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ISOPHOT Observations of Dust Disks around Main Sequence (Vega-Like) Stars
Walker, H. J.; Heinrichsen, I.
The photometer (ISOPHOT) on the Infrared Space Observatory (ISO) has proved to be invaluable for investigating the dust around main sequence stars (both prototypes and candidate Vega-like stars). The long wavelength camera (at 60 and 90 µm) has been used to map the area around the stars to establish whether the dust disk is extended. Low-res…
Microscale Structures on the Quiet Sun and Coronal Heating
Vial, J. -C.; Bocchialini, K.; Velli, M. +3 more
We present some results concerning transient brightenings on the quiet Sun, based on data from the Extreme-Ultraviolet Imaging Telescope on board the Solar and Heliospheric Observatory. Histograms of intensity are found to be well fitted by χ2 distributions for small values of the intensity, while at high intensities power-law distribut…
PG 2131+066: A Test of Pre-White Dwarf Asteroseismology
Reed, M. D.; Kawaler, Steven D.; O'Brien, M. Sean
PG 2131+066 is a composite-spectrum binary with a hot pulsating PG 1159-type pre-white dwarf and an early M-type main-sequence star. Analysis of Whole Earth Telescope observations of the pulsating pre-white dwarf component provided an asteroseismological determination of its mass, luminosity, and effective temperature. These determinations allowed…
The Near-Ultraviolet Continuum of Late-Type Stars
Lambert, David L.; Allende Prieto, Carlos
Analyses of the near-ultraviolet continuum of late-type stars have led to controversial results regarding the performance of state-of-the-art model atmospheres. The release of the homogeneous International Ultraviolet Explorer (IUE) final archive and the availability of the high-accuracy Hipparcos parallaxes provide an opportunity to revisit this …
Techniques for galactic dust measurements in the heliosphere
Krüger, Harald; Grün, Eberhard; Landgraf, Markus +5 more
Galactic interstellar dust (ISD) is the major ingredient in planetary formation. However, information on this important material has been extremely limited. Recently, the Ulysses dust detector has identified and measured interstellar dust outside 1.8 AU from the Sun at ecliptic latitudes above 50°. Inside this distance it could not reliably distin…
Pick-up Ion Measurements in the Heliosphere – A Review
Geiss, J.; Gloeckler, G.; von Steiger, R. +1 more
Measurements of the composition and spatial distribution of pick-up ions inside the heliosphere are reviewed. The first interstellar 4He+pick-up ions were detected with the SULEICA instrument on the AMPTE spacecraft near Earth's orbit. Most data on pick-up ions were taken in the solar-wind and suprathermal energy range of SWI…
Radio Emissions from the Planets and their Moons
Zarka, P.
We review the present observational knowledge of planetary non-thermal radio emissions (spectrum, emitted power, source location, beaming, modulations and frequency-time structures), emphasizing high-latitude, auroral and satellite- induced components at the outer planets. Important results have been obtained in the past few years from the observa…
Structure and evolution of low-mass Population II stars
D'Antona, F.; Montalbán, J.; Mazzitelli, I.
The focus of the present paper is on the detailed description of the internal structures of low mass, population II stars, to clarify some issues about these stellar models and, mainly, their present reliability for observational comparisons. We then explore 1) the role of the local convective model; 2) the differences between "grey" and "non grey…
The Surprising Emission Distribution within the Helix Nebula Cometary Knots
O'Dell, C. R.; Henney, W. J.; Burkert, A.
We compare the morphology of the cometary knots in the Helix Nebula in different emission lines using Hubble Space Telescope Wide Field Planetary Camera 2 and Space Telescope Imaging Spectrograph observations. We find that the [N II] 6658 Å line emission from the cometary heads is displaced with respect to Hα, peaking at a position that is closer …
Hubble Space Telescope Infrared Imaging Polarimetry of Centaurus A: Implications for the Unified Scheme and the Existence of a Misdirected BL Lacertae Nucleus
Marconi, Alessandro; Capetti, Alessandro; Hough, J. H. +6 more
We report results from the Hubble Space Telescope (HST)/near-infrared camera and multiobject spectrometer (NICMOS) 2 µm imaging polarimetry of the central region of Centaurus A. In the vicinity of the nucleus we observe a complex polarization structure, which we explain by a combination of scattering of nuclear light and dichroic polarizatio…