Search Publications
Radio emission from Jupiter observed by ULYSSES before and after encounter
Lecacheux, A.; Barrow, C. H.
The polarization and the occurrence probability of the radio emission from Jupiter at 940 and 52 kHz are compared before and after encounter. It is found that, after encounter, the right-hand polarized Main Component of the broad-band kilometric emission (bKOM) is not present while the left-hand polarized Intermittent Component is considerably enh…
Similarity of the variability patterns in the EXOSAT and GINGA folded light curves of the Seyfert galaxy NGC 6814.
Karas, V.; Abramowicz, M. A.; Bao, G. +1 more
The Seyfert galaxy NGC 6814 is known to show periodic variation of its X-ray luminosity. We found that the sequences of peaks (variability patterns) in the folded X-ray light curves constructed from the Exosat and Ginga data are remarkably similar when one ignores amplitudes of the peaks and considers only their phases. The stable pattern consists…
The Hyades distance and white dwarf constraints.
Weidemann, V.
It is demonstrated how recent determinations of surface gravity and gravitational red shifts for the Hyades white dwarfs constrain the distance of the cluster for which very discrepant values between trigonometric and kinematic results are presently discussed. If the surface gravity data are correct, the Hyades modulus must be close to m - M = 3.3…
Systematic deformations of the apparent almucantar as derived from Danjon astrolabes in Paris and Santiago de Chile
Pesek, I.; Vondrak, J.; Chollet, F. +1 more
Systematic deformations of apparent almucantar based on long series of observations with Danjon astrolabes in Paris and Santiago de Chile are derived. It is shown that their amplitudes of order of 0".1 - 0".2 have significant seasonal character. Comparison of the results based on two different catalogs (FK4 and FK5) make us believe that at least 5…
X-ray spectral variability of the Seyfert galaxy NGC 4593.
Ghosh, K. K.; Soundarajaperumal, S.
X-ray (0.1-10 keV) spectra of NGC 4593 were obtained with EXOSAT on seven epochs between 1984 and 1986 using the low and medium energy detectors. Detailed results of the spectral analysis of the seven spectra (obtained from the EXOSAT database) of this galaxy are presented here. Power-law, two power-law, thermal bremsstrahlung and broken power- la…
Simulated imaging of the upper atmosphere of active stars
Donati, J. -F.; Catala, C.
We have applied the principles of indirect stellar surface imaging (Doppler imaging) for simulated mapping of active regions in the upper atmosphere of cool active stars. Our tests illustrate how synthetic distributions at the chromosphere or transition region level can be recovered from time series of high resolution profiles of UV lines, as sate…
Evolution of SN 1987A in the ultraviolet.
Sanz Fernandez de Cordoba, L.
Two observational aspects of the evolution of SN 1987A in the UV are presented, based on IUE data. First, the spectral evolution of the NV, NIV], HeII, OIII], NIII] and CIII] emission lines in the period from March 13, 1987 to March 12, 1990. And secondly, the evolution of the SN 1987A continuum fluxes in various UV bands using SWP and LWP spectra…
A global analysis method for astrolabe observations
Chollet, F.
In a previous paper (Chollet & Najid 1992), we gave the general principles of a new global method to analyze the astrolabe observations. The fundamental equation was obtained from the classical one in which the corrections to the star positions at the observational epoch are replaced by developments that contain the corrections to the star pos…
Precise measurement of the right ascension of the Geminga pulsar using COS-B data.
Li, T. P.; Cheng, L. X.; Ma, Y. Q. +2 more
We have obtained a more precise value of the right ascension and a new spin evolution law of the Geminga pulsar using COS-B data on the assumption 0r high stability of the absolute phase. The new value is a(1950)=6h30m59s .057, with error about 0.5 arcsec, compared with the 3.2 arcsecs from the Einstein HRI result.…
The new Be-type star HD 147196 in the rho Ophiuchi dark cloud region.
Perez, M. R.; The, P. S.; de Winter, D. +1 more
The newly discovered hot-emission line star, HD 147196 in the Rho Oph dark cloud region was observed spectroscopically and photometrically and high and low resolution IUE spectra were obtained. The finding of Irvine (1990) that this relatively bright star show its H-alpha-line in emission is confirmed. Previous H-alpha-surveys of the Rho Oph star-…