Search Publications
Deduced spectrum of interacting protons accelerated after the impulsive phase of the 15 June 1991 solar flare
Kocharov, L.; Rank, G.; Nieminen, P. +6 more
In June 1991 the Sun produced a famous series of six powerful flares. For the solar eruption on 15 June 1991 there exists a rich set of measurements, including in particular >~mma-ray and neutron observations of the COMPTEL instrument on board the COMPTON Gamma Ray Observatory (CGRO) satellite. The >~mma-ray and neutron emissions indicate pr…
HIPPARCOS positioning of Geminga: how and why
Caraveo, P. A.; Bignami, G. F.; Makarov, V. V. +4 more
Accuracy in the absolute position in the sky is one of the limiting factors for pulsar timing, and timing parameters have a direct impact on the understanding of the physics of Isolated Neutron Stars (INS). We report here on a high-accuracy measurement of the optical position of Geminga (mv=25.5), the only known radio-quiet INS. The pro…
Latitudinal Variation of Solar Subsurface Rotation Inferred from p-Mode Frequency Splittings Measured with SOI-MDI and GONG
Kosovichev, A. G.; Birch, A. C.
Analysis of p-mode frequency splittings as measured by the Solar Oscillations Investigation-Michelson Doppler Imager (SOI-MDI) on board the Solar and Heliospheric Observatory and the ground-based Global Oscillations Network Group (GONG) experiment reveal that the symmetric component of the solar rotation rate in the upper 4% by radius and closer t…
The D/H ratio at z=0.7 toward Q 1718+4807
Takahara, Fumio; Levshakov, Sergei A.; Kegel, Wilhelm H.
The apparent discrepancy between low and high D abundances derived from QSO spectra may be caused by spatial correlations in the stochastic velocity field. If one accounts for such correlations, one finds good agreement between different observations and the theoretical predictions for standard big bang nucleosynthesis (SBBN). In particular, we sh…
The Cosmic-Ray Radioactive Nuclide 36Cl and Its Propagation in the Galaxy
Simpson, J. A.; Connell, J. J.; DuVernois, M. A.
Radioactive 36Cl has been resolved from 35Cl and 37Cl for the first time in the cosmic radiation with measurements obtained from the high-resolution High-Energy Telescope (HET) carried on the NASA-ESA Ulysses spacecraft. Within the framework of a homogeneous propagation model wherein all 36Cl is of spall…
Wind Velocity Variations in the Luminous Blue Variable-Type Erupting Star of the Wolf-Rayet Binary HD 5980
Koenigsberger, G.; Auer, L. H.; Georgiev, L. +1 more
We present the wind velocity and UV luminosity variations in the Wolf-Rayet system HD 5980 obtained over a time span during which one of the stars of the system was transformed into a luminous blue variable and underwent an eruption. We are able to separate the velocity components of the two stars in the system: a stable velocity component at -170…
Very cold dust in the peculiar dwarf elliptical galaxy NGC 205
Haas, Martin
ISO observations of NGC 205 between 120 and 200 mu m resolve the emission from 20-24 K cold dust. It is extended to about 7farcm 5x7farcm 5 with bright concentrations in a 1farcm 5 north-south elongated area, similar to the that seen in HI. Supplemented by IRAS and mm literature data, the photometry of the total galaxy and the central region is di…
A comparison of HIPPARCOS parallaxes with planetary nebulae spectroscopic distances
Pottasch, S. R.; Acker, A.
The Hipparcos satellite has measured the parallax of a small sample of planetary nebulae. In this paper we consider the results for 3 planetary nebulae (PN) for which spectroscopic distances have also been determined from stellar gravities. These gravities in turn have been derived from profile fitting of selected hydrogen and helium lines (Mendez…
Discovery of a New Quadruple Lens HST 1411+5211
Barrientos, L. Felipe; Fischer, Philippe; Schade, David
Gravitational lensing is an important tool for probing the mass distribution of galaxies. In this Letter, we report the discovery of a new quadruple lens HST 1411+5211 found in archived Wide-Field Planetary Camera 2 images of the galaxy cluster CL 140933+5226. If the galaxy is a cluster member, then its redshift is z=0.46. The images of the source…
Late-type dwarf galaxies in the Virgo cluster - I. The samples
Brosch, Noah; Almoznino, Elchanan
We selected samples of late-type dwarf galaxies in the Virgo cluster with HI information. The galaxies were observed at the Wise Observatory using several broad-band and Hα bandpasses. UV measurements were carried out with the IUE Observatory from VILSPA, and with the FAUST shuttle-borne UV telescope. We describe the observations in detail, paying…