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The HIPPARCOS catalogue as a realisation of the extragalactic reference system
Zacharias, N.; Kozhurina-Platais, V.; Hemenway, P. D. +23 more
The paper describes the methods and observations by which the Hipparcos Catalogue was linked to the International Celestial Reference System (ICRS). The contributions of several groups represented in the authorship of this paper, using a variety of techniques, were synthesised in order to determine the global orientation and rotation (spin) of the…
Cataclysmic variables in the ROSAT PSPC All Sky Survey.
Verbunt, F.; Bunk, W. H.; Ritter, H. +1 more
91 cataclysmic variables from a sample of 162 systems with known or suspected binary periods were detected during the ROSAT XRT-PSPC All Sky Survey. Among the non-magnetic systems, the X-ray to optical/ultraviolet flux ratio decreases along the sequence SU UMa type - U Gem type - Z Cam type - UX UMa type, due mainly to variations in the optical/ul…
Evolution of Early-Type Galaxies in Distant Clusters: The Fundamental Plane from Hubble Space Telescope Imaging and Keck Spectroscopy
van Dokkum, Pieter G.; Franx, Marijn; Kelson, Daniel D. +2 more
We present new results on the fundamental plane of galaxies in two rich clusters, Cl 1358+62 at z = 0.33 and MS 2053-04 at z = 0.58, based on Keck and Hubble Space Telescope observations. Our new data triple the sample of galaxies with measured fundamental plane parameters at intermediate redshift. The early-type galaxies in these clusters define …
EUV Blinkers: The Significance of Variations in the Extreme Ultraviolet Quiet Sun
Harrison, Richard A.
A search for microflare activity in the extreme ultraviolet (EUV) quiet Sun using the Coronal Diagnostic Spectrometer (CDS) aboard the Solar and Heliospheric Observatory (SOHO) spacecraft has not resulted in the identification of microflare activity, but has resulted in the identification of a hitherto unknown phenomenon: enhancements of a factor …
Hubble Space Telescope Faint Object Spectroscope Spectroscopy of Localized Chemical Enrichment from Massive Stars in NGC 5253
Kobulnicky, Henry A.; Skillman, Evan D.; Walsh, J. R. +2 more
Optical and ultraviolet spectroscopy obtained with the Hubble Space Telescope Faint Object Spectrograph at three locations in the central H II complex of the amorphous starburst galaxy NGC 5253 confirms an apparent area of enhanced nitrogen abundance seen in ground-based studies. At two positions, N appears enhanced by a factor of 3 [log (N/O) = -…
A high deuterium abundance at redshift z = 0.7
Ferlet, R.; Vidal-Madjar, A.; Lemoine, M. +4 more
Of the light elements, the primordial abundance of deuterium relative to hydrogen, (D/H)p, provides the most sensitive diagnostic for the cosmological mass density parameter, ΩB. Recent high-redshift D/H measurements are highly discrepant, although this may reflect observational uncertainties,. The larger primordial D/H value…
The EXOSAT Data on GX 339-4: Further Evidence for an ``Intermediate'' State
Méndez, Mariano; van der Klis, Michiel
We have studied the fast timing and spectral behavior of the black hole candidate (BHC) GX 339-4 using all 1-20 keV EXOSAT ME data: the 1983 July, 1984 March, 1984 May, and 1985 April observations. In 1985 April, GX 339-4 was in a weak low state (0.03 × 10-9 ergs cm-2 s-1, 2-10 keV). The X-ray spectrum was a hard p…
Quasar Absorbing Galaxies at z <~ 1: Deep Imaging and Spectroscopy in the Field of 3C 336
Dickinson, Mark; Steidel, Charles C.; Sembach, Kenneth R. +2 more
We present very deep WFPC2 images and FOS spectroscopy from the Hubble Space Telescope (HST) together with numerous supporting ground-based observations of the field of the quasar 3C 336 (zem = 0.927). The observations are designed to investigate the nature of galaxies producing metal-line absorption systems in the spectrum of the QSO. …
Infrared Spectroscopy of Dust in the Diffuse Interstellar Medium toward Cygnus OB2 No. 12
de Graauw, Th.; Prusti, T.; van Dishoeck, E. F. +7 more
Observations made with the short-wavelength spectrometer of the Infrared Space Observatory are used to investigate the composition of interstellar dust in the line of sight to Cygnus OB2 No. 12, commonly taken as representative of the diffuse (low-density) interstellar medium. Results are compared with data for the Galactic center source Sgr A*. N…
The Dependence of the Circumnuclear Coma Structure on the Properties of the Nucleus
Rodionov, A. V.; Crifo, J. F.
A new step of development of the 3-D circumnuclear coma (“CNC”) model described in Crifoet al.(1995) is presented: now the gas and dust production are computed from an explicit dusty-ice sublimation model and a realistic dust mass spectrum is used. For the first time, (1) a clear distinction is made betweennucleus active area fraction gandactive s…