Search Publications
The ultraviolet spectrum of the Crab nebula.
Davidson, K.; Gull, T. R.; Kafatos, M. +6 more
Ultraviolet spectroscopy of the Crab Nebula done by the International Ultraviolet Explorer satellite is described, and an estimate of the carbon abundance is made, noting data reduction to remove spectral defects caused by radiation hits. The important C IV 1549, He II 1640, and semiforbidden C III 1908 emission line intensities were measured and …
Ultraviolet observations of stellar chromospheric activity.
Raymond, J. C.; Dupree, A. K.; Hartmann, L.
A survey is presented of chromospheric and transition region (TR) line emission in late-type stars obtained with the IUE satellite. A wide variation in TR emission (ions formed near T = 100,000 K) at a given position in the H-R diagram is found, contradicting theories that incorporate only acoustic energy generation and deposition. The behavior of…
The scattering phase function of interstellar grains : the case of the reflection nebula NGC 7023.
Bohlin, R. C.; Witt, A. N.; Stecher, T. P. +1 more
IUE observations of the reflection nebula NGC 7023 and the illuminating star, HD 200775, in the spectral range from 1300 to 3100 A are combined with ground-based measurements of the nebular brightness distribution at 3500, 4100, 4700, and 5500 A to determine the scattering properties of the nebular dust grains. Total nebular fluxes are derived fro…
The 12 CO/13 CO abundance ratio toward ZET Oph.
Jenkins, E. B.; Wannier, P. G.; Penzias, A. A.
The CO-12/CO-13 abundance ratio toward Zeta Ophiuchi, and interstellar material physical properties, are determined by means of a system of UV absorption lines gathered by Copernicus and IUE spacecraft observations. The observations imply a low CO isotope ratio, at 55 + or - 11, and a CO-12 column density of 2.4 + or - 0.3 x 10 to the 15th/sq cm. …
Ultraviolet and optical spectrum studies of lambda Andromedae : evidence for atmospheric inhomogeneities.
Dupree, A. K.; Baliunas, S. L.
To pursue the study of solar phenomena in cool stars, chromospheric activity in Lambda Andromedae (HD 222107 has been investigated). This binary, whose primary star is G7-G8 IV-III, shows strong chromospheric emissions and is related to the RS CVn-type systems. The first quantitative measurements of chromospheric and solar-type transition-region e…
RW Sex, a disk with a hot, high-velocity wind.
Oke, J. B.; Greenstein, J. L.
The continuum spectrum of the flickering blue variable RW Sex was observed from 10,000 to 1150 A. The star is a cataclysmic variable currently stabilized at maximum, and the spectrum is dominated by an accretion disk, with flat spectrum in the ultraviolet, except at more than 5000 A, where a blackbody near 7000 K is seen. A distance of 400 pc is d…
Discovery of highly ionized species in the ultraviolet spectrum of Feige 24.
Raymond, J. C.; Dupree, A. K.
A high-resolution ultraviolet spectrum of the nearby (90 pc) white dwarf binary Feige 24 (DA + M1-2 V) obtained with the International Ultraviolet Explorer satellite (IUE) reveals two sets of absorption features in the species C IV, Si IV, and N V. The low-velocity component (V approximately 1 km/s) arises from the local interstellar gas apparentl…
OH fluorescence in comets - Fluorescence efficiency of the ultraviolet bands
A'Hearn, M. F.; Schleicher, D. G.
The present investigation is concerned with the calculation of the fluorescence efficiency of OH over a wide range of heliocentric radial velocities. Three vibrational states in each of the two lowest electronic states are included in these calculations, producing a total of nine vibrational bands in the ultraviolet. The attempt is made to reprodu…
Energy distribution in the strongly interacting binary system SX Cas.
Weiland, J. L.; Koch, R. H.; Plavec, M. J.
IUE spectra and optical scans covering the 110-680 nm interval were obtained in a search for a source which would resolve the anomalous presence of strong Balmer emission lines in the SX Cas eclipsing binary system, which is inconsistent with the usual spectral classification of the components as A6 III + G6 III. The IUE spectra unexpectedly show …
Two multifrequency observations of the BL Lacertae object OJ 287
Bruhweiler, F. C.; Sitko, M. L.; Worrall, D. M. +8 more
Results are reported for various sets of X-ray, UV, visual, IR, millimeter, and radio observations of OJ 287. The spectral information is used to constrain nonthermal energy production models for the source, and three possible models are considered. It is found that, in order to describe all the observed flux in the radio to X-ray bands with a syn…