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The Hubble Space Telescope Quasar Absorption Line Key Project. II. Data Calibration and Absorption-Line Selection
Turnshek, David A.; Schneider, Donald P.; Savage, Blair D. +10 more
We present the observational and data processing aspects of the Hubble Space Telescope Quasar Absorption Line Key Project. Topics discussed include the observational technique, calibration of the data, software that simulates the data, the automated procedure used to identify and characterize the absorption features, and the determination of the s…
The Ionization Cones in the Seyfert Galaxy NGC 5728
Krolik, J. H.; Wilson, A. S.; Heckman, T. M. +2 more
We report high-resolution (0.1") observations of the Seyfert 2 galaxy NGC 5728 with the Hubble Space Telescope. Images have been obtained in the light of [O III] λλ4959, 5007, Hα+[N II] λλ6548, 6583 and green and red continua. The emission-line images reveal a spectacular biconical structure with overall extent 1.8 kpc. The two cones share a commo…
Abundance of Interstellar Carbon toward zeta Ophiuchi
Ebbets, Dennis C.; Savage, Blair D.; Cardelli, Jason A. +1 more
We report on the detection of the weak intersystem transition of semiforbidden C II 2325 A in the sight line toward Zeta Oph using the Ech-B mode of the Goddard High-Resolution Spectrograph. The measured equivalent width of the semiforbidden C II line is W(lambda) = 0.52 +/- 0.12 mA, implying a C II column density of 1.80 (+/- 0.42) x 10 exp 17 at…
Disappearance of the heliospheric sector structure at Ulysses
Balogh, A.; Tsurutani, B. T.; Forsyth, R. J. +6 more
In May, 1993, the heliospheric current sheet (HCS) ceased to be seen by the Ulysses spacecraft at a heliocentric latitude of ∼30° S and distance of 4.7 AU. The disappearance of the HCS coincided with the solar wind speed remaining >560 km/s and with the disappearance of one of four interaction regions previously seen on each solar rotation. The…
Ultraviolet Spectra of QSOs, BL Lacertae Objects, and Seyfert Galaxies
Turnshek, David A.; Lanzetta, Kenneth M.; Sandoval, Jennifer
Motivated by the possibility of detecting strong absorption features toward extragalactic background objects, we present optimally extracted and co-added IUE spectra of QSOs, BL Lac objects, and Seyfert galaxies. These spectra together with those presented (in a similar work) by Kinney et al. form an essentially complete sample of the SWP, LWP, an…
The extended formaldehyde source in comet P/Halley
Eberhardt, P.; Meier, R.; Krankowsky, D. +1 more
The Neutral Mass Spectrometer on the Giotto spacecraft measured the neutral and ion composition in the coma of comet P/Halley. In the ion mass spectra, the 31 amu/e peak is dominated by the protonated formaldehyde ion H3CO+ and can be used to calculate the H2CO density. The radial profile of the amplitude of the 31…
ROSAT studies of the composition and structure of DA white dwarf atmospheres.
Barstow, M. A.; Koester, D.; Sansom, A. E. +7 more
We present here a detailed study of a sample of hot I)A white dwarfs detected in the EUV and soft X-ray bands by ROSAT during its all-sky survey. The survey data are combined with additional ROSAT pointed-phase observations, earlier EXOSAT results and the available optically determined effective temperatures and gravities. We show that the spectra…
Multiwavelength Monitoring of the BL Lacertae Object PKS 2155-304. I. The IUE Campaign
Maraschi, L.; Chiappetti, L.; Tagliaferri, G. +26 more
Daily monitoring of PKS 2155 - 304 with the IUE satellite throughout 1991 November has revealed dramatic, large-amplitude, rapid variations in the ultraviolet flux of this BL Lac object. Many smaller, rapid flares are superposed on a general doubling of the intensity. During the 5^d^ period when sampling was roughly continuous, the rapid flaring h…
The Hubble Space Telescope Snapshot Survey. IV. A Summary of the Search for Gravitationally Lensed Quasars
Gould, A.; Maoz, D.; Meylan, G. +7 more
We report the concluding results of the HST Snapshot Survey for gravitationally lensed quasars. New observations of 153 high-luminosity z > 1 quasars are presented, bringing to 498 the total number of quasars observed in the survey. The new observations do not reveal new candidates for gravitational lensing. We present tables summarizing all of…
Further probing of the X-ray source in NGC 4151 : new constraints on the nuclear geometry.
Sokoloski, J. L.; Yamauchi, M.; Warwick, R. S. +4 more
We report on the results of new Ginga observations of the archetypal Seyfert galaxy, NGC 4151, performed over an 18-month period between early 1990 and mid-1991. The present programme complements earlier extensive monitoring of this source in the medium-energy X-ray band by both EXOSAT and Ginga to give a combined data set of some 36 separate obse…