} bands. We provide the empirical relations between broadband colors for various [Fe/H] values for metal-poor giants. The color sequences for U-B and B-V show clear separations for different [Fe/H] values. We also find weak, although unexpected, metallicity dependences of V-R, V-I, and J-K colors. H-K is metal insensitive. The above colors are plotted as a function of V-K, and a literature V-K-T_eff_ relation is given. %K Galaxy: Globular Clusters: Individual: Messier Number: M3 %K Galaxy: Globular Clusters: Individual: Messier Number: M5 %K Galaxy: Globular Clusters: Individual: Messier Number: M13 %K Galaxy: Globular Clusters: Individual: Messier Number: M92 %K Galaxy: Open Clusters and Associations: Individual: NGC Number: NGC 6791 %K Stars: Fundamental Parameters %K Stars: Population II %R 1998PASP..110..821W %F ori/PASPv110n749 %J-826 %T Metallicities of Two Distant Globular Clusters from Spectra of Moderate Dispersion. %A Wachter Stefanie %A Wallerstein George (1) %I Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195-1580 %A Brown Jeffery A. %I Program in Astronomy, Washington State University, Pullman, WA 99164-3113 and %A Oke J.B. %I Palomar Observatory, California Institute of Technology, Pasadena, CA 91125; and Dominion Astrophysical Observatory, Herzberg Institute for Astrophysics, Victoria, BC, V8X 4M6, Canada %B We have used model atmospheres and spectrum synthesis to analyze medium resolution, moderate signal-to-noise, blue spectra of three stars in each of the globular clusters NGC 7006 and NGC 6229 for metallicity and carbon abundance. Both clusters are known to have intermediate metallicity, but NGC 7006 has a reddish horizontal branch, while NGC 6229 has a blue horizontal branch. We find that [MMH]=-1.6 for NGC 7006 and [MMH]=-1.4 for NGC 6229, with uncertainties near +/-0.1. In NGC 7006 carbon is depleted, presumably by CN cycling, so that [CMFe]=-0.71. Our [C/Fe] ratio, as derived for stars with T_eff_~4200 K, agrees with the [C/Fe] ratio found by Friel et al. for stars with {\em T}_eff_ between 4500 and 4700 K. This shows that the stars in NGC 7006 have not suffered additional mixing as they advance up the giant branch from 4700 K to the red giant tip. For NGC 6229 we derive [CMFe]=-0.56. We find evidence for a scatter in [C/Fe], indicating differing degrees of carbon depletion from star to star. %K Galaxy: Halo %K Galaxy: Globular Clusters: Individual: NGC Number: NGC 6229 %K Galaxy: Globular Clusters: Individual: NGC Number: NGC 7006 %K Stars: Abundances %I (1) Guest Investigator, Palomar Observatory, California Institute of Technology; (wachter@astro.washington.edu). %R 1998PASP..110..827W %F ori/PASPv110n749 %J-830 %T {\em EUVE} Pointed Observations of the {beta} Canis Majoris Interstellar Tunnel. %A Welsh B.Y. %A Vallerga J.V. , %A McDonald K. %I Eureka Scientific, 2452 Delmer Street, Oakland, CA 94602; (eureka@netcom.com), (bwelsh@ssl.berkeley.edu), (jvv@cea.berkeley.edu), (kelley@cea.berkeley.edu) %B We present results from extended pointings of the {\em EUVE} scanner telescopes in the direction of the rarefied interstellar tunnel toward the star {beta} CMa. Five sources were detected, each of which subsequently proved to be caused by ultraviolet leaks in the {\em EUVE} short-wavelength filters. Our initial expectation was to detect many new EUV sources in the 80 deg^2^ region of very low neutral interstellar hydrogen column density covered by these extended pointings. However, no EUV sources were detected. This result is consistent with a source of short-wavelength EUV opacity, providing indirect evidence for the presence of highly ionized (coronal) gas at distances of more than 5 pc in the line of sight toward this region of anomalous interstellar absorption. %K ISM: Bubbles %K ISM: General %R 1998PASP..110..831N %F ori/PASPv110n749 %J-836 %T New Measurements of the Expansion of the Crab Nebula. %A Nugent Richard L. %I P.O. Box 12888, Houston, TX 77217; (rnugent@ghg.net) %B Published images of the Crab Nebula have been scanned and measured to derive proper motions, the age of the