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On the reality of a boundary in the H-R diagram between late-type stars with and without high temperature outer atmospheres.
Stencel, R. E.; Linsky, J. L.; Simon, T.
The Linsky-Haisch hypothesis (1979) that a boundary exists in the H-R diagram separating yellow giants from red giants and supergiants is tested. IUE 1150-2000 A low-resolution spectra of 10 stars chosen to constitute a reverse bias sample are presented and discussed. Despite the bias, weak C IV emission indicative of high-temperature plasma was o…
IUE observations of NGC 4649, an elliptical galaxy with a strong ultraviolet flux.
Capaccioli, M.; Oke, J. B.; Bertola, F.
As in the previously studied elliptical galaxies, the flux f(lambda) in NGC 4649 has a minimum at 2500 A followed by a rapid increase towards shorter wavelengths. In NGC 4649, the flux level of this rising branch is the highest so far observed and seems not to be correlated with the luminosity or activity in the galaxy. The excess shortward of 400…
On the linearity of the SWP camera of the IUE : a correction algorithm.
Bohlin, R. C.; Cassatella, A.; Schiffer, F. H. +2 more
An algorithm is presented for correcting IUE low resolution spectral images obtained with the SWP camera for some of the non-linearity effects reported by Bohlin et al. (1980). The non-linearity problem, which affects SWP images processed at Goddard Space Flight Center in the period May 22, 1978 to July 7, 1979 and at VILSPA in the period June 14,…
IUE ultra-violet spectrophotometry of 15 galactic Wolf-rayet stars.
Schmutz, W.; Nussbaumer, H.; Willis, A. J. +1 more
Low-resolution IUE ultraviolet spectrophotometry is presented of 15 galactic WR stars, covering most subtypes in the WN and WC sequences. The data are presented both as spectral plots and as tabulations of the observed absolute flux distributions covering the wavelength range of 1150-3090 A. The characteristics of these UV WR spectra are discussed…
Shell and photosphere of OMI ORI E : new observations and improved model.
Groote, D.; Hunger, K.
Phase-dependent IR fluxes in the J, H, K, L, and M bands, together with visual spectrograms and IUE spectra, are used to study the helium-rich star Sigma Ori E. An effective temperature of about 22,500 K is derived, along with an angular diameter of 0.079 milliarcsec, a surface gravity of log g equals 3.85, and a mass of approximately 3 solar mass…
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…
P-Cyg profiles observed in the ultraviolet and visible spectra of Wolf-Rayet stars.
Willis, A. J.
A semi-qualitative analysis of the UV P-Cygni line profiles observed in the IUE spectra of seven WN and three WC Wolf-Rayet stars is presented. The velocity characteristics of these profiles are presented and combined with complementary measurements from visible spectra, allowing an inspection of P-Cygni profiles encompassing a wide range of ionic…
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. …