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Flow in streamer boundaries, and streamer stability
Suess, S. T.; Nerney, S.
Streamers can extend to many solar radii but the closed field regions, or helmets, reach no higher than 2-4 solar radii. The brightness boundary defining streamers is therefore, a boundary between different flow regimes rather than between static plasma and expanding solar wind. It is reasonable to assume that, this boundary divides fast coronal h…
Cosmic Helium Production
Flynn, Chris
K-dwarfs are very long lived, slowly evolving stars, so that their present day helium Y and metal content (metallicity Z) is essentially the same as when they were born. K-dwarfs thus contain a fossil record of the amount of helium and metals which has been produced in successive stellar generations over the lifetime of the Galaxy. We here estimat…
Proper Motion Objects in the Hubble Deep Field
Winget, D. E.; von Hippel, Ted; Mendez, R. A. +1 more
Using the deepest and finest resolution images of the universe acquired with the Hubble Space Telescope and a similar image taken 7 yr later for the Great Observatories Origins Deep Survey, we have derived proper motions for the point sources in the Hubble Deep Field-North. Two faint blue objects, HDF 2234 and HDF 3072, are found to display signif…
Far-Ultraviolet Spectroscopy of Star-forming Regions in Nearby Galaxies: Stellar Populations and Abundance Indicators
Keel, William C.; Holberg, Jay B.; Treuthardt, Patrick M.
We present Far Ultraviolet Spectroscopic Explorer spectroscopy and supporting data for star-forming regions in nearby galaxies, to examine their massive-star content and explore the use of abundance and population indicators in this spectral range for high-redshift galaxies. New far-ultraviolet spectra are shown for four bright H II regions in M33…
Prelaunch performance evaluation of the cometary experiment MUPUS-TP
Kührt, E.; Knollenberg, J.; Spohn, T. +13 more
This paper discusses test results obtained in both laboratory and terrestrial environment conditions for the ``Multipurpose Sensors for Surface and Sub-Surface Science'' Thermal Probe (MUPUS-TP), which has been developed for the European Space Agency Rosetta cometary rendezvous mission. The probe is intended to provide in situ long-term observatio…
A stratospheric balloon experiment to test the Huygens atmospheric structure instrument (HASI)
Patel, M. R.; Fulchignoni, M.; Hathi, B. +15 more
We developed a series of balloon experiments parachuting a 1:1 scale mock-up of the Huygens probe from an altitude just over 30 km to simulate at planetary scale the final part of the descent of the probe through Titan's lower atmosphere. The terrestrial atmosphere represents a natural laboratory where most of the physical parameters meet quite we…
Modulation in the solar irradiance due to surface magnetism during cycles 21, 22 and 23
Jain, K.; Hasan, S. S.
Magnetic field indices derived from synoptic magnetograms of the Mt. Wilson Observatory, i.e. Magnetic Plage Strength Index (MPSI) and Mt. Wilson Sunspot Index (MWSI), are used to study the effects of surface magnetism on total solar irradiance variability during solar cycles 21, 22 and 23. We find that most of the solar cycle variation in the tot…
XMM-Newton spectra of hard spectrum Rosat AGN: X-ray absorption and optical reddening
Page, M. J.; Carrera, F. J.; Mittaz, J. P. D.
We present the XMM-Newton spectra of three low-redshift intermediate Seyferts (one Sy 1.5, and two Sy 1.8), from our survey of hard spectrum Rosat sources. The three AGN are well fitted by absorbed powerlaws, with intrinsic nuclear photoelectric absorption from column densities between 1.3 and 4.0 × 1021 cm-2. In the brightes…
INTEGRAL observation of 3EG J1736-2908
Gehrels, N.; Grandi, P.; Chaty, S. +10 more
The possible identification by INTEGRAL of the EGRET source 3EG J1736-2908 with the active galactic nucleus GRS 1734-292 is discussed. The latter was discovered in 1990 and later identified with a Seyfert 1 galaxy. At the time of the compilation of the 3rd EGRET Catalog, it was not considered as a possible counterpart of the source 3EG J1736-2908,…
Scientific objectives and selection of targets for the SMART-1 Infrared Spectrometer (SIR)
Keller, H. U.; Hiesinger, H.; Mall, U. +3 more
The European SMART-1 mission to the Moon, primarily a testbed for innovative technologies, was launched in September 2003 and will reach the Moon in 2005. On board are several scientific instruments, including the point-spectrometer SMART-1 Infrared Spectrometer (SIR). Taking into account the capabilities of the SMART-1 mission and the SIR instrum…