Search Publications
A Magnitude-limited Survey of Cepheid Companions in the Ultraviolet
Evans, Nancy R.
Results of a magnitude-limited survey of classic Cepheids brighter than 8th mag carried out to search for hot main-sequence companions are presented. Spectra of 76 stars obtained with the IUE satellite in the 2000-3200-A region were compared with the spectra of nonvariable supergiants and also the single Cepheid Delta Cep to search for excess flux…
LY alpha Emission from Cooling Flows and Measures of the Dust Content of Rich Clusters of Galaxies
Hu, Esther M.
We tabulate Ly α and UV continuum fluxes from measurements across the emission-line regions of 10 "cooling flow" clusters of galaxies. Comparison of Ly α emission fluxes obtained with the IUE satellite with optical Balmer emission fluxes is used to demonstrate that the lines of sight to the centers of these clusters show an average excess reddenin…
Hubble Space Telescope Faint Object Spectrograph and Ground-based Observations of the Broad Absorption Line Quasar 0226-1024
Turnshek, David A.; Burbidge, E. M.; Morris, Simon L. +6 more
Faint Object spectrograph data from the Hubble Space Telescope of the broad absorption line quasar 0226 - 1024 have revealed the presence of 8-10 absorbing ions between 680 and 1000 A (restframe): C III, N III, N IV, O III, O IV, O VI, S V, S VI, possibly Ne VIII, and possibly O V^*^ arising from a metastable excited state. We also present ground-…
A Prediction of the gamma -Ray Flux from Nova Herculis 1991
Truran, James W.; Shore, Steven N.; Sonneborn, George +3 more
UV observations made with the IUE satellite of Nova Her 1991 are presented and discussed. A distance of 3.4 kpc and reddening of 0.6 E(B-V) to Nova Her 1991 are determined by comparing its UV and optical outburst behavior with those of the extragalactic ONeMg nova LMC 1990 No. 1. Her 1991 was also detected by Rosat five days into its outburst, and…
The Nature of the Recurrent Nova T Coronae Borealis: Ultraviolet Evidence for a White Dwarf Accretor
Cassatella, Angelo; Gilmozzi, Roberto; Selvelli, Pier L.
Data from eleven years of IUE observations of T CrB during its quiescent phase suggest that a white dwarf accretor rather than a main-sequence star is the hot component of the system. The spectroscopic and photometric behavior of T CrB during the 1946 outburst actually supports the interpretation of a thermonuclear runaway event on a massive white…
Evolving, Dynamical Models for Collapsed-Core Globular Clusters: M15 and NGC 6624
Cohn, Haldan N.; Lugger, Phyllis M.; Murphy, Brian W. +1 more
The stellar populations of the collapsed-core globular clusters M15 and NGC 6624 are investigated by fitting observed surface-brightness and projected velocity-dispersion profiles. The present evolving cluster models were generated by the direct Fokker-Planck method and incorporate realistic stellar mass spectra and energy input from binaries form…
Spherically Symmetric, Expanding, Non--LTE Model Atmospheres for Novae during Their Early Stages
Hauschildt, P. H.; Starrfield, S.; Wehrse, R. +1 more
In the continuum and line-blanketed models presented here, nova atmospheres are characterized by a very slow decrease of density with increasing radius. This feature leads to very large geometrical extensions so that there are large temperature differences between the inner and outer parts of the line-forming regions. The theoretical spectra show …
A Multiwavelength Study of Nova QU Vulpeculae 1984
Williams, Robert E.; Truran, James W.; Ferland, Gary J. +6 more
We have combined ground-based optical and satellite ultraviolet spectrophotometric data to study the ejected shell of Nova Vulpecula 1984 No. 2 (QU Vul). Substantial uncertainties concerning the nature of the ionizing continuum, and the role played by density inhomogeneities, now exist. Because of these uncertainties, the chemical composition is d…
Fractionation of CO in the Diffuse Clouds toward zeta Ophiuchi
Federman, S. R.; Lambert, David L.; Cardelli, Jason A. +1 more
An analysis of CO A-X bands in diffuse clouds toward Zeta Ophiuchi is presented. The results provide isotopic ratios that constitute the strongest observational evidence for highly localized isotopic fractionation of CO in diffuse portions of an interstellar cloud. The value of the fractionation implies that selective photodissociation is the cont…
Ultraviolet, Optical, and Infrared Observations of the High-Latitude Molecular Cloud toward HD 210121
Welty, Daniel E.; Fowler, James R.
Low-resolution UV spectra of the B3 V star HD 210121, located behind the high-latitude molecular cloud DBB 80, yield an extinction curve exhibiting a far-UV rise that is among the steepest known. The apparently simple line of sight affords an excellent opportunity for investigating the absorption and emission characteristics of a single, isolated …