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The Ultraviolet Spectrum of the Liner NGC 4579
Filippenko, A. V.; Ho, L. C.; Reichert, G. A. +4 more
We present a Hubble Space Telescope ultraviolet spectrum of the LINER nucleus of NGC 4579, spanning the wavelength range 1160-3270 A. The data reveal a low-excitation spectrum of narrow (FWHM ~1200 km s^-1^) and broad (FWHM ~ 6600 km s^-1^) emission lines, which provide new diagnostics of the physical conditions within the emission-line regions. A…
Perspectives in Helioseismology
Scherrer, P. H.; Toomre, J.; Gough, D. O. +1 more
Helioseismology is probing the interior structure and dynamics of the sun with ever-increasing precision, providing a well-calibrated laboratory in which physical processes can be studied under conditions that are unattainable on Earth. Nearly 10 million resonant modes of oscillation are observable in the solar atmosphere, and their frequencies ne…
Stellar Variability in the Central Populations of 47 Tucanae from WF/PC Observations with the Hubble Space Telescope. II. Binary Systems
Gilliland, Ronald L.; Saha, Abhijit; Shara, Michael M. +3 more
Stars in the core of 47 Tuc have been intensively surveyed for variability, using differential time series photometry, with the Planetary Camera of the Hubble Space Telescope. Some 20,000 stars were surveyed in the U band (F336W) in a 66" x 66" field centered on the core of 47 Tuc, with almost continuous observing over 38.5 hr, and using 1000 s ex…
WFPC2 Observations of the Cooling Flow Elliptical in Abell 1795
Casertano, Stefano; Holtzman, Jon; Ballester, Gilda E. +16 more
We present WFPC2 images of the core of the cooling flow cD galaxy in Abell 1795. An irregular, asymmetric dust lane extends 7 h^{-1}75 kpc in projection to the north-northwest. The dust shares the morphology observed in the H alpha and excess UV emission. We see both diffuse and knotty blue emission around the dust lane, especially at t…
Hubble Space Telescope Imaging and Polarimetry of NGC 5128 (Centaurus A)
Capetti, A.; Sparks, W. B.; Macchetto, F. +2 more
We present imaging and polarimetry of NGC 5128 in the R and I bands obtained using the Hubble Space Telescope (HST) Wide Field Planetary Camera. The morphology and polarization properties of NGC 5128 at these wavelengths are dominated by the presence of the dust lane. The apparent V-band extinction ranges from 0.5 to 7 mag. The overall pattern of …
Detection of an absorption feature at the position of the 4.27-µm band of solid CO_2_.
Henning, T.; Lemke, D.; Pfau, W. +3 more
We report observations of 13 young infrared sources associated with molecular clouds with ISO's spectrophotometer ISOPHOT-S in the wavelength range from 2.5 to 11.6µm. In addition to a number of well-known interstellar bands due to various molecular ices, a new band at 4.27µm was detected, which is very likely attributed to C=O stretch…
The 1990 May 24 Solar Cosmic-Ray Event
Vainio, R.; Torsti, J.; Anttila, A. +2 more
This paper presents an integrated analysis of GOES 6, 7 and neutron monitor observations of solar cosmic-ray event following the 1990 May 24 solar flare. We have used a model which includes particle injection at the Sun and at the interplanetary shock front and particle propagation through the interplanetary medium. The model does not attempt to s…
The Distance to Two Neutral Hydrogen Clouds: The High-Velocity Complex A and the Low-Latitude Intermediate-Velocity Cloud
Danly, Laura; Wakker, Bart; Wilhelm, Ronald +5 more
A lower limit to the distance of the high-velocity cloud (HVC) complex A of 4 kpc (z > 3 kpc) is derived. The HVC is detected toward the Seyfert galaxy Mrk 106 in Mg II λλ2796, 2803 absorption spectra taken with Hubble Space Telescope (HST) proving that Mg^+^ is present in the cloud. It is not detected in the Mg II spectra of two stars, PG 0859…
Hubble Space Telescope Observations of QSO Absorption Lines Associated with Starburst Galaxy Outflows
Bowen, David V.; Danly, Laura; Norman, Colin A. +2 more
In order to study the physical state of outflows from starburst galaxies, we have been obtaining spectra of QSOs located behind possible starburst outflows and searching for UV absorption by low-ionization gas. We have detected strong and probably complex Mg II, Mg I, and Fe II absorption arising from gas in the outer envelope of the starburst gal…
Plasma flow in the Jovian magnetosphere and related magnetic effects: Ulysses observations
Dougherty, M. K.; Balogh, A.; Forsyth, R. J. +6 more
The plasma flow in Jupiter's magnetosphere observed during the Ulysses flyby is compared with previous Pioneer, Voyager and ground-based observations. These data show that near-rigid corotation is enforced in the inner magnetosphere, but that the azimuthal flow plateaus at 150-300 kms-1 in the middle magnetosphere plasma sheet beyond ~2…