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HIPPARCOS extragalactic link by means of absolute proper motions of stars related to galaxies: Kyiv solution.
Rybka, S. P.; Yatsenko, A. I.; Kharchenko, N. V. +1 more
Absolute proper motions of stars with respect to galaxies obtained within the KSZ and MEGA programmes were used in the determination of spin parameters of the Hipparcos catalogue system relative to the inertial reference frame. The Kyiv part of the Bonn-Potsdam-Kyiv project "Hipparcos extragalactic link by photographic astrometry" is discussed. So…
IUE observations of Beryllium II lines in Lithium-rich giant stars.
de Medeiros, J. R.; Monier, R.; Lebre, A. +1 more
IUE spectra of the Beryllium II region are presented for two Lithium-rich giant stars, HD 9746 and HD 112127. In either spectrum there is no sign of significant Beryllium features at the BeII lines 3130.416Å or 3131.064Å, which seems to indicate that Be was depleted in these two Lithium-rich giants. This suggests that some additional Lithium was p…
Refined analysis of interplanetary H-Lyα spectra obtained with the Hubble-Space Telescope GHRS spectrometer.
Clarke, J. T.; Scherer, H.; Fahr, H. J.
Here we present a new synoptic analysis of 5 HST-GHRS interplanetary H-Lyα spectra obtained at different lines of sight from different positions of the earth in its orbit. The spectral analysis aimed at the derivation of actual interstellar gas parameters is carried out on the basis of a newly developed Lyα radiation transport code taking into acc…
Asymmetric Hα disk emission dominates the HST/FOS spectrum of Circinus X-1.
Caraveo, P. A.; Bignami, G. F.; Mignani, R.
CircinusX-1 is an highly variable X/radio binary source showing regular flux modulations with a periodicity of ~16.6days, probably coincident with the orbital period of the binary system. Here we present HST/FOS spectra of the optical counterpart taken around the predicted X-ray maximum. Strong Hα in emission, itself accounting for almost 50% of t…
HST Data suggest proper motion for the optical counterpart of GRB 970228.
Caraveo, P. A.; Bignami, G. F.; Mignani, R. P. +1 more
After a quarter of a century of γ-ray burst (GRB) astronomy, the Italian-Dutch satellite BeppoSAX on Feb 28^th^, 1997 detected a soft X-ray afterglow from GRB 970228 and positioned it accurately. This made possible the successful detection of an optical transient. Two public Hubble Space Telescope (HST) images of the GRB/optical transient region w…
UV Observations of dwarf novae in quiescence - effects of evaporation?
Meyer, F.; Meyer-Hofmeister, E.; La Dous, C.
IUE spectra of dwarf novae in quiescence provide information on the inner part of the accretion disk. In the framework of the evaporation model the mass flow of about 10^-11^Msun_/yr is understood as accretion via a hot corona above the cool inert disk. The UV radiation originates from the transition region between disk and corona, and …
Photometry with a periodic grid. I. A new method to derive angular diameters and brightness distribution.
Mignard, F.; Hestroffer, D.
The interest of observations of point sources with a periodic grid has been recognized for long in astrometry because of the direct relation existing between the position in the sky and the phase of the modulated signal. We investigate in this paper a complementary aspect by showing how observations of an extended stellar or planetary object carri…
ORFEUS observations of SVI, OVI and PV in the stellar wind from the nucleus of NGC 6543.
Grewing, M.; Appenzeller, I.; Krautter, J. +9 more
During the ORFEUS-SPAS (Orbiting Retrievable Far and Extreme Ultraviolet Spectrometer on the Shuttle Pallet Satellite) mission STS-51, flown in September 1993, we observed, to our knowledge for the first time, the central star of the planetary nebula NGC 6543 in the far ultraviolet (90nm-115nm) wavelength region using the University of California,…
Understanding some moving groups in terms of a global spiral shock.
Figueras, F.; Torra, J.; Comeron, F.
We present a schematic model to interpret the kinematics of some major moving groups in the solar neighbourhood. The origin of these groups is assumed to lie in large scale spiral shocks which may be responsible for the spiral arms in the galactic disk, which provide the initial conditions in the velocities of stars formed as a consequence of them…
Optical emission in the radio lobes of Cygnus A.
Nilsson, K.; Jones, L. R.; Lehto, H. J. +2 more
Deep optical imaging and spectroscopy of stellar objects in the radio lobes of Cygnus A have been carried out. Brighter optical objects close to the radio hotspots are either confirmed or suspected Galactic stars. Very faint optical emission is found coinciding with hotspot D (R~23.1) and hotspot B (V~25.4). The implications of these observations …