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The optical and ultraviolet spectrum of the planetary nebula NGC 2440.
Czyzak, S. J.; Shields, G. A.; Keyes, C. D. +1 more
New measurements of the optical and ultraviolet emission-line intensities of the high-excitation planetary nebula NGC 2440 in the wavelength range 1240-8578 A are analyzed with the aid of photoionization models. The observed O III and N II forbidden-line temperatures (13,800 K and 10,000 K, respectively) differ by more than the models predict. Inc…
Physical conditions in the nucleus of M 81.
Torres-Peimbert, S.; Peimbert, M.
IUE and visual observations of the emission lines in the nucleus of M8 1 are presented. The permitted lines show broad and narrow features qualitatively similar to those in Seyfert galaxies. The observed luminosity for the broad component is L(Hβ) = 7.4 × 1037 ergs s-1, which is about two orders of magnitude smaller than in t…
Ultraviolet observations of hot stars with circumstellar dust shells.
Savage, B. D.; Sitko, M. L.; Meade, M. R.
Absolute fluxes over the wavelength range 1200-3200 A are presented for 13 normal early-type stars and 12 early-type stars known to have large IR excess; the data were obtained to study the UV spectral modifications produced by absorbing circumstellar dust particles. It is found that all the Be/shell stars whose spectral types are later than B6 ex…
Coordinated X-ray, ultraviolet and optical, observations of AM Her, UGem and SS Cyg.
Branduardi-Raymont, G.; Fabbiano, G.; Raymond, J. +3 more
Simultaneous and quasi-simultaneous optical, UV and X-ray observations of the accreting degenerate dwarf stars AM Herculis, U Geminorum and SS Cygni are reported. The observations were obtained in March 1979, by instruments on board the Einstein Observatory and the IUE satellite, and optical properties were monitored on the ground. AM Her was foun…
Extragalactic H II regions in the UV : implications for primeval galaxies.
Terlevich, R.; Meier, D. L.
Three extragalactic regions of rapid star formation with redshifts great enough to separate the Lyman-alpha region from geocoronal Lyman-alpha have been observed with the IUE satellite. Only the low metal abundance object had detectable Lyman-alpha emission with Lyman-alpha/H-alpha of about 6; the other two have Lyman-alpha/H-alpha less than 0.6 (…
Outer atmospheres of cool stars. VIII. IUE observations and chromospheric models for the supergiant stars beta Draconis, epsilon Geminorum and alpha Orionis.
Eriksson, K.; Linsky, J. L.; Basri, G. S.
A semiempirical modeling of stellar chromospheres is extended to late-type supergiants, where computations match high-resolution, absolute-flux profiles of the Ca II K and Mg II h and k lines. IUE UV spectra of Epsilon Gem and Alpha Ori show no evidence of emission lines formed at temperatures greater than 10,000 K, leading to the computation of c…
Ultraviolet spectroscopy of the recurrent nova U SCO during outburst.
Gallagher, J. S.; Williams, R. E.; Truran, J. W. +3 more
Observations of the recurrent nova U Sco during the 1979 outburst are presented, and the spectral evolution is found to differ from that of other recurrent novas. Spectra are dominated by emission lines, and the strong forbidden-line emission characteristic is conspicuously absent. A method to determine masses of nova shells is outlined, and an an…
Ultraviolet interstellar extinction toward 1367 stars observed by ans.
Savage, B. D.; Meyer, D. M.
Five-band UV photometry is used to investigate the character of interstellar extinction toward 1367 stars of spectral type B3 and earlier, with observations producing a galactic average of 5.11, 4.78, 6.52, 4.10 and 1.95 at 1550, 1800, 2200, 2500, and 3300 A, respectively. Differences in the strengths of the UV extinction features of these stars a…
Detailed empirical models for the winds of early-type stars.
Olson, G. L.; Castor, J. I.
Owing to the recent accumulation of ultraviolet data from the IUE satellite, or X-ray data from the Einstein (HEAO 2) satellite, of visible data from ground based electronic detectors, and of radio data from the Very Large Array (VLA) telescope, it is becoming possible to build much more complete models for the winds of early-type stars. The prese…
IUE observations of eight dwarf novae : a study of the outburst cyclefrom 0.12 to 3.5 microns.
Szkody, P.
The dwarf novae are a class of close binary systems with a G-M star transferring mass to a white dwarf. The transferred material accumulates in a disk and accretes onto the white dwarf. Dwarf novae are characterized by outbursts on time scales of weeks to months possibly triggered by instabilities in the disk. To test the steady state models and t…