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A Study of the Wavelength Calibration of NEWSIPS High-Dispersion Spectra
Smith, Myron A.
In this study we cross-correlate many IUE echellograms of a variety of well-observed stars to evaluate systematic error sources in the wavelength zero points (velocities) of all three cameras. We first evaluate differences between the final archived (``NEWSIPS'') and the originally processed (``IUESIPS'') echellograms. These show a marked time dep…
An astrophysical oscillator strength for the S ii 94.7-nm resonance line and S abundances in DLAs
Bonifacio, Piercarlo; Molaro, Paolo; Caffau, Elisabetta +2 more
By using UV spectra for the O star HD 93521 taken with the ORFEUS II echelle spectrograph, we determine an `astrophysical' f value for the Siiλ94.7-nm line: f=0.00498-0.00138+0.00172, error at 1σ level. This is almost a factor of 30 smaller than the guessed value found in the Kurucz data base (f=0.1472), which was until now the only one available …
Modulation Near Solar Maximum at High Solar Latitudes: Observations From the Ulysses Cospin High Energy Telescope
McKibben, R. B.; Zhang, M.; Lopate, C.
The three-dimensional structure of the solar maximum modulation of cosmic rays in the heliosphere can be studied for the first time by comparing observations from Ulysses at high solar latitudes to those from in-ecliptic spacecraft, such as IMP-8. Observations through mid-2000 show that changes in modulation remain well correlated at Earth and Uly…
New determination of the solar apex
Duflot, M.; Burnage, R.; Fehrenbach, Ch.
Many studies recently have been performed to determine the velocity vector of the Sun, mainly using the latest data on proper motions and parallaxes given by the Hipparcos satellite. We wished to carry out a similar study using totally independent data: the numerous radial velocities (RV) obtained with the Fehrenbach Objective Prisms (PO). This me…
The effect of anisotropic gas pressure on Alfvén-wave transmission and test-particle acceleration at parallel shock waves
Vainio, R.; Schlickeiser, R.
Alfvén-wave transmission through a parallel shock in case of an anisotropic gas pressure (Pparallel!=q Pperpendicular to is considered from the point of view of test particle acceleration in such shock waves. Treating the shock's gas compression ratio and the firehose factor, phi =1-4pi (Pparallel-Pperpendicul…
Cosmic Ray Isotopic Composition Studies with the Ulysses High Energy Telescope: Implications for Origin and Distribution in the Galaxy
Simpson, J. A.; Connell, J. J.
The isotopic abundances of the Galactic cosmic radiation measured in the Heliosphere provide unique information on acceleration, propagation modes and containment times in the Galactic magnetic fields. Nuclear interactions with interstellar matter lead to observable γ-radiation production and, thus, to direct information on cosmic ray distribution…
Research Note The evolutionary status of the early-type binary HD 115071
Stickland, D. J.; Lloyd, C.
An analysis of the Hipparcos photometry of HD 115071 shows that it is an ellipsoidal variable with a period of 2.73126 days, twice that suggested previously. Modelling the light curve combined with the available radial velocities suggests that the more massive, hotter component is smaller and less luminous than the cooler component, which is proba…
Revised Magnesium Abundances in Galactic Halo and Disk Stars
Mashonkina, L. I.; Shimanskaya, N. N.
A differential analysis of the magnesium abundances in 61 F-K dwarfs and subgiants with metallicities -2.6<[Fe/H]<+0.2 is performed based on published observational data. Fundamental parameters for 36 stars are determined: T eff from V-K and V-R; logg from HIPPARCOS parallaxes, and [Fe/H] and ξt from Fe II lines. The computations allow for n…
Properties of EUV and X-ray emission in solar active regions
Klimchuk, J. A.; Harra, L. K.; Matthews, S. A.
Using observations from the Coronal Diagnostic Spectrometer (CDS) on SoHO and the Soft X-ray Telescope (SXT) on Yohkoh we investigate how the spatial properties of active region emission observed in the EUV and X-ray range varies with temperature. We examine the contrast per unit area of the EUV emission from a number of active regions, and employ…
Analysis of a UV Event in a Polar Coronal Hole
Patsourakos, Spiros; Vial, Jean-Claude
We present observations of a UV event which occurred in a polar coronal hole. They were obtained by SUMER on SOHO in several chromospheric and transition region spectral lines. Its birth site was about 50 arc sec inside the limb and in a network lane showing a net outflow before its initiation. The event had an extension of about 5 arc sec along t…