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The Spectrum of NGC 7027
Feibelman, W. A.; Aller, L. H.; Keyes, Charles D.
IUE and echelle spectrograph observations of the planetary nebular NGC 7027 are analyzed to obtain nebular plasma diagnostics and chemical abundances. It is found that most of the nebular plasma has a density of about 60,000/cu cm and a temperature of about 14,000 K. The results suggest that the stellar radiation field is greatly enhanced shortwar…
PG 1553+11 : a bright optically selected BL Lacertae object.
Treves, Aldo; Falomo, Renato
A detailed study of the bright optically selected BL Lac object PG 1553 + 11 is presented. UV observations, obtained during a high state of the source, together with simultaneous optical spectrophotometry and near-IR photometry, allow the spectral flux distribution to be examined from 8 x 10 to the 13th to 2.5 x 10 to the 15th Hz. This distributio…
Camera Artifacts in IUE Low-Dispersion Spectra
Crenshaw, D. Michael; Norman, Dara J.; Bruegman, Otto W.
Sky-background images obtained by the International Ultraviolet Explorer (IUE) were analyzed to study artificial spectral features (camera artifacts) in low-dispersion spectra. The artifacts mimic emission features and have been present in long-exposure spectra since the launch of the IUE satellite. The camera artifacts are strong in spectra chara…
The Orbit and Colors of the Cepheid S MUSCAE
Evans, Nancy Remage
A new orbit has been computed for the binary Cepheid S Mus combining new data from Mount John Observatory with previous data. Corrections to the colors and reddening due to the light from the companion are derived. The spectral type determined from IUE low-dispersion spectra is used for these corrections. The corrections are small, even though the…
Massa's Star, HD 93840: A New Extreme BN Supergiant
Walborn, Nolan R.; Nichols-Bohlin, Joy; Fitzpatrick, Edward L.
New optical digital spectrograms of HD 93840 and several comparison objects are presented and discussed, together with IUE high-resolution data for the same stars. The optical observations confirm HD 93840 (BN1 Ib) as an extreme nitrogen-enhanced supergiant, as originally suggested by Massa (1989). The contrasts with HD 96248 (BC1.5 Iab) are espec…
HD 43246 and HD 127208: Two Unusual F-G + B Binary Systems
Parsons, Sidney B.; Fekel, Francis C.; Dempsey, Robert C. +1 more
New optical spectroscopic observations along with ultraviolet IUE observations have been obtained for the two interacting F or G III + B V binaries: HD 43246 and HD 127208. Photometric observations indicate random changes superimposed on regular ellipsoidal light variations, the latter probably the result of tidal distortion of the giant primaries…
IUE and Optical Data during the Low State of H0538+608 (BY Camelopardalis)
Szkody, Paula; Mateo, Mario; Downes, Ronald A.
IUE short- and long-wavelength spectra, CCD differential BR photometry, and a portion of a J light curve were obtained during January-March 1989 when H0538 + 608 (BY Cam) was in a low state about 3 magnitudes below its normal high-state V magnitude. The IUE short-wavelength spectrum showed that all the strong emission lines apparent at the high st…
Cepheid Companions? FM Aquilae, FN Aquilae, RX Aurigae, Y Lacertae, and RS Orionis
Evans, Nancy Remage; Szabados, Laszlo; Udalska, Joanna
IUE spectra have been used to search for companions of FN Aql and RX Aur, two classical Cepheids which have been tentatively identified as binary stars on the basis of cyclic variations in their pulsation periods. Three other Cepheids, FM Aql, Y Lac, and RS Ori, suspected of having blue companions from the (U-B), (B-V) diagram, have also been inve…
Signal-to-Noise Ratios in IUE SWP-LO Spectra of Chromospheric Emission-Line Sources
Ayres, Thomas R.
The short-wavelength-prime (SWP) detector of the International Ultraviolet Explorer should operate near the photon-counting limit, but the noise levels in flat-field images are several times higher. The exaggerated noise can be traced to the incomplete removal of the pixel-to-pixel granularity of the television frames by the prevailing spectral im…
Ultraviolet Spectra of Field Horizontal Branch A-Type Stars. II.
Adelman, Saul J.; Philip, A. G. Davis; Hayes, D. S.
The spectra of six additional A-type stars have been obtained at low resolution between 1200 and 1900 A with the IUE. The energy distributions of four of the stars match that of the field horizontal branch (FHB) distribution in Huenemoerder et al. (1984) while those of the other two do not. Three of the FHB stars fall above a line in the C(19 - V)…