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Bubbles, Bow-Shocks, and Bullets over Broad-lines: Three Ionized Outflows Resolved with HST
Veilleux, S.; Ferruit, P.; Cecil, G.
HST images and spectra of high-velocity outflows from three AGN: (1) Show 5 arcsec -long bow shock/Mach disk complexes at the ends of the active radio jet in NGC 4258. We argue that the jet has precessed to its current orientation seen at VLBI-scales. (2) Fully resolve [O III]5007Å and H beta line profiles in the NLR of NGC 1068, and show compact …
The Spectrum and Term System of S VII
Jupén, Christer; Engström, Lars
The spectrum of six times ionized sulphur, S VII, has been investigated in the wavelength region 200-4000Å by means of the beam-foil and laser-produced plasma techniques. The analysis comprises 219 lines of which 105 are newly identified. The present work establishes 123 2s22p5nl energy levels of which 66 are new. The level energies are determined…
Motion of auroral ion outflow structures observed with CLUSTER and IMAGE FUV
Lundin, R.; Winningham, J. D.; Dandouras, I. +22 more
During February 2001 the CLUSTER satellites recorded a number of perigee passes through the midnight auroral zone. We concentrate on one pass, on 23 February 2001, when structured outflow was observed. Simultaneous observations of the aurora were available from the FUV instrument on IMAGE. The features in the ion outflow observed by the Cluster Io…
Quantitative Stellar Spectral Classification. II. Early Type Stars
García, J.; Stock, J.; Stock, M. J. +1 more
The method developed by Stock & Stock (1999) for stars of spectral types A to K to derive absolute magnitudes and intrinsic colors from the equivalent widths of absorption lines in stellar spectra is extended to B-type stars. Spectra of this type of stars for which the Hipparcos catalogue gives parallaxes with an error of less than 20% were ob…
The rising phase of solar cycle 23 as seen by Ulysses
Marsden, R. G.
Following its highly successful survey of the latitudinal structure of the heliosphere under near-minimum solar activity conditions, the Ulysses space-probe embarked in 1998 on a second out-of-ecliptic orbit of the Sun. This second high-latitude survey will culminate near solar maximum, offering a unique opportunity to study the polar regions of t…
A discussion of recent evidence for solar irradiance variability and climate
Kuhn, Jeff; Fröhlich, Claus; Sofia, Sabatino +2 more
One of the over-arching questions, among others, to be addressed by studying Sun-Earth connections is: "Is the climate changing in a way we can understand and predict?" The Earth's climate is the result of a complex and incompletely understood system of external inputs and interacting parts. Climate change can occur over a range of time scales, ma…
The acceleration and release of solar energetic particles in events from April 20 - May 9, 1998
Simnett, G. M.
The most active period in X-rays of the current solar cycle to date (August 1998) occurred from April 23 - May 9, 1998, when there were four X-class flares and two more which exceeded M6. All were likely to have been from AR 8210 (two were occulted and thus didn't have positive identification, although the coronal Yohkoh images were consistent wit…
Do red giant stars pulsate in high overtones?
Percy, John R.; Hosick, JoAnne
About 30 photometrically variable red giant stars have periods less than 10d, as determined by the compilers of the Hipparcos Catalogue from Hipparcos photometric measurements. These periods, when combined with estimates of the radii and masses of these stars, and with pulsation theory, imply that these stars are pulsating in very high overtones. …
A study of opacity in SOHO-SUMER and SOHO-CDS spectral observations. III. The validity of the escape probability model
Fischbacher, G. A.; Loch, S. D.; Summers, H. P.
The assumptions underpinning escape probability and absorption factor methods for describing spectral emission from optically thick plasmas, are addressed to test the range of validity of the associated expressions and to develop them for use within non-stratified atmospheres which include plasma flow and line blending. It is found that for modera…
Astrophysics in 2001
Aschwanden, Markus J.; Trimble, Virginia
During the year, astronomers provided explanations for solar topics ranging from the multiple personality disorder of neutrinos to cannibalism of CMEs (coronal mass ejections) and extra-solar topics including quivering stars, out-of-phase gaseous media, black holes of all sizes (too large, too small, and too medium), and the existence of the unive…