Search Publications

Faint Stars and the Structure of the Galaxy

Wolf, C.; Meisenheimer, K.; Jahreiss, H. +2 more

Coronal Holes Versus Normal Quiet Sun Observed with SUMER

Solanki, S. K.; Wilhelm, K.; Brković, A. +5 more

We present a preliminary analysis of spectral lines obtained with the SUMER instrument (Solar Ultraviolet Measurements of Emitted Radiation) onboard the Solar and Heliospheric Observatory (SOHO), as observed during three observing campaigns. From the 70 observed spectral lines, we selected 12, representing 9 ions or atoms, in order to analyse line…

[Alii] in the ultraviolet spectrum of the symbiotic star RR Telescopii

Feibelman, W. A.; Mathioudakis, M.; Keenan, F. P. +4 more

An inspection of a GHRS/HST spectrum of the symbiotic star RR Telescopii reveals the presence of the [Alii] 3s^2 ^1S - 3s3p ^3P_2 line at a vacuum wavelength of 2661.06+/-0.08Å, 8.89+/-0.08Å away from the Alii] 3s^2 ^1S - 3s3p ^3P_1 intercombination transition at 2669.95Å, in good agreement with the theoretical prediction of Δλ=8.80Å. We also find…

Analysis of systematic errors of the photoelectric astrolabe catalog SIPA1

Lu, Chunlin; Xu, Jiayan; Li, Dongming +1 more

Systematic errors of the catalog obtained with the observation of Photoelectic Astrolabe Mark I (PHA I) of Shaanxi Astronomical Observatory, mounted at Irkutsk, Russia, are analyzed with reference to the Hipparcos catalog. It is shown that the systematic errors of the astrolabe catalog can be removed effectively using the Hipparcos Catalog as refe…

Ulysses HET Measurements of Electron-capture Secondary Isotopes: Testing the Role of Cosmic Ray Reacceleration

Simpson, J. A.; Connell, James J.

In recent publications, we have reported consistent cosmic ray Galactic confinement times from Ulysses HET measurements of 10Be, 26Al and 36Cl. The abundances of other secondary radio-isotopes, specifically electron-capture isotopes such as 49V and 51Cr, are a crucial test of cosmic ray reacceleration. Reacceleration is implicit in interstellar sh…

Sequences of Nearby Open Clusters with Hipparcos

Arenou, F.; Lebreton, Y.; Robichon, N.

Effects on UV lines observations of stationary plasma flows confined in coronal loops

Orlando, S.; Peres, G.

We describe a method which uses a rather detailed model of coronal loop hosting a siphon flow as a diagnostic tool to interpret solar UV and X-ray observations in selected bands and lines. We apply the method to investigate the deviations from ionization equilibrium induced by stationary plasma flows confined in coronal loops and their effects on …

UVCS Observations and Modeling of Streamers

Raymond, J. C.; van Ballegooijen, A. A.; Vásquez, A. M.

We present results derived from the analysis of an equatorial streamer structure as observed by the UVCS instrument aboard SOHO. From observations of the H I Lyα and Lyβ lines we infer the density and temperature of the plasma. We develop a preliminary axisymmetric, magnetostatic model of the corona which includes the effects of gas pressure gradi…

Photoelectric Vilnius Photometry of Hipparcos Turn-Off Region Stars

Ezhkova, O. V.; Lazauskaite, R.; Bartasiute, S.

Seven-color photometry in the Vilnius system and photometric classification in terms of spectral type, absolute magnitude and metallicity are presented for 145 Hipparcos stars of the turn-off region, most of which have parallaxes determined to an accuracy of at least 15%. The stars selected for the observing program included those identified kinem…

Loop Models from SOHO Observations

Landini, M.; Solanki, S.; Landi, E. +2 more

The Coronal Diagnostic Spectrometer (CDS) on SOHO is a grazing/normal incidence spectrograph, aimed to produce stigmatic spectra of selected regions of the solar surface in six spectral windows of the extreme ultraviolet from 150 Å to 785 Å (Harrison et al. 1995). In the present work, CDS, EIT, MDI and Yohkoh observations of active region lops hav…