Search Publications
HIPPARCOS photometry - FAST main mission reduction
Mignard, F.; Falin, J. L.; Froeschle, M.
In this paper we describe a photometric analysis of the Hipparcos data collected with the main detector. The overall principles of the photometric reduction are presented along with the first results. Both results at the transit level and over longer time scales are considered. We show that for a non-variable star of magnitude 8.5 an accuracy as g…
Applications of the infrared flux method to 3 cool AP stars (78 Virginis, 52 Herculis A and CS Virginis) and comparison of their energy distributions to model atmospheres.
Monier, R.
The infrared flux method proposed by Blackwell and Shallis (1977) is used, along with a comparison of the observed energy distribution to model grids, in order to determine the fundamental parameters of three cool Ap stars: 78 Vir, 52HerA, and CS Vir. The degree to which their energy distributions can be reproduced using currently available model …
28. Tycho transit detection.
Wagner, K.; Hog, E.; Wicenec, A. +3 more
By means of some extracted parts of the raw countrates of the Tycho photomultipliers the method of detecting signals of stars and estimating their amplitudes and transit positions is described. The elimination of disturbances due to spikes with the help of sophisticated folding and background determination methods is presented.
Expected accuracy of the 1900-1990 earth orientation parameters in the HIPPARCOS reference frame
Vondrak, Jan; Feissel, Martine; Essaifi, Najat
Based on the space and time distribution of observations available over 1900-1990 for estimating the motion of the earth rotation axis in space and relative to the earth's crust, and universal time, we evaluate the accuracy of the earth orientation parameters in the framework of their global analysis in the Hipparcos reference frame currently unde…
Photospheric velocity gradients in B1 supergiants.
Massa, D.; Shore, S. N.; Wynne, D.
We present IUE spectra for a set of B1 supergiants. These data clearly demonstrate that the Si III 1300A multiplet (lower level 6.6 ev above ground) becomes progressively more asymmetric with increasing luminosity or, equivalently, mass loss. In the most luminous supergiants, the cores of the 1300A multiplets become displaced by up to -150 km/s re…
Computation of ephemerides for long-period variable stars for the HIPPARCOS mission
Figueras, F.; Barthes, D.; Mennessier, M. O. +2 more
In order to predict the luminosities of LPVs observed by Hipparcos, many visual light curves, characterized by irregularly spaced data, were analyzed using original and complementary methods. The obtained power spectra, including amplitudes and phases, are utilized in the computation of the ephemerides. The predictions are regularly checked with o…
TYCHO photometry calibration and first results
Snijders, M. A. J.; Grewing, M.; Lindegren, L. +6 more
A description of the data reduction methods used for the Tycho photometry and the software package to implement these methods is presented. Results derived from a preliminary reduction of eight weeks of data employing these methods are reported. A critical discussion of the sources of photometric errors and the expected and achieved photometric ac…
Early improvements to the HIPPARCOS Input Catalogue through the accumulation of data from the satellite - Including the NDAC attitude reconstruction description
van Leeuwen, Floor; Lindegren, Lennart; Penston, Margaret J. +2 more
A description of ways in which the Northern Data Analysis Consortium (NDAC) accumulates positional and photometric data as obtained in the early stages of the reduction of data from the Hipparcos instrument is presented. An outline of the closely associated attitude reconstruction process is also given. Positional internal accuracies in arcsec, an…
The Cramer-Rao lower bound and stellar photometry with aberrated HST images
Jakobsen, P.; Greenfield, P.; Jedrzejewski, R.
The Cramer-Rao lower bound theorem of statistics is applied to the problem of extracting 2D stellar photometry from aberrated Hubble Space Telescope camera images. The theorem is used to derive a simple and general expression for the best possible photometric precision that can be derived from a given image, regardless of what image processing or …
Cool star flux spectra for population studies in galaxies.
Parthasarathy, M.; Morossi, C.; Malagnini, M. L. +1 more
Five solar-composition cool giant stars have been observed with the IUE low resolution mode. The UV energy distributions were merged with visual spectrophotometry from the literature and compared with predictions from two new grids of model atmospheres. Atmospheric parameters were derived consistent with the literature data by matching observation…