nebula, and its point of origin. Astrometric reductions provided rms errors ranging from 0".14 to 0".31 in both axes for a given image. Proper motions of 50 optical filaments with a 53 yr baseline projected backward indicates the mean date of the supernova event as A.D. 1130+/-16 yr, in good agreement with previous investigations by Trimble and Wyckoff & Murray but 76 yr after the reported outburst recorded by the Chinese astronomers in A.D. 1054. This result confirms the well-known acceleration in the Crab's expansion. The image-scanning technique demonstrates that accurate astrometric reductions can be achieved on a personal computer. %R 1998PASP..110..837R %F ori/PASPv110n749 %J-840 %T Maximum Gain and Efficiency of Adaptive Optics Systems. %A Roddier Fran\c{c}ois %I Institute for Astronomy, 2680 Woodlawn Drive, Honolulu, HI 96822; (roddier@ifa.hawaii.edu) %B A definition is given for the efficiency of an adaptive optics (AO) system. An expression is derived that allows the efficiency of an AO system to be simply estimated. Estimates are derived for the efficiency of several AO systems currently used in astronomy. The advantages of building high-efficiency systems are emphasized. %K Instrumentation: Miscellaneous %R 1998PASP..110..841G %F ori/PASPv110n749 %J-847 %T Development of a Machine-cut Metal Grating for Near-Infrared Spectroscopy. %A Goto Miwa %A Motohara Kentaro %A Imanishi Masatoshi %A Sugiyama Kouji %A Tomita Kazuhisa %A Iwamuro Fumihide , %A Maihara Toshinori %I Department of Physics, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo, Kyoto 606-8502, Japan: (mgoto@cr.scphys.kyoto-u.ac.jp) %B We have developed a special grating capable of producing an echellogram (a spectrum arranged in raster form) in the 30th or even higher order in the near-infrared wavelength region. The grating substrate is made of an aluminum alloy that has been carved mechanically with a high-precision shaving machine. The optical efficiency, measured with a special spectrophotometer at about 2 {mu}m, is ~70%. The diffuse light component, possibly attributable to scattering on the grating surface, has been estimated to be at most ~5% when the grating is incorporated in an actual spectrograph system. The measured efficiency of the fabricated grating is compared with that given by a numerical analysis. The comparison shows remarkable agreement in both the optical efficiency and the distribution of energy diffracted to various orders. %K Instrumentation: Spectrographs %R 1998PASP..110..848G %F ori/PASPv110n749 %J-862 %T Location Estimators for Interferometric Fringes. %A Gai M. %I Astronomical Observatory of Torino, Strada Osservatorio, 20, I-10025 Pino T.se (TO), Italy; (gai@to.astro.it) %A Casertano S. %I Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218; and The Johns Hopkins University; (stefano@stsci.edu) %A Carollo D. %A Lattanzi M.G. %I Astronomical Observatory of Torino, Strada Osservatorio, 20, I-10025 Pino T.se (TO), Italy; (carollo@to.astro.it), (lattanzi@to.astro.it) %B Future global astrometry missions have targeted the determination of positions, parallaxes, and annual proper motions to the 10 {mu}as level. This can be achieved through the use of fringe imaging interferometers, possibly featuring wide fields of view (e.g., Fizeau configurations). The basic location information is to be extracted from the fringe pattern by proper implementation of the detection system and proper exploitation of the focal plane data. The sampling resolution requirements are a key trade-off issue between science and engineering: therefore, fringe acquisition by means of realistic detectors and the resulting accuracy in photocenter location is discussed herein. The location performance is described as a {chi}^2^ minimization problem; the resulting expressions are then evaluated in analytical form and by means of a Monte Carlo simulation, whch provide good agreement. In order to achieve the limiting interferometer accuracy, 8-10 pixels per fringe period are required, whereas a sampling resolution of 4-5 pixels per period provides a 