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ORFEUS II echelle spectra: on the influence of iron-group line blanketing in the Far-UV spectral range of hot subdwarfs
Deetjen, J. L.
We present an analysis of the subdwarf O star Feige 67 with a fully metal-line blanketed NLTE model atmosphere based on high-resolution Far-UV (912-2000 Å) and Near-UV (2000-3400 Å) spectra from new ORFEUS II echelle observations and the IUE final archive. The Far- UV spectra are heavily blanketed by iron and nickel lines, preventing the detection…
Precise Interplanetary Network Localization of the Bursting Pulsar GRO J1744-28
Cline, T.; Hurley, K.; Kouveliotou, C. +8 more
We analyze 426 observations of the bursting pulsar GRO J1744-28 by Ulysses and BATSE. Triangulating each burst and statistically combining the triangulation annuli, we obtain a 3 σ error ellipse whose area is 532 arcsec2. The accuracy of this statistical method has been independently verified with observations of the soft gamma repeater…
Hubble Space Telescope imaging survey of sub-mJy star-forming galaxies - I. Morphologies at z~0.2
Mobasher, Bahram; Serjeant, Stephen; Oliver, Seb +1 more
We present the first results of our Hubble Space Telescope HST WFPC2 F814W snapshot imaging survey, targeting virtually all sub-mJy decimetric radio-selected star-forming galaxies. The radio selection at ~1GHz is free from extinction effects and the radio luminosities are largely unaffected by AGN contamination, making these galaxies ideal tracers…
Solar equatorial plasma rotation: a comparison of different spectroscopic measurements
Schmidt, W.; Wöhl, H.
We present solar equatorial rotation velocities measured with two different spectral lines (Fe I 557.6 nm and Ni I 676.8 nm) and two different spectrometers at the German Vacuum Tower Telescope (VTT) on Tenerife. The `classical' sidereal solar equatorial rotation velocity of about 2000 m/s has been confirmed. The results are compared with those fr…
Effect of magnetic discontinuities on the propagation of energetic particles: Ulysses observations of the onset of the March 1991 solar particle event
Balogh, A.; Forsyth, R. J.; Phillips, J. L. +5 more
We present observations of energetic ions from the Cosmic Ray and Solar Particle Investigation (COSPIN) and Heliospshere Instrument for Spectra Composition and Anisotropy at Low Energy (HISCALE) instruments on board the Ulysses spacecraft. We examine in detail the onset of energetic ions observed during the March 1991 series of solar events. Activ…
Double Stars in the Tycho-2 Catalogue
Mason, Brian D.; Makarov, Valeri V.; Wycoff, Gary L. +3 more
The Tycho-2 Catalogue provides astrometric and photometric information for 2.5 million stars. Within the Tycho-2 Catalogue, while there is no separate listing of double-star parameters, there is a wealth of double-star data. For all measured double-star systems, each component has its own entry in Tycho-2 (this corresponds to the Hipparcos ``doubl…
The Variability of Seyfert 1.8 and 1.9 Galaxies at 1.6 Microns
Rieke, G. H.; Alonso-Herrero, A.; Quillen, A. C. +4 more
We present a study of Seyfert 1.5-2.0 galaxies observed at two epochs with the Hubble Space Telescope (HST) at 1.6 µm. We find that unresolved nuclear emission from nine of 14 nuclei varies at the level of 10%-40% on timescales of 0.7-14 months, depending upon the galaxy. A control sample of Seyfert galaxies lacking unresolved sources and ga…
An Ultraviolet Fe II Image of SN 1885 in M31
Fesen, Robert A.; Hamilton, Andrew J. S.
Ultraviolet imaging of the remnant of supernova (SN) 1885 in M31 with the Hubble Space Telescope using the F255W filter on the WFPC2 reveals a dark spot of Fe II absorption at the remnant's known position in the bulge of M31. The diameter of the absorbing spot, ~0.5", is consistent with the 0.70"+/-0.05" diameter measured in the higher quality WFP…
Metal contamination analysis of the epitaxial starting material for scientific CCDs
Kemmer, J.; Strüder, L.; Krause, N. +4 more
Traces of unintentionally introduced titanium into a 3 k Ω cm float-zone epitaxial silicon at ultra low levels of 10 10 cm-3 were found to be the origin of charge transfer loss in pn-CCDs. We identified and backtracked the titanium impurity. The full-depletion design of the pn-CCD, a thin entrance window at the back of the CC…
Variable HST guide stars (I)
Zwintz, K.; Frandsen, S.; Kuschnig, R. +4 more
We have performed time series analyses on more than 4500 sets of Hubble Space Telescope (HST) Fine Guidance Sensor (FGS) data, obtained from about 3600 guide stars in the period from August 1992 to December 1995. We discuss here a subset of 20 stars that were found to be variable at a high confidence level. This subset contains all definite variab…