Search Publications
About the origin of extinction in the gravitational lens system MG J0414+0534
Magain, P.; Burud, I.; Rigaut, F. +3 more
Photometric measurements of the highly reddened gravitational mirage MG J0414+0534 have been carried out either by PSF subtraction or by applying accurate deconvolution algorithms to optical (R, I) and near-infrared (K) images obtained at CFHT and NOT under sub-arcsecond seeing conditions. It is confirmed that the close pair of images A1-A2 suffer…
Light perturbation from stellar nonradial oscillations: an application to solar oscillations
Provost, J.; Berthomieu, G.; Toutain, T.
We derive analytical expressions for the emerging intensity and flux perturbations due to stellar nonradial oscillations taking into account the sphericity of the emitting layers. These expressions are derived using both the Eulerian and Lagrangian formulations. We show, analytically and numerically, that these formulations are equivalent and that…
Coronal velocity measurements with Ulysses: multi-link correlation studies during two superior conjunctions
Pätzold, M.; Plettemeier, D.; Janardhan, P. +5 more
A well-known method for studying the solar wind very close to the Sun (heliocentric distances: 4 to 40 solar radii) is by radio sounding between a spacecraft at superior conjunction and the Earth. The Ulysses Solar Corona Experiment was performed at the spacecraft's two solar conjunctions in summer 1991 and winter 1995, during which dual-frequency…
Linear polarization and molecular filamentary clouds
Gahm, G. F.; Kaas, A. A.; Carlqvist, P. +1 more
We have carried out deep CCD polarimetry in the I band in selected fields in three filamentary, molecular clouds: the L1400 complex, L204, and MBM25, at galactic latitudes 4degr , 21degr , and 31degr , respectively. I magnitudes and the degree and direction of linear polarization were measured with satisfactory accuracies for 387 stars down to I=1…
Ion Temperatures as Observed in a Solar Coronal Hole
Wilhelm, K.; Tu, C. -Y.; Marsch, E.
From the widths of the extreme ultraviolet (EUV) lines measured by the SUMER instrument on SOHO, it was found previously (Tu et al. 1998) that the average temperature of Ne+7, at heights (relative to h0) above the southern solar limb from 17″ to 64″, ranges between 1.3 and 5 × 106 K and of Ne+6 between 1…
On the nature of the H BT I infrared emission lines of tau Scorpii
Waters, L. B. F. M.; de Koter, A.; Geballe, T. R. +4 more
We present Hα , He i lambda 2.058 mu m and 6 hydrogen Brackett and Pfund lines of tau Sco (B0.2V) obtained using the ground-based INT and UKIRT instruments as well as satellite data from ISO. The infrared lines all show core emission. We have investigated the formation of these lines using sophisticated non-LTE models. The observed emission in the…
Relationships among the Intensities of LI-, BE-, and NA-like Resonance Lines in Collisionally Ionized Astrophysical Plasmas (105<=Te<=107 K)
Feldman, U.; Laming, J. M.
The strongest lines emitted from optically thin collisionally ionized astrophysical plasmas are usually those of the Li-, Be-, and Na-like sequences. When numerous other weaker lines are also measurable in the spectrum, the derivation of relative element abundances is reasonably straightforward. However, for many sources only the strongest lines w…
Gamma Persei: a challenge for stellar evolution models
Pourbaix, D.
From the published visual and spectroscopic observations together with some unpublished radial velocities kindly provided by R.F. Griffin, we determine an orbit which accurately reproduces the time of the primary eclipse observed by \cite*{Griffin-1994} and also recompute Hipparcos astrometric parameters. The orbital parallax is slightly off with …
The density structure of a solar polar coronal hole
Warren, H. P.; Hassler, D. M.
Electron densities derived from Si III, Ne VII, Mg VIII, Si VIII, and Mg IX line ratios observed above the limb of a polar coronal hole with the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer on the Solar and Heliospheric Observatory (SoHO) are presented. The electron densities are consistent with a constant pressure of 1…
Hipparcos catalogue orientation as obtained from observations of minor planets
Chernetenko, Yu. A.; Batrakov, Yu. V.; Gorel, G. K. +1 more
Ground-based photographic observations of 12 minor planets obtained at Nikolaev observatory (Ukraine) between 1961-1995 were reduced to the Hipparcos catalogue system and processed by the least squares method (LSM) separately and in combination with the Hipparcos NDAC (the Northern Data Analysis Consortium) and FAST (the Fundamental Astronomy by S…