Search Publications
Coronal radio sounding with Ulysses: dual-frequency phase scintillation spectra in coronal holes and streamers.
Bird, M. K.; Karl, J.; Paetzold, M.
Dual-frequency Doppler measurements of the Ulysses downlink carrier signals were recorded during the spacecraft's 1995 solar conjunction. In this paper we present power spectra derived from phase fluctuations of the radio signals passing through the corona for different solar latitudes. It is possible to (a) distinguish clearly between spectra for…
Analysis of the ISOPHOT FIR maps of M51 and M101.
Lemke, D.; Telesco, C. M.; Kinkel, U. +6 more
The far-IR ISOPHOT maps of the spiral galaxies M51 and M101 at 60, 100, and at 175µm are analysed. For all areas in these galaxies the spectral energy distributions can be fitted with a single-temperature emission curve. Colours and dust temperatures were estimated for interesting sub-fields. The temperatures vary between 33K for HII regions…
A study on the nature of the peculiar supergiant HD 101584.
Waters, L. B. F. M.; Lamers, H. J. G. L. M.; Trams, N. R. +3 more
We present a study of low- and high-resolution ultraviolet, high-resolution optical CAT/CES spectra and ultraviolet, optical and infrared photometry of the peculiar supergiant HD 101584. From the photometry we learn that the ultraviolet and optical energy distribution cannot be fitted in a consistent way and we need a model in which the UV and opt…
A Joint Analysis of High-Energy Neutrons and Neutron-Decay Protons from a Flare
Vainio, R.; Torsti, J.; Usoskin, I. G. +2 more
A joint analysis of neutron monitor and GOES data is performed to study the production of high-energy neutrons at the Sun. The main objects of the research are the spectrum of >50 MeV neutrons and a possible spectrum of primary (interacting) protons which produced those neutrons during the major 1990 May 24 solar flare. Different possible scena…
The Ultraviolet Spectrum of DQ Herculis: Detection of Line and Continuum Pulsation
Anderson, Scott F.; Margon, Bruce; Downes, Ronald A. +1 more
The old nova DQ Herculis was observed with the Hubble Space Telescope (HST) Faint Object Spectrograph (FOS) in the 1150-2500 Å range. Spectra were taken with a time resolution of 4.08 s, allowing a search for pulsations of the UV light at the 71 s white dwarf spin period, analogous to those long known to be present in visible light. The integrated…
Coronal radio sounding with Ulysses: solar wind electron density near 0.1AU during the 1995 conjunction.
Bird, M. K.; Asmar, S. W.; Paetzold, M. +2 more
Dual-frequency ranging measurements were recorded for a three-week interval during the 1995 solar conjunction of the Ulysses spacecraft. The unusual occultation geometry resulting from the high inclination Ulysses orbit enabled coronal radio sounding from the solar South Pole to the heliographic equator at solar ray path offsets near 0.1AU. The el…
Anticorrelation of Variability Amplitude with X-Ray Luminosity for Active Galactic Nuclei
Abramowicz, Marek A.; Bao, Gang
The bright-spot model for the short-term X-ray variability of active galactic nuclei predicts that, statistically, sources with larger luminosities should have smaller variability amplitudes. This quantitatively agrees with the analysis of the observational data from 12 high-quality EXOSAT long looks performed by Lawrence & Papadakis.
Damped LY alpha Absorbers as Tracers of the Evolution of the Mass Spectrum of Interstellar Matter in the Galaxy Population
Turnshek, David A.; Khersonsky, Valery K.
A generally accepted approach to the interpretation of the damped Lyα absorption systems seen in QSO spectra is to attribute them to cases in which the observer's sight line passes through high column density gaseous disks of galaxies, i.e., spiral galaxies or the progenitors of spirals. Here we consider an alternative natural possibility, consist…
Ultraviolet and Visible Spectropolarimetry of the Red Rectangle and HD 44179
Sitko, Michael L.; Reese, Marty D.
We present the first ultraviolet and visible spectropolarimetry of the biconical nebula the Red Rectangle and its associated binary HD 44179. These observations were made between 1992 November and 1995 November using the Faint Object Spectrograph on board the Hubble Space Telescope and two separate ground-based observations. These new data gives m…
ISO observations of hot dust in the nucleus of the S0 galaxy NGC 3998.
Rupen, M. P.; Fich, M.; Knapp, G. R. +2 more
ISOCAM maps of the Seyfert 1 S0 galaxy NGC 3998 between 4.5µm and 15µm detect both extended emission from the bulge stars and strong point source emission from the nucleus. The inner regions of NGC 3998 appear to contain a few thousand solar masses of warm (~200K) dust, probably associated with the AGN.