Search Publications
The RR Lyrae star period - K-band luminosity relation of the globular cluster M 3
Butler, D. J.
That the RR Lyrae star period - K-band luminosity relation is a promising tool as a distance indicator in the Milky Way and Local Group of galaxies is apparent on observational and theoretical grounds in the literature. Less clear is the sensitivity of the relation, and consequently the physics of horizontal branch stars, to differences in stellar…
Dependence of UV radiance of the quiet Sun on the solar cycle: Surface magnetic fields as the cause
Solanki, S. K.; Pauluhn, A.
The quiet-Sun UV radiance depends on the solar cycle, as shown by data collected by the SUMER spectrograph on the Solar and Heliospheric Observatory (SOHO). The cause of this dependence is still unclear. Here the hypothesis is tested for the He I 584 Å line that these variations are due to changes in the magnetic network. The quiet-Sun variability…
On the nature of extended EUV filaments
Heinzel, P.; Anzer, U.
This paper describes the properties of extended EUV filaments and the theoretical modelling of them. We summarise the general aspects of the depression of EUV-line emission and give an interpretation of recent filament observations in transition-region and coronal lines. The EUV filament was found to be located relatively high in the corona (at le…
ISOCAM-CVF imaging of M 16
Pilbratt, G. L.; White, Glenn J.; Urquhart, J. S. +1 more
We present ISOCAM observations (5-17 mu m) of the HST M 16 field, including the striking elephant trunk structures. The spectroscopic data have been obtained using the ISOCAM-CVF low-resolution mode, having a spectral resolution of ~ 40 (lambda /Delta lambda ) and a pixel size of 6''. The spectra show a combination of Unidentified Infra…
Past and recent observations of the solar upper atmosphere at vacuum-ultraviolet wavelengths
Wilhelm, Klaus
Our understanding of the high-temperature solar atmosphere is to a large extent based on spectroscopic observations of emission lines and continuum radiation in the vacuum-ultraviolet (VUV) wavelength range of the electromagnetic spectrum. In addition, important contributions stem from soft X-ray measurements. The VUV radiation is produced by tran…
Effect of anisotropic velocity distribution on the linear polarization of coronal lines. Does the ion cyclotron exist in the inner corona?
Solanki, S. K.; Raouafi, N. -E.
The effect of an anisotropic velocity field distribution of scattering ions on the polarization parameters of a spectral line emitted by resonance scattering is considered. The anisotropy of the velocity field distribution can be interpreted in terms of the ion-cyclotron effect that is believed to influence some heavy ions in the solar corona. We …
Upgrades to the Flagstaff Astrometric Scanning Transit Telescope: A Fully Automated Telescope for Astrometry
Harris, Hugh C.; Vrba, Frederick J.; Munn, Jeffrey A. +13 more
The Flagstaff Astrometric Scanning Transit Telescope (FASTT) is a fully automated telescope that takes about 41,000 CCD frames of data a year for various research projects. All aspects of the telescope's operation have been automated (e.g., target selection, observing, reduction of data, and collation of results), and manpower needs are now under …
Models for the positive latitude e{-}e{+} annihilation feature
Knödlseder, J.; Guessoum, N.; Jean, P. +1 more
Galactic maps of e-e+ annihilation radiation based on CGRO-OSSE, SMM and TGRS data have indicated the existence of an extended component at positive Galactic latitudes (l~ -2 deg, b~ 7 deg), in addition to the emission from the galactic bulge and disk (Purcell et al. \cite{Purcell97}; Cheng et al. \cite{…
The Long Aftermath of Superoutbursts: STIS Results on AL Comae 5.5 Years Past Outburst
Szkody, Paula; Howell, Steve B.; Sion, Edward M. +2 more
The Space Telescope Imaging Spectrograph (STIS) was used to obtain the ultraviolet spectrum of AL Comae 5.5 yr past its 1995 April superoutburst. The spectrum can be fitted by a model of a logg=8+/-0.5 white dwarf with a temperature of 16,300+/-1000 K. Surprisingly, the flux distribution is exactly the same as the Faint Object Spectrograph data ob…
GRB 021219: The first Gamma-Ray Burst localized in real time with IBAS
Götz, D.; Mereghetti, S.; von Kienlin, A. +5 more
On December 19, 2002, during the Performance and Verification Phase of INTEGRAL, a Gamma-Ray Burst (GRB) has been detected and localized in real time with the INTEGRAL Burst Alert System (IBAS). Here we present the results obtained with the IBIS and SPI instruments. The burst had a time profile with a single peak lasting about 6 s. The peak spectr…