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Detection of short-term variations in Mira-type variables from HIPPARCOS photometry
de Laverny, P.; Mignard, F.; Mennessier, M. O. +1 more
The Hipparcos photometric observations carried out over 37 months have been investigated in detail for ~ 250 Miras. This leads to an unexpected by-product of the mission that we already suspected from ESOC real-time reductions: the first detection from space of photometric short-term brightness variations in Mira-type variables. Altogether, 51 eve…
Diffuse ionized gas toward beta Canis Majoris
Gry, Cecile; Dupin, Olivier
This paper presents the study of the interstellar medium toward beta CMa, a disk sight-line known for its low neutral gas density. This study uses high and medium resolution HST-GHRS spectra including lines from the following species: H i, D i, N i, O i, S ii, S iii, Si ii, Si iii, Si iv, Al ii, Al iii, Fe ii, Mg i, Mg ii, Mn ii, C ii and C iv. Th…
The Theory of Anomalous Cosmic Rays
Giacalone, J.; Jokipii, J. R.
Anomalous cosmic rays are a heliospheric phenomenon in which interstellar neutral atoms stream into the heliosphere, are ionized by either solar radiation or the solar wind, and are subsequently accelerated to very high energies, greater than 1 GeV. Current thinking has the bulk of the acceleration to very-high energies taking place, by the mechan…
The Solar Minimum Active Region 7978, Its X2.6/1B Flare, CME, and Interplanetary Shock Propagation of 9 July 1996
Michels, D. J.; Paswaters, S. E.; Koomen, M. J. +21 more
The first X-class flare in four years occurred on 9 July 1996. This X2.6/1B flare reached its maximum at 09:11 UT and was located in active region 7978 (S10° W30°) which was an old-cycle sunspot polarity group. We report the SOHO LASCO/EIT/MDI and SOONSPOT observations before and after this event together with Yohkoh SXT images of the flare, radio…
The Metallicity of Low-Redshift Lyalpha Forest Clouds
Tytler, David; Barlow, Thomas A.
Using archival Hubble Space Telescope (HST) Faint Object Spectrograph spectra of 15 quasars, we measure an average metallicity for Lyalpha forest absorption clouds between redshifts of 0.3 and 0.8. A composite spectrum of all Lyalpha systems shows an average rest equivalent width of ~0.06 Å for C iv lambda1548.20. This is a factor of 10 larger tha…
Accuracy of Current Density Determination
Robert, Patrick; Dunlop, Malcolm W.; Roux, Alain +1 more
Cassini uvis observations of Saturns rings
Colwell, Joshua E.; Esposito, Larry W.; McClintock, William E.
The Cassini Ultra-violet Imaging Spectrograph (UVIS) is part of the remote sensing payload of the Cassini Orbiter spacecraft. Its science objectives include investigation of the chemistry, clouds, and energy balance of the Titan and Saturn atmospheres ; neutrals in the magnetosphere ; D/H ratio for Titan and Saturn ; and structure and evolution of…
Spectral analysis of the high-gravity extreme helium star LSIV+6 deg2
Jeffery, C. S.
The optical spectrum of the early B hydrogen-deficient star LSIV+6 deg2 has been analysed. With T_eff=31000K, logg=4.05, n_H~10^-4 and n_c~0.1 (relative abundances by number), it is the hottest high-gravity extreme helium star (EHe) yet studied. The Hei spectrum shows all predicted permitted and forbidden transitions in absorption. LSIV+6 deg2 is …
Detection of further UV-bright high-redshift QSOs
Reimers, D.; Hagen, H. -J.; Rodriguez-Pascual, P. +1 more
We present successful UV observations with IUE of several newly discovered high-redshift QSOs from the Hamburg QSO Surveys. In addition to three previously discovered QSOs three new objects have been found to have lines of sight transparent to wavelengths as short as 1200 { Angstroms}: HS 0747+4259 (z = 1.9, V = 15.8); HS 1147+6556 (z = 2.21, V = …
Early-Type Galaxies in the Hubble Deep Field: The <mu_e>-r_e Relation and the Lack of Large Galaxies at High Redshift
Fasano, Giovanni; Cristiani, Stefano; Arnouts, Stephane +1 more
We present the results of detailed surface photometry of a sample of early-type galaxies in the Hubble Deep Field (HDF). Effective radii, surface brightnesses, and total V_606 magnitudes have been obtained, as well as U_300, B_450, I_814, J, H, and K colors, which are compared with the predictions of chemical spectrophotometric models of populatio…