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The absolute magnitudes of Cepheids and the extragalacticdistance scale
Feast, Michael
It is pointed out that a Cepheid period-luminosity relation with a zero-point from Hipparcos trigonometrical parallaxes and a consistent reddening system zero-point implies that some recent estimates of H_0 based on the Cepheid scale should be increased by ~8 per cent. This result avoids using the distance to the Large Magellanic Cloud (LMC) as an…
Extreme Ultraviolet Explorer Investigation of Three Short-Period Binary Stars
Rucinski, Slavek M.
Extreme Ultraviolet Explorer spectroscopic observations (SW, MW, and LW bands, covering 80-160, 170-350, and 300-450 Å with resolutions 0.5, 1, and 2 Å, respectively) and photometric observations (Deep Sky Survey [DSS], broadband 70-140 Å) have been obtained for two contact binaries, 44i Boo B and VW Cep, and one close but detached binary, ER Vul.…
Progressive Star Bursts and High Velocities in the Infrared-luminous, Colliding Galaxy ARP 118
Gao, Yu; Lamb, Susan A.; Hearn, Nathan C.
In this Letter, we demonstrate for the first time the connection between the spatial and temporal progression of star formation and the changing locations of the very dense regions in the gas of a massive disk galaxy (NGC 1144) in the aftermath of its collision with a massive elliptical galaxy (NGC 1143). These two galaxies form the combined objec…
New Optical Fields and Candidates of 10 3C Radio Sources. I. The R-Band Images
Baum, Stefi A.; McCarthy, Patrick J.; Sparks, William B. +6 more
Using new R-band images acquired as part of the 3CR Snapshot Survey with the Wide Field Planetary Camera 2 on the Hubble Space Telescope, we present positive optical identifications of three previously unidentified 3C radio sources (3C 91, 134, and 141). The fields of five others (3C 131, 152, 399.1, 415.2, and 468.1) are also presented with tenta…
HST Spectroscopy of PG 1159 Stars: the Boundary of the GW VIR Instability Strip
Dreizler, S.
Our recent analysis of PG 1159 stars, mainly based on the HST spectroscopy, is presented. The results allow several conclusions regarding the boundary of the GW Vir instability strip and the driving mechanism for these pulsations.
Weak lensing analysis of CL 1358+62
Franx, Marijn; Hoekstra, Henk; Kuijken, Konrad +1 more
We report on the detection of weak gravitational lensing of faint, distant background objects by Cl 1358+62, a rich cluster of galaxies at a redshift of z = 0.33. The observations consist of a multicolor mosaic of 12 WFPC2 pointings of the Hubble Space Telescope (HST). We find a projected mass of (4.4±0.6) × 10 14 M ⊙ within …
Hubble Space Telescope Observations of Planetary Nebulae in the Magellanic Clouds. VI. Cycles 4 and 5 Ultraviolet Spectroscopy Using the Faint Object Spectrograph
Ford, H. C.; Harrington, J. P.; Wood, P. R. +6 more
The Faint Object Spectrograph on board the Hubble Space Telescope (HST) is used to obtain spectra in the wavelength range λλ1150-4800 of three planetary nebulae in the Small Magellanic Cloud and 10 planetary nebulae in the Large Magellanic Cloud. This sample extends the sample of 12 objects previously observed with HST and reported in the third pa…
The Mass of the Cepheid Binary V636 Scorpii
Albrow, Michael D.; Cottrell, P. L.; Evans, N. R. +4 more
The mass-luminosity relation for Cepheids depends on the degree of mixing in their main-sequence progenitors. Masses of Cepheids can be inferred by using different aspects of pulsation theory. These methods have in the past led to diverging results, showing that something was wrong in either evolution theory or pulsation theory or both. For some b…
High velocity gas and dust evolution in Chamaeleon clouds
Boulanger, Francois; Falgarone, Edith; Gry, Cecile +2 more
We report on GHRS observations which reveal conspicuous differences in the absorption spectra of two nearby stars, close to each other. The star HD102065 lies behind a cloud in Chamaeleon with unusually strong mid-IR emission, indicating a large abundance of very small dust particles. Along this line of sight, 5% of the gas (about 6 10(19) cm(-2) …
CCD photometry of variable stars in the Magellanic Clouds - VI. The eclipsing binary HV982 in the Large Magellanic Cloud
Guinan, E. F.; Pritchard, J. D.; Tobin, W. +1 more
Using improved techniques, high-quality CCD uvbyVI photometry has been obtained for the eclipsing binary HV982 in the Large Magellanic Cloud (LMC). International Ultraviolet Explorer ultraviolet spectrophotometry was also obtained. These data have been analysed using the Wilson-Devinney synthetic light-curve code and Kurucz low-metallicity model a…