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Investigation of the variability of bright Be stars using HIPPARCOS photometry
Floquet, M.; Hubert, A. M.
The high accuracy and the homogeneity of Hipparcos data for bright stars have allowed us to quantify the degree of variability of Be stars. This degree has been found to be highly dependent on the temperature of the star. Rapid variability is the main feature of the 86% of early Be and less than 20% of late Be stars taking into account the limit o…
Wide Field Planetary Camera 2 Observations of Leo A: A Predominantly Young Galaxy within the Local Group
Saha, A.; Gallagher, J. S.; Cole, A. A. +6 more
The unprecedented detail of the Wide Field Planetary Camera 2 (WFPC2) color-magnitude diagrams (CMDs) of the resolved stellar population of Leo A presented here allows us to determine a new distance and an accurate star formation history for this extremely metal-poor Local Group dwarf irregular galaxy. From the position of the red clump, the heliu…
Hubble Space Telescope imaging of Jupiter's UV aurora during the Galileo orbiter mission
Gérard, Jean-Claude; Clarke, John T.; Ben Jaffel, Lotfi
Hubble Space Telescope (HST) Wide-Field Planetary Camera 2 (WFPC 2) images of Jupiter's aurora have been obtained close in time with Galileo ultraviolet spectrometer (UVS) spectra and in situ particles, fields, and plasma wave measurements between June 1996 and July 1997, overlapping Galileo orbits G1, G2, G7, G8, and C9. This paper presents HST i…
Hubble Space Telescope Observations of Neutron-Capture Elements in Very Metal Poor Stars
Truran, James W.; Sneden, Christopher; Cowan, John J. +1 more
Using the Goddard High-Resolution Spectrograph (GHRS) of the Hubble Space Telescope (HST) we have detected the neutron-capture elements osmium, platinum, and lead in the very metal poor ([Fe/H] ~= -2.8) Galactic halo star HD 115444. This star joins the metal-poor giant HD 126238 ([Fe/H] ~= -1.7) as the second Galactic halo star for which ``third n…
Kinematics of the Nuclear Ionized Gas in the Radio Galaxy M84 (NGC 4374)
Kimble, R.; Kraemer, S.; Green, R. F. +17 more
We present optical long-slit spectroscopy of the nucleus of the nearby radio galaxy M84 (NGC 4374 = 3C 272.1) obtained with the Space Telescope Imaging Spectrograph aboard the Hubble Space Telescope. Our spectra reveal that the nuclear gas disk seen in the Wide Field Planetary Camera 2 imaging by Bower et al. is rotating rapidly. The velocity curv…
The EC 14026 stars - VIII. PG 1336-018: a pulsating sdB star in an HWVir-type eclipsing binary
O'Donoghue, D.; Kilkenny, D.; Lynas-Gray, A. E. +2 more
The sdB star PG 1336-018 is found to be a very short-period eclipsing binary system, remarkably similar to the previously unique system HW Vir. In addition, and unlike HW Vir, the sdB star in the PG 1336 system shows rapid oscillations of the type found in the recently discovered sdB pulsators, or EC 14026 stars. The orbital period, 0.101 0174 d, …
Spectral analyses of PG 1159 star: constraints on the GW Virginis pulsations from HST observations
Dreizler, S.; Heber, U.
We present the results of a quantitative analysis of UV and optical spectra of nine PG 0122+200ls, very hot hydrogen-deficient [pre-] white dwarfs, by means of line blanketed NLTE model atmospheres. Four programme stars constitute the GW Vir variables, a class of non-radial g-mode pulsators. Precise effective temperatures, carbon, nitrogen and oxy…
FLIERs and Other Microstructures in Planetary Nebulae. IV. Images of Elliptical PNs from the Hubble Space Telescope
Perinotto, Mario; Balick, Bruce; Hajian, Arsen R. +3 more
We report new results from high spatial resolution Wide Field Planetary Camera 2 imaging studies of ``FLIERs'' and other microstructures in the planetary nebulae NGC 3242, 6826, 7009, and 7662. Most FLIERs have head-tail morphologies, with the tails pointing outward from the nucleus. Ionization gradients that decrease with distance from the nebula…
Wide Field Planetary Camera 2 Imaging of the Globular Cluster System of the S0 Galaxy NGC 3115
Kundu, Arunav; Whitmore, Bradley C.
Using the Wide Field Planetary Camera 2 on board the Hubble Space Telescope we have identified 144 globular cluster candidates in the inner region of the S0 galaxy NGC 3115. The color distribution of the globular clusters is bimodal, with a blue peak at V-I = 0.96 mag and a red peak at V-I = 1.17 mag. There are roughly equal number of blue and red…
Early-Type Galaxies in the Hubble Deep Field: The Star Formation History
Franceschini, Alberto; Bressan, Alessandro; Fasano, Giovanni +4 more
We have investigated the properties of a complete K-band selected sample of 35 elliptical and S0 galaxies brighter than K = 20.15 mag in the Hubble deep field, as representative of the field galaxy population. This sample has been derived from deep K-band image by the KPNO-IRIM camera, by applying a rigorous morphological classification scheme bas…