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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…
Anomalous extinction in the planetary nebula Abell 30.
Greenstein, J. L.
The stellar continuous energy distribution from 8000 to 1250 A in Abell 30 is quite peculiar. The observed flux can be understood if a hot central star (approximately 200,000 K) is immersed in an absorbing dust cloud which has anomalous absorption with its peak near 2470 A. The dust nebula is a strong infrared source, maintained by conversion of t…
Ionized species observed in the spectrum of the nearby white dwarf G 191-B2B.
Kondo, Y.; Bruhweiler, F. C.
High-resolution spectra of the nearby (48 pc) white dwarf G191-B2B, obtained with the International Ultraviolet Explorer, reveal sharp resonance lines of N V, C IV, and Si IV. The origin of these features is most likely linked to the white dwarf, possibly being formed in an expanding halo around the star. Interstellar lines of C II, N I, Mg II, Si…
IUE observations of two elliptical galaxies : NGC 3379 and NGC 4472.
Capaccioli, M.; Oke, J. B.; Bertola, F.
The International Ultraviolet Explorer observations of the nuclei of the elliptical galaxies NGC 3379 and NGC 4472 show that the flux drops rapidly with decreasing wavelength until about 2300 A, below which the flux increases rapidly. The hot UV component of the radiation can be approximately represented by a blackbody at 30,000 K. The spectra of …
On the relationship between coronae and mass loss in late-type stars.
Raymond, J. C.; Dupree, A. K.; Hartmann, L.
High-dispersion spectra taken with the IUE are used to examine the temperature stratification of the wind of the hybrid atmosphere star Alpha TrA (K4 II). C IV emission is shown to have a line width of 150-200 km/s, with Si III and C III exhibiting 100 km/s widths. It is suggested that the line widths reflect wind expansion, with C IV formed in an…
Concerning the Wolf-rayet and other luminous early-type stars.
Underhill, A. B.
Effective temperatures, radii, and luminosities were determined from S2/68, ANS, UBV, and uvby photometry for four B0/B1 supergiants, four O4 stars, and four WN7/WN8 stars as well as for four test stars having spectral types between B1.5 V and 09 V and five stars with known angular diameters and effective temperatures. The effective temperatures o…