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The Axis Ratio Distribution of Faint Galaxies: Evidence for a Population of Dwarf Galaxies at I approximately 20.5
Casertano, Stefano; Im, Myungshin; Griffiths, Richard E. +1 more
The axis ratio distribution of faint galaxies observed by the Hubble Space Telescope (HST) as part of the Medium Deep Survey key project suggests that a very large fraction of the total population at magnitudes I >= 20 mag consists of a class of galaxies with luminosity profile, axis ratio distribution, angular size, and color that resemble loc…
Constraints on Solar Wind Acceleration Mechanisms from ULYSSES Plasma Observations: The First Polar Pass
Phillips, John L.; Barnes, Aaron; Gazis, Paul R.
The mass flux density and velocity of the solar wind at polar latitudes can provide strong constraints on solar wind acceleration mechanisms. We use plasma observations from the first polar passage of the Ulysses spacecraft to investigate this question. We find that the mass flux density and velocity are too high to reconcile with acceleration of …
MG II H and K Profiles in High-Luminosity, Late-Type Stars
Carpenter, K. G.; Robinson, R. D.
Using high-resolution spectroscopic data taken with the Goddard High Resolution Spectrographic (GHRS) aboard the Hubble Space Telescope (HST) and with the International Ultraviolet Explorer (IUE) satellite, we compare the profiles of the Mg II h and k lines seen in stars with spectral types ranging from early K through mid-M and luminosities from …
The evolution of QSO spectra
Koratkar, Anuradha; Francis, Paul J.
We study the rest-frame UV spectra of two samples of QSOs, a low-redshift (z~0.4) sample drawn from the IUE archives, and a high-redshift (z~2.2), optically selected sample, the Large Bright QSO Survey (LBQS). The samples overlap substantially in their range of absolute magnitudes and radio properties, allowing us to study directly the evolution o…
Galaxy Clustering Statistics of Hubble Space Telescope Medium Deep Survey WF/PC Images
Im, M.; Griffiths, R. E.; Casertano, S. +2 more
We investigate the clustering properties of galaxies observed to I ≲ 23 mag in prerefurbishment WF/PC images obtained for the Medium Deep Survey HST Key project. The present study is superior to earlier ground-based galaxy clustering studies in its subarcsecond resolution of close pairs of objects and the depths to which systematic galaxy classifi…
Spectroscopic Orbits for Symbiotic Binaries. III. Eclipses of the Hot Component in RW Hydrae
Mikolajewska, Joanna; Kenyon, Scott J.
We analyze optical and ultraviolet spectroscopic observations of the symbiotic star RW Hydrae. This system contains an M2 giant and a hot white dwarf, Th=8O,OOO K, in an eclipsing binary system with an orbital period of 370.2±0.9d. The component masses are Mg≈0.5-2 Msun for the red giant and Mh≈O.3-O.6 M…
Probing the Galactic Disk and Halo. II. Hot Interstellar Gas toward the Inner Galaxy Star HD 156359
Sembach, Kenneth R.; Savage, Blair D.; Lu, Limin
We present Goddard High Resolution Spectrograph intermediate-resolution measurements of the 1233-1256 A spectral region of HD 156396, a halo star at l = 328.7 deg, b = -14.5 deg in the inner Galaxy with a line-of sight distance of 11.1 kpc and a z-distance of -2.8 kpc. The data have a resolution of 18 km/s Full Width at Half Maximum (FWHM) and a s…
RE 0044+09: A New K Dwarf Rapid Rotator with a White Dwarf Companion?
Brown, Alexander; Jeffries, Robin D.; James, David J. +7 more
We report the discovery of a new K dwarf rapid rotator with a potential white dwarf companion. The white dwarf accounts for over 90% of the observed extreme ultraviolet flux detected from this system. Analysis of ROSAT Wide Field Camera (WFC) and IUE data both suggest a white dwarf temperature of approximately 28,700 K. Optical photometry and the …
Hot subluminous stars at high galactic latitudes. V. UV spectra of binary and peculiar hot subdwarf stars.
de Boer, K. S.; Heber, U.; Moehler, S. +2 more
UV spectra observed with the IUE satellite of hot subdwarfs showing peculiarities in optical spectra are presented. Most peculiarities can be explained by the presence of a cool companion star. Assuming that the UV region is not affected by a cool companion, the fluxes of the hot component of the binary stars are modelled in the UV using theoretic…
Chromospheric Models for ALTAIR (A7 IV--V)
Talavera, A.; Kondo, Y.; Bruhweiler, F. +5 more
The star, Altair (A7 IV-V), is clearly shown to have Lyman-alpha emission of chromospheric origin, while no evidence is found for the Mg II emission reported in previous investigations. We present non-Local Thermodymanic Equilibrium (non-LTE) semiempirical models incorporating partial redistribution of the chromosphere of Altair that reproduce the…