Search Publications
Limitations on suprathermal tails of electrons in the lower solar corona
Geiss, J.; Ko, Y. -K.; Gloeckler, G. +1 more
Measurements of the charge states of solar wind ions by the SWICS instrument on Ulysses are used to place limits on the extent to which the velocity distribution of electrons in the lower solar corona deviates from a Maxwellian distribution by having a suprathermal tail. It is found that the data are consistent with a suprathermal tail which is no…
Discovery of four white dwarfs with strong magnetic fields by the Hamburg/ESO Survey.
Reimers, D.; Jordan, S.; Bade, N. +3 more
Four magnetic white dwarfs have been found in the course of the Hamburg/ESO Survey for bright QSOs. The objects have been selected as QSO candidate on the basis of its blue continuum and the apparent absence of strong hydrogen or helium lines. One star, HE1211-1707, shows a rather fast spectral variability: both the strength and the position of th…
On the Interpretation of the Ultraviolet Spectra of Symbiotic Stars and Recurrent Novae. II. The 1985 Outburst of RS Ophiuchi
Sonneborn, G.; Shore, Steven N.; Starrfield, Sumner +1 more
We discuss the 1985 outburst of the symbiotic recurrent nova RS Oph using spectra obtained with the International Ultraviolet Explorer satellite and contemporaneous ground-based optical spectra. The low- resolution integrated fluxes show that a short-lived constant bolometric luminosity phase existed in the early outburst. If this reached the Eddi…
The abundance of atomic 1H, 4He and 3He in the local interstellar cloud from pickup ion observations with SWICS on Ulysses
Gloeckler, George
Pickup ions measured deep inside the heliosphere open a new way to determine the absolute atomic density of a number of elements and isotopes in the local interstellar cloud (LIC). We derive the atomic abundance of hydrogen and the two isotopes of helium from the velocity and spatial distributions of interstellar pickup protons and ionized helium …
V1974 Cygni 1992: Optical and Ultraviolet Evolution and Analysis
Sonneborn, G.; Shore, S. N.; Starrfield, S. +3 more
We have obtained optical spectrophotometry of V1974 Cygni (Nova Cygni 1992), the brightest nova since 1975, from day 4 to 540 after visual maximum, which we have combined with ultraviolet spectrophotometry to study the ejecta. We show high quality ultraviolet and optical spectra at each major evolutionary phase, identify the lines present during t…
The Intermediate-Mass Population in the Core of the R136 Star Cluster
Holtzman, Jon A.; Lynds, Roger; Groth, Edward J. +3 more
R136, the compact, luminous star cluster at the center of the 30 Doradus nebula, represents an extreme mode of star formation. Yet it is unique among these kinds of objects in that it can be resolved into individual stars and the star formation process probed through the stellar products. In a previous paper we reported on a study of the intermedi…
Cataclysmic and Close Binaries in Star Clusters. IV. The Unexpectedly Low Number of Erupting Dwarf Novae Detected by the Hubble Space Telescope in the Core of 47 Tucanae
Gilliland, Ronald L.; Saha, Abhijit; Shara, Michael M. +2 more
The standard model of tidal capture predicts that ∼45 moderately bright cataclysmic binaries should exist today in 47 Tuc. To test this prediction, we have conducted a search for erupting dwarf novae in the center of 47 Tuc with 12 separate epochs of Hubble Space Telescope (HST) images in visual through near-UV bands. We have found a second erupti…
Extended LY alpha -absorbing Halos around Nearby Galaxies
Bowen, David V.; Pettini, Max; Blades, J. Chris
In order to establish the Lyα absorption cross section of present-day galaxies, we have identified 38 galaxies with z = 0-0.08 that lie within 40-500 h^-1^ kpc of the line of sight to a QSO observed with the Faint Object Spectrograph aboard the Hubble Space Telescope (HST). Including three galaxies in the field of 3C 273 investigated by previous a…
SWS spectroscopy of the colliding galaxies NGC4038/39.
Lutz, D.; Genzel, R.; Sturm, E. +8 more
We present mid-infrared spectroscopy of the prototypical interacting galaxies NGC 4038/39 (the `Antennae') obtained with the ISO Short Wavelength Spectrometer (SWS). Our observations focus on the interaction zone where the two galaxies overlap, providing new constraints on the properties of the young and vigorous extranuclear starburst triggered b…
Secular variations in the Z source CygnusX-2.
van der Klis, M.; Kuulkers, E.; Vaughan, B. A.
We analyzed the X-ray spectral variations of the low-mass X-ray binary CygX-2 on time scales longer than one day using EXOSAT data. We describe these variations in terms of the shifts and shape changes of the "Z" pattern in X-ray colour-colour and hardness-intensity diagrams. CygX-2 varies between three intensity "levels": "high", "medium" and "lo…