Search Publications
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-…
Search for short bursts of gamma-ray emission in spark chamber data: application to COS-B
Buccheri, R.; Maccarone, M. C.; Fry, W. F.
We describe an analysis method aimed to the detection of short (<1000 s) bursts in the emission of gamma-ray sources using spark chamber data. The method utilizes a maximum likelihood technique which looks for accumulations of photons, compatible with the point spread function of the experiment, within the whole observing time and the field-of-…
Intrinsic parameters of galactic luminous OB stars.
Butler, K.; Kudritzki, R. P.; Herrero, A. +3 more
We present the results of a spectroscopic analysis of 25 galactic luminous OB stars. The gravities are in general lower than previously assumed, especially for giants. The helium abundances are also higher than normal in many cases. Using data from the spectroscopic analysis, radii, luminosities and masses are derived. The observed wind terminal v…