Search Publications
A spectroscopic study of the magnetic CP-star HR 1094
Wahlgren, G. M.; Nielsen, K.
The chemically peculiar star
The linear force-free field in a spherical shell using a new method to determine the coefficients of the eigenfunction expansion
Bromage, B. J. I.; Clegg, J. R.; Browning, P. K. +2 more
The linear force-free field of a plasma in between spherical shells is found allowing for inhomogeneous boundary conditions. A three-dimensional solution is found by analysis and used as a benchmark to test a solution in terms of an expansion of eigenfunctions where the coefficients are determined by a new method. Alternative methods are also appl…
Possible emission lines from the gaseous beta Pictoris disk
Feldman, P. D.; Lecavelier des Etangs, A.; Ferlet, R. +6 more
We present the results of exploratory HST observations to detect the emission lines of ions in the beta Pictoris disk with the spectrograph slit placed off the star. Possible emission lines from Fe II have been detected at ~10-14erg cm-2 s-1 at 0.5'' from beta Pictoris, which would suggest a total Fe II density of …
Blue stragglers in open clusters. Part II
Drilling, J. S.; Andrievsky, S. M.; Schönberner, D.
We present the results of a spectroscopic study of blue straggler and main sequence B and A - type stars in the open clusters NGC 3496, NGC 6475, NGC 6633 and IC 2602. A detailed analysis based on Kurucz's atmosphere models showed that the main sequence stars rotate rather rapidly and differ from a normal (solar) metallicity for only a few light e…
A unified image of dust grains for the warped spiral galaxy in the merger Centaurus A
Sauvage, M.; Block, D. L.
A unified view of dust grains of all sizes and temperatures in Centaurus A has been generated by combining ISOCAM mid-infrared images with optical data. In our unified V-15mu m ratio image, a symmetrical bar-like structure and spiral arms of size 1.5 kpc surround the nucleus. We have overlaid the (H-K) model colour map of \cite{quillen93} and find…
Simulation of resonance scattering helioseismometer signals from spatially resolved images: Application to the GOLF instrument on SOHO
Henney, C. J.; García, R. A.; Ulrich, R. K. +3 more
A step in the analysis of the data from the GOLF (Global Oscillations at Low Frequency) instrument on SOHO (SOlar and Heliospheric Observatory, an ESA/NASA Mission) involves the calculation of the sensitivity of the GOLF signal to the velocity at each point on the solar surface. A successful model of this sort will permit the intercomparison of da…
Transition region and coronal structuring
Mathioudakis, M.; Keenan, F. P.; Phillips, K. J. H. +3 more
In this paper we examine regions of internetwork, network and bright network emission, observed in the quiet Sun with the Coronal Diagnostic Spectrometer (cds) onboard SoHO. The slopes of the emission measure distributions, between 5.4 <= log Te <= 6.0, are found to differ in each region, suggesting the presence of different atmos…
Hβ photometry of southern CP2 stars: is the uvbybeta luminosity calibration also valid for peculiar stars?
Vogt, N.; Paunzen, E.; Maitzen, H. M. +1 more
We present Hβ photometry of 233 southern CP2 stars (covering the magnetic Ap stars according to the definition by Preston 1974) brighter than V < 8.5 mag from the list of Bidelman & MacConnell (1973). Absolute magnitudes derived from this photometry together with already existing uvby photometry is confronted with Hipparcos results availabl…
Physical parameters of EUV explosive events
Doyle, J. G.; Pérez, M. E.
Previously published results of EUV explosive events and electron density enhancements in the solar transition region are revised. An attempt has been made to correlate both observational phenomena, and to associate the observed density enhancements to magnetic reconnection sites. The corresponding local magnetic field strength in these sites is e…
An estimation of the shape and temporal variation of the solar wind sonic, Alfvénic and fast magnetosonic surfaces
Moussas, X.; Exarhos, G.
In this work we find the shape and dimension of the solar wind transition surfaces, namely the slow (sonic), the fast magnetosonic and the Alfvén surface, as a function of heliospheric latitude using actual experimental data from Ulysses spacecraft during its first pole to pole journey. We also give the temporal variation of the radius of these su…