Search Publications
Scattering of interplanetary radio waves at kilometric wavelengths
MacDowall, Robert J.; Hess, Roger A.
We report on measurements of the angular size of Jovian radio sources measured by the URAP instrument on the Ulysses spacecraft. The angular size is found to be substantially larger than that expected from the geometric size of the source, which is essentially a point source when viewed from Ulysses. This increase in size is due to scattering of t…
Reduction of the binary stars Δm measurements, obtained with the speckle interferometer of BTA of SAO RAS, into the standard photometric system
Zhuchkov, R. Ya.
For magnitude difference, measured with the speckle interferometer of the 6m telescope of SAO RAS, corrections for transformation from interferometer's photometric system into standard Johnson-Cousins V R I bands are calculated. The reduction accuracy is 0.01m - 0.02m. To determine the correction one has to know the magnitude…
The Structure of Proper-Motion Diagrams for Nearby Stars
Vereshchagin, S. V.; Reva, V. G.; Chupina, N. V.
The structure of the proper-motion diagrams for an ensemble of nearby field stars is analyzed using a simple model. For comparison, the observed proper-motion diagram is constructed using data of the Hipparcos catalog. A complete description is given of the modification of the van Altena method, which allows stars with similar space motions to be …
A comparative estimation of the accuracy of modern astrometric catalogues
Nefedjev, Yu. A.; Rizvanov, N. G.; Shaimukhametov, R. R.
A method for a comparative estimation of the accuracy of astrometric catalogues in the random meaning is offered. The estimation is done by comparison of star coordinates in the catalogues under study with star coordinates in the HIPPARCOS catalogues for various epochs. Variances of star positions and proper motions in the catalogues under investi…
A survey searching for the epoch of assembling of Hubble types
Pasquali, Anna; de Mello, DuÍlia F.
We have started a survey of galaxies at intermediate redshifts using the HST-STIS parallel fields. Our main goal is to analyse the morphology of faint galaxies in order to estimate the epoch of formation of the Hubble classification sequence. The high resolution of STIS images (0.05″) is ideal for this work and enables us to perform a morphologica…
ESA INTEGRAL and Cataclysmic Variables
Hudec, R.; Hroch, F.; Strobl, J. +1 more
Analysis of a coronal loop on the limb
Martens, P. C. H.; Cirtain, J. W.; Winter, H. D.
The ability to accurately measure the temperature and density of the solar atmosphere is essential to understanding the physical nature of Coronal loops. After data has been corrected to account for cosmic ray incidents on the CCD and instrumental effects, there are additional sources of error that must also be addressed. We applied a correction t…
Temporal variability of Mrk 421 from XMM-Newton observations
Haberl, F.; Papadakis, I.; Brinkmann, W. +1 more
Mrk 421 has been observed several times as a calibration target for the instruments on board XMM-Newton. We have studied in some detail the temporal and spectral variability of the source during eight pointings, mainly from the PN camera, which provides the by far highest S/N data available for that source.
Variations of the magnetic fields in large solar flares
Donea, A. -C.; Schunker, H.
We present preliminary results from high resolution observations obtained with the Michelson Doppler Imager (MDI) instrument on the SOHO of two large solar flares of 14 July 2000 and 24 November 2000. We show that rapid variations of the line-of-sight magnetic field occured on a time scale of a few minutes during the flare explosions. The reversib…
Conditional Statistics of Magnetic Turbulence and the Lateral Transport of Solar Energetic Particles
Matthaeus, W. H.; Ruffolo, D.; Chuychai, Piyanate
The transport of energetic particles perpendicular to the mean magnetic field in space plasmas long has been viewed as a diffusive process. However, there is an apparent conflict between recent observations of solar energetic particles (SEP): 1) SEP from impulsive solar flares can exhibit "drop outs" in which the intensity near Earth repeatedly di…