Search Publications
Modulation of Galactic Cosmic Rays at Solar Minimum
Heber, B.; Burger, R. A.
Cosmic ray particles respond to the heliospheric magnetic field in the expanding solar wind and its turbulence and therefore provide a unique probe for conditions in the changing heliosphere. During the last four years, concentrated around the solar minimum period of solar cycle 22, the exploration of the solar polar regions by the joint ESA/NASA …
The Effect of Abundance Variations on Estimates of the Densities of Broad-Line Region Clouds in Quasars
Gaskell, C. Martin; Snedden, Stephanie A.
There has been a long-standing discrepancy between the densities deduced from studies of the variability of quasar emission lines and those inferred from standard photoionization analyses. We have found that the higher metal abundances now believed to be present in most quasars lead to the higher densities being predicted by photoionization models…
Mid-infrared spectral images of planetary nebulae with ISOCAM
Rouan, D.; Siebenmorgen, R.; Cesarsky, D. +5 more
This paper presents the results of ISOCAM-CFV spectral images between 5 and 16.5 mu m of the planetary nebulae, NGC 6543, NGC 7027, NGC 6302, NGC 6720, BD+30degr 3639, VY 2-2, and of the proto-planetary nebula CRL2688. All the nebulae, except VY 2-2 are spatially resolved in the continuum and in the different spectral features. Integrated CVF spec…
Spectroscopic Constraints on Models of Ion-cyclotron Resonance Heating in the Polar Solar Corona
Cranmer, S. R.; Kohl, J. L.; Field, G. B.
Using empirical velocity distributions derived from UVCS and SUMER ultraviolet spectroscopy, we construct theoretical models of anisotropic ion temperatures in the polar solar corona. The primary energy deposition mechanism we investigate is the dissipation of high frequency (10-10000 Hz) ion-cyclotron resonant Alfvén waves which can heat and acce…
Discrete cloud activity in Saturn's equator during 1995, 1996 and 1997
Rojas, J. F.; Colas, F.; Lecacheux, J. +2 more
A regular extensive CCD imaging of Saturn allowed us to analyze the discrete cloud activity in the Equatorial Zone from 1995 to 1997. The large-scale storm observed in 1994 at +10° ( Sanchez-Lavega et al., 1994, 1996) was rediscovered in 1995, reaching a lifetime >1 year. Its slow motion characterized by a zonal velocity difference of -150 ms <…
Resonance Scattering of 30.4 NM Chromospheric Radiation by Coronal Singly Ionized Helium Observed with EIT
Delaboudinière, J. P.
A diffuse emission is observed above the solar limb in the `304 Å' channel of the Extreme-Ultraviolet Imaging Telescope (EIT) onboard the SOHO spacecraft. Part of this emission is attributed to the presence of residual singly-ionized helium in the solar corona, which resonantly scatters the intense helium `Lyman alpha' radiation of the chromospher…
Telescopic Observations of Mars, 1996-1997: Results of the Marswatch Program
Parker, D. C.; Beish, J. D.; Troiani, D. M. +2 more
During the 1996-1997 apparition of Mars, Marswatch and the International Mars Patrol (IMP) of the Mars Section of the Association of Lunar and Planetary Observers (ALPO) received 2750 observations from 70 observers in 14 countries. Approximately 40% of these observations are CCD images, many of which were obtained through filters covering a spectr…
Toward an Orbit for the High-Luminosity Cepheid T Monocerotis
Evans, Nancy Remage; Wahlgren, Glenn M.; Carpenter, Kenneth +4 more
We have obtained new velocities of the long-period Cepheid T Mon from the ground and velocities of its hot companion with the Hubble Space Telescope (HST) and the International Ultraviolet Explorer (IUE). Although observations do not cover a full orbit, both the maximum and minimum orbital velocities have now been obtained. We present a preliminar…
Observations of Jovian upstream events by Ulysses
Armstrong, T. P.; Haggerty, Dennis
The heliosphere instrument for spectra composition and anisotropy at low energy (HISCALE) experiment on board the Ulysses spacecraft, during the Jovian flyby, measured 192 distinct 61-77 keV upstream ion events of probable Jovian origin. Event-averaged characteristics such as intensities, anisotropies, power law spectral exponents, averaged event …
Discovery of pulsations in the AM star HD 13079
Leone, F.; Sagar, R.; Kurtz, D. W. +8 more
Pulsation in cool main-sequence Am stars is a rare phenomenon observed in a few marginal Am stars and only one classical Am star. The chemically peculiar star HD 13079 is shown to be pulsating with a 78-min period and a peak-to-peak B amplitude of 0.02mag. The Hipparcos parallax, uvbyβ photometry and pulsations together suggest that HD 13079 is an…