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First Results from SWAN Lyman α solar wind mapper on SOHO
Schmidt, W.; Bertaux, J. L.; Lallement, R. +7 more
After one year of almost flawless operation on board the SOHO spacecraft poised at L1 Lagrange point, we report the main features of SWAN observations. SWAN is mainly dedicated to the monitoring of the latitude distribution of the solar wind by the Lα method. Maps of sky Lα emissions were recorded througout the year. The region of maximum emission…
The Electron Drift Instrument for Cluster
Simpson, D.; Baumjohann, W.; Torbert, R. B. +20 more
Kinematic ages of OB associations
Brown, A. G. A.; de Zeeuw, P. T.; Dekker, G.
Astrometric data from the HIPPARCOS mission include measurements of early-type stars in nearly all OB associations within 1kpc from the Sun, and are available as of 1996. In anticipation thereof we studied the determination of kinematic ages and initial sizes of OB associations. These studies have traditionally been done using proper motion data. …
Active Regions Observed in Extreme Ultraviolet Light by the Coronal Diagnostic Spectrometer on SOHO
Young, P. R.; Mason, H. E.; Harrison, R. A. +4 more
We present observations of five active regions made by the Coronal Diagnostic Spectrometer (CDS) on the Solar and Heliospheric Observatory (SOHO). CDS observes the Sun in the extreme ultraviolet range 150-780 Å. Examples of active region loops seen in spectral lines emitted at various temperatures are shown. Several classes of loops are identified…
Astrometric Detection of a Low-Mass Companion Orbiting the Star AB Doradus
White, G. L.; Arenou, F.; Lindegren, L. +19 more
We report submilliarcsecond-precise astrometric measurements for the late-type star AB Doradus via a combination of VLBI (very long baseline interferometry) and HIPPARCOS data. Our astrometric analysis results in the precise determination of the kinematics of this star, which reveals an orbital motion readily explained as caused by gravitational i…
Solar Wind and Chromospheric Network
Tu, C. -Y.; Marsch, E.
A physical model of the transition region, including upflow of the plasma in magnetic field funnels that are open to the overlying corona, is presented. A numerical study of the effects of Alfvén waves on the heating and acceleration of the nascent solar wind originating in the chromospheric network is carried out within the framework of a two-flu…
Fundamental Stellar Parameters of γ2 Velorum from HIPPARCOS Data
Schaerer, Daniel; Schmutz, Werner; Grenon, Michel
We report parallax measurements by the HIPPARCOS satellite of γ2 Velorum and a few related objects. The distance of γ2 Vel is d = 258+41-31 pc, significantly smaller than the commonly adopted value to Vela OB2. For ζ Puppis d = 429+120-77 pc is in agreement with the canonical distan…
The distinction between OIafpe and WNLha stars. A spectral analysis of HD 151804, HD 152408 and HDE 313846.
Crowther, P. A.; Bohannan, B.
From detailed atmospheric analysis of the Galactic late O supergiants, HD 151804 (O8Iaf) and HD 152408 (O8:Iafpe) and the morphologically related Wolf-Rayet star, HDE 313846 (WR108; WN9ha) we conclude that little distinguishes the overall structure and composition of the stellar atmosphere of HD 152408 from HDE 313846, such that HD 152408 could be…
Observations of Polar Plumes with the SUMER Instrument on SOHO
Wilhelm, K.; Schühle, U.; Lemaire, P. +1 more
We present new observations of O vi 1032 Å line profiles in polar plumes, and inter-plume regions, on the disk and above the limb in the north coronal hole obtained with the SUMER (Solar Ultraviolet Measurements of Emitted Radiation) instrument on the SOHO (Solar and Heliospheric Observatory) spacecraft. On 22 May 1996, a 5 x 5 arc min spectroheli…
Double star data in the HIPPARCOS Catalogue
Badiali, M.; Pannunzio, R.; Arenou, F. +12 more
The Hipparcos Catalogue contains astrometric results for 117955 catalogue entries, many of which are in reality double or multiple stars. For 17917 entries special solutions were made in order to cope with the various manifestations of multiplicity, and 6763 other entries were flagged as suspected binaries but solved as single stars. Details of th…