30% degradation. We evaluate the location accuracy degradation induced by progressively reduced fringe visibility and increasing noise level. The former provides a smooth performance reduction, acceptable to a wide extent; read-out noise is critical because the fringe pattern signal is recorded over many pixels, each providing a comparable contribution to the overall noise. %K Instrumentation: Detectors %K Instrumentation: Interferometers %K Methods: Data Analysis %K Techniques: Image Processing %R 1998PASP..110..863P %F ori/PASPv110n749 %J-878 %T A Stellar Spectral Flux Library: 1150-25000 {AA}. %A Pickles A.J. %I Institute for Astronomy, University of Hawaii, Hilo, HI 96720; (pickles@ifa.hawaii.edu) %B A stellar spectral flux library of wide spectral coverage and an example of its application are presented. The new library consists of 131 flux-calibrated spectra, encompassing all normal spectral types and luminosity classes at solar abundance, and metal-weak and metal-rich F-K dwarf and G-K giant components. Each library spectrum was formed by combining data from several sources overlapping in wavelength coverage. The SIMBAD database, measured colors, and line strengths were used to check that each input component has closely similar stellar type. The library has complete spectral coverage from 1150 to 10620 {AA} for all components and to 25000 {AA} for about half of them, mainly later types of solar abundance. Missing spectral coverage in the infrared currently consists of a smooth energy distribution formed from standard colors for the relevant types. The library is designed to permit inclusion of additional digital spectra, particularly of non-solar abundance stars in the infrared, as they become available. The library spectra are each given as {\em F}_{lambda}_ versus {lambda}, from 1150 to 25000 {AA} in steps of 5 {AA}. A program to combine the library spectra in the ratios appropriate to a selected isochrone is described and an example of a spectral component signature of a composite population of solar age and metallicity is illustrated. The library spectra and associated tables are available as text files by remote electronic access. %K Atlases %K Stars: General %K Galaxies: Stellar Content %R 1998PASP..110..879H %F ori/PASPv110n749 %J-879 %T Multiwavelength Observations of Quasars and Their Environments. (Dissertation Summary). %A Hooper Eric J. %I Current address: Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS 83, Cambridge, MA 02138; (ehooper@cfa.harvard.edu)Thesis work conducted at Steward Observatory, University of Arizona, Tucson, AZ 85721Ph.D. dissertation directed by Christopher D. Impey; Ph.D. degree awarded 1997 %R 1998PASP..110..880H %F ori/PASPv110n749 %J-880 %T An Optical/Near-Infrared Study of Quasar Environments. (Dissertation Summary). %A Hall Patrick Brian %I Current address: Department of Astronomy, University of Toronto, 60 St. George Street, Toronto, Ontario, M5S 3H8, Canada; (hall@astro.utoronto.ca)Thesis work conducted at Steward Observatory, University of Arizona, Tucson, AZ 85721Ph.D. dissertation directed by: Richard F. Green; Ph.D. degree awarded: 1998 %R 1998PASP..110..881V %F ori/PASPv110n749 %J-881 %T Analysis of Three Fast Oxygen-Neon-Magnesium Novae. (Dissertation Summary). %A Vanlandingham Karen M. %I Current address: Department of Physics and Astronomy, Arizona State University, Tempe, AZ 85287-1504; (karenv@suelee.la.asu.edu)Thesis work conducted at Department of Physics and Astronomy, Arizona State University, Tempe, AZ 85287-1504Ph.D. thesis directed by Sumner Starrfield; Ph.D. degree awarded 1997 %R 1998PASP..110..882D %F ori/PASPv110n749 %J-882 %T Supernovae and Stellar Wind Interaction with the Ambient Medium. (Dissertation Summary). %A Dwarkadas Vikram V. %I Current address: Astronomy Department, University of Washington, Box 351580, Seattle, WA 98195-1580 (vikram@astro.washington.edu)Thesis work conducted at Astronomy Department, University of Virginia, P. O. Box 3818, Charlottesville, VA 22903-0818Ph.D. thesis directed by Roger A. Chevalier; Ph.D. degree awarded 1997