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Wide Field Planetary Camera 2 Imaging of Young Clusters in the Magellanic Clouds
Da Costa, G. S.; Bessell, M. S.; Keller, Stefan C.
We have carried out Wide Field Planetary Camera 2 (WFPC2) F160BW, F555W, and F656N imaging of four young populous clusters: NGC 330, in the Small Magellanic Cloud, and NGC 1818, 2004, and 2100, in the Large Magellanic Cloud. We report photometric results for these four clusters, including identification using photometric colors of the cluster Be s…
A Keck Survey of Gravitational Lens Systems. I. Spectroscopy of SBS 0909+532, HST 1411+5211, and CLASS B2319+051
Blandford, R. D.; Fassnacht, C. D.; Readhead, A. C. S. +2 more
We present new results from a continuing Keck program designed to study gravitational lens systems. We have obtained redshifts for three lens systems, SBS 0909+532, HST 1411+5211, and CLASS B2319+051. For all of these systems, either the source or lens redshift (or both) has been previously unidentified. Our observations provide some of these miss…
Absolute magnitudes of OB and Be stars based on Hipparcos parallaxes
Wegner, W.
Absolute visual magnitudes of OB stars are determined from Hipparcos parallaxes using a sample of 1207 unreddened and 441 reddened stars of luminosity classes V-IV, III, Ia and Iab-Ib-II. The value of total-to-selective extinction R for reddened stars was calculated from near-infrared photometry. The new MV calibration is compared with …
ISO-SWS observations of pure rotational H_2O absorption lines toward Orion-IRc2
de Graauw, Th.; Feuchtgruber, H.; van Dishoeck, E. F. +4 more
First detections of thermal water vapor absorption lines have been made toward Orion IRc2 using the Short Wavelength Spectrometer (SWS) on board the Infrared Space Observatory (ISO). Grating spectra covering wavelengths 25-45 mu m yield 19 pure rotational lines, originating from energy levels 200-750 K above ground. Fabry-Perot spectra of 5 transi…
Deep Hubble Space Telescope STIS Color-Magnitude Diagrams of the Dwarf Irregular Galaxy WLM: Detection of the Horizontal Branch
Gregg, Michael D.; Minniti, Dante; Goudfrooij, Paul +3 more
We have obtained V- and I-band photometry for 1886 stars down to I=27 and V=28 in the field of the dwarf irregular galaxy WLM, using deep Space Telescope Imaging Spectrograph (STIS) CL- and LP-band images taken in the parallel mode with the Hubble Space Telescope. The photometry is used to study the horizontal branch identified in WLM. The horizon…
The Narrow-Line Region in the Seyfert 2 Galaxy NGC 3393
Ferland, G. J.; Wilson, Andrew S.; Netzer, Hagai +2 more
The narrow-line region (NLR) of the Seyfert 2 galaxy NGC 3393 is dominated by a symmetric structure which appears as S-shaped arms in Hubble Space Telescope (HST) images. These arms, which occupy the central few arcseconds of the nucleus, border a linear, triple-lobed radio source. We use HST imaging and spectra, ground-based optical images, long-…
Magellanic Cloud-Type Interstellar Dust along Low-Density Sight Lines in the Galaxy
Gordon, Karl D.; Clayton, Geoffrey C.; Wolff, Michael J.
We have studied the UV extinction properties along 30 Galactic sight lines using data from the International Ultraviolet Explorer archive that have never been previously examined. These distant (d>1 kpc) sight lines were selected to investigate the distribution and physical conditions of gas located in low-density regions of the Galactic disk a…
High-Velocity Collimated Outflows in Planetary Nebulae: NGC 6337, HE 2-186, and K4-47
Corradi, Romano L. M.; Gonçalves, Denise R.; Villaver, Eva +4 more
We have obtained narrowband images and high-resolution spectra of the planetary nebulae NGC 6337, He 2-186, and K4-47 with the aim of investigating the relation between their main morphological components and several low-ionization features present in these nebulae. The data suggest that NGC 6337 is a bipolar PN seen almost pole-on, with polar vel…
Astrometric radial velocities. II. Maximum-likelihood estimation of radial velocities in moving clusters
Lindegren, Lennart; Madsen, Søren; Dravins, Dainis
Accurate proper motions and trigonometric parallaxes of stars in nearby open clusters or associations permit to determine their space motions relative to the Sun, without using spectroscopy for their radial-velocity component. This assumes that the member stars share the same mean velocity vector, apart from a (small) random velocity dispersion. W…
HD 209458 planetary transits from Hipparcos photometry
Arenou, F.; Robichon, N.
During its 39-month mission, Hipparcos observed the star {{