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The Structure of the Planetary Nebula IC 2149: A Jet or an Edge-On Ring?
López, J. A.; Torrelles, J. M.; Miranda, L. F. +4 more
A set of optical and radio observations of the peculiar planetary nebula (PN) IC 2149 is presented. A bow-shock-like feature towards the NE edge is first detected with the VLA-A, and is also confirmed with HST archive images. Optical spectroscopy leads to apparently contradictory results, leaving this object as a unique case among the planetary ne…
The effect of instrument limitations on the derivation of plasma flows from energetic ion anisotropies, with an application to Ulysses observations at Jupiter
Cowley, S. W. H.; Kolesnikova, E.
Plasma velocities determined from the anisotropies of energetic ions via the Compton-Getting effect have been important in studies of magnetospheric flows, particularly with regard to the magnetospheres of Jupiter and Saturn. In this paper we consider a range of issues concerned with the practical limitations of such measurements, and their effect…
The soft X-ray coronal mass ejection above solar limb of 1998 April 23
Chen, Xiao-juan
Using the observational materials of SXT/HXT aboard satellite Yohkoh and the Nobeyama Radioheliograph (NoRH) on 1998-04-23, a comprehensive study of the soft X-ray coronal mass ejection (CME) above solar SE limb shows that there were two magnetic dipolar sources (MDSs), one magnetic capacity belt (MCB) between the MDSs, one neutral current sheet (…
Cassini/VIMS observations of the moon
Sotin, C.; Brown, R. H.; Baines, K. H. +19 more
In this paper, we present preliminary scientific results obtained from the analysis of VIMS (Visible and Infrared Mapping Spectrometer) lunar images and spectra. These data were obtained during the Cassini Earth flyby in August 1999. Spectral ratios have been produced in order to derive lunar mineralogical maps. Some spectra observed at the north-…
Characteristics of Active Galactic Nuclei in the Ultraviolet
Kautsch, S. J.; Zeilinger, W. W.
A sample of UV spectra of the central region of 28 early-type galaxies with signatures of nuclear activity is produced by collecting spectra from the on-line archive of the International Ultraviolet Explorer (IUE) satellite mission. We present a comparison of line flux measurements and the spectral energy distribution (SED) of these objects. The r…
Fishing for Delta Scuti stars in the Hipparcos photometric database
Percy, J. R.; Gilmour-Taylor, G.
Lyman α intensities in a polar coronal hole from a 2D model
Poletto, G.; Noci, G.; Nicolosi, P. +1 more
We simulate the coronal H I Lyman α intensity for heliocentric distances between 1.5 and 2.5 R⊙, and latitudes between 90° (North pole) and 30°, making use of a 2D semiempirical coronal hole model. Observations are made with the UltraViolet Coronagraph Spectrometer (UVCS) on board the ESA-NASA solar satellite SOHO (SOlar and Heliospheri…
Variation of acoustic mode centroid frequencies over the solar cycle
Chaplin, W. J.; Elsworth, Y.; Appourchaux, T. +2 more
Together with a brief historical overview, we use high-quality helioseismic data collected by three different observational programmes during the declining phase of activity cycle 22, and a substantial portion of the rising phase of the current cycle (23), to study the phenomenological nature of the cycle-induced (centroid) eigenfrequencies. Our a…
Final Results from the Hubble Space Telescope Key Project to Measure the Hubble Constant
Kelson, Daniel D.; Illingworth, Garth D.; Huchra, John P. +12 more
We present here the final results of the Hubble Space Telescope (HST) Key Project to measure the Hubble constant. We summarize our method, the results, and the uncertainties, tabulate our revised distances, and give the implications of these results for cosmology. Our results are based on a Cepheid calibration of several secondary distance methods…
The European Photon Imaging Camera on XMM-Newton: The pn-CCD camera
Bignami, G. F.; Pietsch, W.; Haberl, F. +55 more
The European Photon Imaging Camera (EPIC) consortium has provided the focal plane instruments for the three X-ray mirror systems on XMM-Newton. Two cameras with a reflecting grating spectrometer in the optical path are equipped with MOS type CCDs as focal plane detectors (Turner \cite{mturner}), the telescope with the full photon flux operates the…