Search Publications
On the High-Energy Gamma-Ray Signature of Cosmic-Ray Sources
Ormes, J. F.; Ozel, M. E.; Morris, D. J.
If cosmic rays are accelerated by strong shocks, then cosmic-ray sources should be characterized by spectra, dN/dE is proportional to p^-(2.0-2.2)^, reflecting the strength of those shocks. This is expected from the "standard leaky box" model of cosmic-ray propagation in which the source spectra are harder than the observed spectra because higher …
EXOSAT and IUE Observations of SW UMa during Superoutburst
Szkody, Paula; Hassall, B. J. M.; Osborne, Julian
IUE and Exosat observations obtained during the March 1986 superoutburst of the SU UMa type dwarf nova SW UMa are presented. The observations show the presence of a hot, extensive, optically thick disk. The UV fluxes show an increase of 1000 over the quiescent values, implying a large increase in mass accretion rate. The Exosat obserations show an…
Hot Components and Circumstellar Grains in M Supergiant Syncretic Binaries
Buss, Richard H., Jr.; Snow, Theodore P., Jr.
The authors have aqcquired ultraviolet spectra and infrared data to study grains in cool star plus hot star syncretic (VV Cep) type binaries. Though M supergiants almost always have circumstellar grains, the authors found grains, from IRAS infrared photometry, in only about half of the syncretic systems. Infrared spectra revealed that the circumst…
The Abundance of Zinc in Hg-Mn Stars
Sadakane, Kozo; Takada-Hidai, Masahide; Jugaku, Jun
The resonance line of singly ionized zinc (Zn II) at 2062.00 A is quantitatively analyzed, and the abundances of Zn in atmospheres of early-type stars have been determined for the first time. The line is analyzed in IUE spectra of six reference (normal) stars between spectral types B5 and A0 and of 23 Hg-Mn stars. The abundances of Zn in the refer…
IUE Spectroscopy of U Cephei during the Mass Flow Outburst of 1986 June
Kondo, Yoji; McCluskey, George E., Jr.; Olson, Edward C.
The interacting Algol-type binary U Cep underwent another of its irregularly occurring transient high-mass flow events during June 1986. For the first time, high-resolution ultraviolet spectroscopy of U Cep during such an event was possible. High-resolution spectra in the far-ultraviolet and near-ultraviolet were obtained with IUE. These spectra s…
The Atmospheric Eclipse of 31 Cygni in the Ultraviolet
Eaton, Joel A.
Theoretical spectra have been compared with high-dispersion IUE observations for the 1982 atmospheric eclipse of 31 Cyg (B4 V + K4 Ib). Chromospheric column densities, excitation temperatures, turbulence, and ionization are determined. It is found that temperature increases with height in the chromosphere, showing a range 5000 - 14,400K for four l…
The Ionization Structure of Planetary Nebulae. VIII. NGC 6826
Barker, Timothy
Spectrophotometric observations of emission-line intensities over the spectral range 1400 to 1700 A were made in seven positions in the planetary nebulae NGC 6826. The O(++) electron temperature varies little from 8900 K throughout the nebula; the Balmer continuum electron temperature averages 1500 K higher. The wavelength 4267 C II line intensiti…
The Complex Wind of the Central Star of the Planetary Nebula Abell 78
Feibelman, Walter A.; Kaler, James B.; Henrichs, H. F.
The authors have observed with the high-dispersion camera of the IUE the broad P Cygni profiles of C IV, N V, and O V that arise from Abell 78's nucleus. They find a terminal velocity to the wind that is close to 3670±30 km s-1, a positive velocity gradient, and an approximate mass loss rate of ≡4×10-9M_sun;yr-1. S…
The Ultraviolet-Optical-Infrared Energy Distribution of LMC X-3: Observation of an Accretion Disk around a Black Hole
Maraschi, L.; Tanzi, E. G.; Chiappetti, L. +4 more
LMC X-3 was observed quasi-simultaneously at UV (IUE), optical, and IR (ESO, La Silla) frequencies in 1987 January. The overall energy distribution exhibits a broad peak around 10^15^ Hz. The UV flux appears well in excess of that measured by us in 1986 March, which can be attributed to the noncollapsed star in the system. The excess emission can …
Quasi-simultaneous Ultraviolet Optical and Infrared Observations of the BL Lacertae Object PKS 0048-09
Maraschi, L.; Tanzi, E. G.; Bouchet, P. +2 more
The first International Ultraviolet Explorer (IUE) observations of the BL Lacertae object PKS 0048-09 were obtained on 1987 January 7 and 8, when the object was in a moderately high optical state (m_v_ ~ 15.5 mag). Quasi-simultaneous optical-IR spectrophotometry allows deriving the detailed energy distribution from ~10^14^ to ~2.5 x 10^15^ Hz. Com…