Search Publications
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…
Measurements of the solar wind over a wide range of heliocentric distances - a comparison of results from the first three Whole Sun Months
Thompson, B. J.; Biesecker, D. A.; Lazarus, A. J. +9 more
Co-ordinated observations of the Sun and inner heliosphere using a large number of space- and ground-based instruments were carried out in August-September 1996, August 1998 and August-September 1999 as the first, second and third Whole Sun Months. These observations provided unprecedented cover of the Sun and inner heliosphere at solar minimum (1…
The HE II Emitting Nebula N44C in the Large Magellanic Cloud: Optical/Ultraviolet Spectroscopy of the Nebula and Its Ionizing Star
Garnett, Donald R.; Chu, You-Hua; Galarza, Vanessa C.
We present HST spectroscopy and imaging, along with new ground-based spectroscopy and ROSAT HRI imaging, of the He II emitting nebula N44C and its ionizing star. A GHRS spectrogram of the ionizing star yields a spectral type of about O7 for the star. The lack of P Cygni profiles for Si IV and C IV indicates that the star is not a supergiant. The n…
A Search for Exozodiacal Dust and Faint Companions near Sirius, Procyon, and Altair with the NICMOS Coronagraph
Brown, Michael E.; Kuchner, Marc J.
We observed Sirius, Altair, and Procyon with the NICMOS coronagraph on the Hubble Space Telescope to look for scattered light from exozodiacal dust and faint companions within 10 AU from these stars. We did not achieve enough dynamic range to surpass the upper limits set by IRAS on the amount of exozodiacal dust in these systems, but we did set st…
Does the tachocline show solar cycle related changes?
Basu, Sarbani; Schou, Jesper
The tachocline at the base of the convection zone is generally believed to be the seat of the solar dynamo. Here we investigate whether the tachocline shows any detectable change using several 72 day time-series of the Michelson Doppler Imager (MDI) Medium-l data. We do not find any clear evidence of change with time.
UV spectroscopy of the peculiar binary V Sagittae in a low state
Wood, Janet H.; Lockley, J. J.
In this paper we present the first phase-resolved, high-resolution, UV spectroscopy of V Sge. HST GHRS observations were obtained covering 1.5 orbital cycles of V Sge in a low state. We covered the Heii 1640 line and the Civ 1550 doublet alternately, and also obtained one spectrum covering Mgii 2800. We create continuum and line flux light curves …
Temperature Structure of the Quiet Corona: An SXT-SUMER Discrepancy
Lemen, J.; Sturrock, P. A.; Wolfson, Richard +2 more
The Soft X-ray Telescope (SXT) on Yohkoh and the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer on the Solar and Heliospheric Observatory (SOHO) are both capable of providing measures of temperature in the solar corona. A recent SUMER-based study of a quiet coronal region suggests an isothermal plasma in the range from 1.…
FOS observations of four NLS1s
Goodrich, Robert W.
Ultraviolet through optical spectroscopy of four NLS1s shows strong absorption features in the high-ionization UV resonance lines such as C IV, N V, and Si IV. Mg II is not absorbed. The absorption could originate in the warm absorber.
EC 11481-2303: A Peculiar Hot High-Gravity Pre-White Dwarf
O'Donoghue, Darragh; Sion, E. M.; Holberg, J. B. +6 more
We report the discovery of a peculiar new hot high-gravity predegenerate star, EC 11481-2303 from the Edinburgh-Cape Blue Object Survey, based upon the analysis of far-UV International Ultraviolet Explorer (IUE) echelle and low-resolution spectra and an optical spectrum. The IUE spectra reveal the presence of far-UV photospheric/circumstellar high…