Search Publications
Near-ultraviolet imaging of Jupiter's satellite Io with the Hubble Space Telescope
Boksenberg, A.; Barbieri, C.; Sartoretti, P. +7 more
The surface of Jupiter's Galilean satellite Io has been resolved for the first time in the near ultraviolet at 2850 A by the Faint Object Camera (FOC) on the Hubble Space Telescope (HST). The restored images reveal significant surface structure down to the resolution limit of the optical system corresponding to approximately 250 km at the sub-eart…
The energy distribution of 21 Comae Berenices (A3p): comparison to standard stars of similar spectral types and modeling.
Monier, R.; Megessier, C.
The energy distribution (ED) of 21 Com is constructed from 1200 to 22000 Å using UV and optical spectrophotometry and recent IR photometry (Fernley 1990). The comparison of the ED with those of standard A3 stars confirms the A3 spectral type ascribed to 21 Com by Cowley et al. (1969) and reveals many similarities with the A3 IV standard τ Vir. The…
Possible detection of Lyman alpha emission in the A7 III star gamma Bootis
Freire Ferrero, R.; Catalano, S.; Gouttebroze, P. +1 more
We analyze the archive high dispersion IUE spectrum SWP 10885 of Gamma Boo (A7 III) in the Ly-alpha region, using our own software. A faint stellar emission overlayed by a saturated interstellar absorption is detected. This result and the previous detection of Ly-alpha emission in Altair and Alpha Cep do suggest that the presence of chromospheric …
TYCHO Astrometry Calibration
Pedersen, H.; Lindegren, L.; Bastian, U. +6 more
The Hipparcos satellite's star mapper gives photon counts in two spectral channels simultaneously. The transit times and the signal amplitudes for each star across two groups of four slits are derived and used for astrometry and photometry, respectively, and this constitutes the Tycho project. The present paper describes the Tycho astrometric data…
First X-ray spectrum of the most luminous quasar PKS 2126-158.
Ghosh, K. K.; Soundararajaperumal, S.
For the first time the detailed results of the spectral analysis of the X-ray (0.1-10 keV) spectrum of the luminous (z = 3.27), radio-loud quasar, PKS 2126 - 158, are presented. The spectrum of this quasar was obtained from the EXOSAT database. Power law and fixed absorption model fits well with the spectrum. The parameters of this model suggest t…
The Spacelab-1 very wide field survey of UV-excess objects. III. Analysis of the IUE high-resolution spectra of two very hot sdO stars.
Deleuil, M.; Viton, M.
The IUE high resolution spectra of CPD-71 deg 172B had LSII+18 deg 9 (two subdwarfs with T(eff) = 60,000 K) are compared through a differential curve of growth technique. About 300 lines belonging to 15 ions have been identified in a series of selected windows, representing a global spectral domain of 50 A. Unknown lines account for 37 to 80 perce…
Method of comparison between determinations of the HIPPARCOS attitude
Donati, F.; Sechi, G.
An attitude comparison method for assessing the quality of the attitude estimates obtained by the Hipparcos data reduction consortia (FAST and NDAC) is presented. The method is illustrated by results obtained in a typical FAST-NDAC comparison developed during the attitude determination assessment phase. The aim of the attitude comparison is, initi…
Almucantar deformations in the method of equal altitudes
Pesek, I.
Systematic deformations of apparent almucantar of order of 0.1 arcsec were derived from two five-year series of circumzenithal observations by the method of equal altitudes. Simple method is presented which makes it possible to check for almucantar deformation all data obtained by the method of equal altitudes, selected for rereducing earth rotati…
UV observations of LB 3193 and LB 3116 : two hot post-AGB object in the galactic halo ?
Lamers, H. J. G. L. M.; Quin, D. A.
LB 3193 and LB 3116 have visual spectra indicating that they are B2-B5 supergiants situated at large distances from the galactic plane. UV observations of both objects show that they are metal deficient stars, whose energy distributions match their adopted atmospheric parameters. Further investigation of mass luminosity relationships of various ev…
EXOSAT measurement of the spectrum of Markarian 382.
Singh, K. P.; Rao, A. R.; Vahia, M. N.
The 0.1-10 keV X-ray spectrum of a Seyfert galaxy known as Markarian 382 (Mkn 382) is presented based on observations with the EXOSAT. The energy index (α) for the power-law X-ray continuum of Mkn 382 is measured to be 1.2^+0.16^_0.14_ which is higher than the canonical value found for the Seyfert galaxies. There is no evidence for intrinsic absor…