Search Publications
A Test of Synthetic Accretion Disk Spectra Using Ultraviolet Flux Distributions of Nova-like Variables
Wade, Richard A.
Ultraviolet (UV) fluxes and other data for a sample of nine novalike cataclysmic variables are assembled from the literature. The UV fluxes and colors are compared to spectra of steady state model accretion disks, constructed using either Planck functions or model stellar atmosphere spectra as elementary radiators. Deficiencies are found with both…
Colliding Stellar Winds in the Eclipsing Wolf-Rayet Binary V444 Cygni
Shore, Steven N.; Brown, Douglas N.
High resolution spectra of V444 Cygni have been obtained using the International Ultraviolet Explorer Satellite. These spectra span both eclipses and include one observation at third quadrature. Together with seven archival spectra, they provide reasonably complete phase coverage for the system. The variations in the P Cygni profiles of the He(II)…
The Abundances of Carbon and Nitrogen in I ZW 18
Garnett, Donald R.; Dufour, Reginald J.; Shields, Gregory A.
We present IUE and McDonald IDS spectrophotometry of the NW H II region in the most oxygen-poor galaxy known, I Zw 18. The C III] λ1909 and [N II] λ6583 emission lines were detected for the first time in this galaxy. Using a photoionization model for the H II region, we derive 12 + log N(X)/N(H) = 6.94 +/- 0.24 for C, 5.99 +/- 0.16 for N, and 7.24…
Measurements of the Gas Temperature and Iron Abundance Distribution in the Coma Cluster
Hughes, John P.; Gorenstein, P.; Fabricant, D.
The medium energy X-ray detectors onboard the EXOSAT Observatory have been used to determine the gas temperature at several positions in the Coma Cluster of galaxies. We find evidence at greater than 95% confidence for a higher temperature in the center of the cluster than in a position approximately 45' off-center. No difference in iron abundance…
IUE Observations of Z Andromedae: Spectral Variations during Quiescence and a Physical Model
Fernandez-Castro, Telmo; Cassatella, Angelo; Gimenez, Alvaro +1 more
The authors describe the results of an extensive monitoring of the ultraviolet spectrum of the symbiotic star Z And based on high- and low-resolution IUE observations made during 1978 - 1982, when the star was in a phase of quiescence. Large variations of the Balmer continuum and emission-line intensities where observed on a time scale of about 76…
4U 1626-67: The Binary with the Smallest Known Mass Function
van der Klis, M.; Verbunt, F.; Rappaport, S. +3 more
The pulsating X-ray source 4U 1626-67 is an accreting neutron star in a binary system with a very low mass companion. The authors observed the source with EXOSAT continuously for 23 hr on 1986 March 30 - 31 UT. These observations allow them to set a stringent upper limit on the projected semimajor axis of the orbit of the neutron star. The corresp…
Hard X-Ray Emission from a Type 2 Seyfert Galaxy (NGC 1068)
Elvis, Martin; Lawrence, A.
EXOSAT observations of the type 2 Seyfert galaxy NGC 1068 have detected a source in the 2-10 keV range with a flux density at 2 keV of 0.6 microJy. It has a flat (α_E_ = 0.62 +/- 0.25) power-law spectrum similar to type 1 Seyferts; Combined with Low Energy EXOSAT filter data and Einstein IPC observations, these data show that spectral curvature is…
The Reionization of Unshocked Ejecta in SN 1006
Fesen, Robert A.; Hamilton, Andrew J. S.
The validity of carbon-deflagration models white dwarf models for type Ia supernovae is investigated by examining whether most of the iron in the center of SN 1006 exists in forms other than Fe II, such as iron grains or other ionic stages of iron, as the models require. The possible ways in which iron can be hidden in SN 1006 are reviewed, and an…
X-Ray, Optical, and Infrared Luminosity Correlations in Radio-quiet Quasars
Kriss, Gerard A.
For a sample of 88 radio-quiet quasars that includes 15 X-ray upper limits, I find that the X-ray and IR luminosities follow a significantly nonlinear relation (L_2keV_ ~ L^0.73^_1 micron_) that is consistent with that found for the X-ray and optical luminosities. The redshift dependence is weak and may be nonexistent. The shape of the optical thr…
An Ultraviolet Spectral Atlas of Interstellar Lines toward SN 1987A
Panagia, N.; Grewing, M.; Wamsteker, W. +3 more
We present a spectral atlas of the interstellar spectrum toward SN 1987A in the Large Magellanic Cloud. The data used in constructing the atlas were obtained with the IUE satellite as part of the ESA Target of Opportunity Program for observing bright supernovae and were collected within the first few days following discovery of SN 1987A. At that t…