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Cepheid distances from blue main-sequence companions.
Bohm-Vitense, E.
The author determines the absolute visual magnitudes of main-sequence Cepheid companions from their effective temperatures. These are obtained by comparing the measured relative energy distributions with model atmosphere energy distributions. Assuming an average galactic extinction law, it is found that the distance moduli for the Cepheids should …
The unexpected ultraviolet variability of Herbig-Haro object 1.
Shull, J. M.; Brugel, E. W.; Bohm-Vitense, E. +1 more
The line fluxes of the C IV 1550 A and semiforbidden C III 1909 A emission lines in HH 1 are noted to have monotonically decreased by factors of 4-6 between 1979 and 1983, despite a lack of indications of optical range changes. The thickness of the shocked layers and preshock density can be estimated on the basis of these rapid changes, with resul…
The newly discovered eclipsing supergiant 22 Vulpeculae.
Kondo, Y.; Ake, T. B.; Parsons, S. B.
Spectra obtained with the IUE satellite have led to the discovery of a new atmospheric eclipsing binary belonging to the ζ Aurigae class of stars, 22 Vul. This system is unique in that it is the first one found with a G-type primary (G3 Ib-II), while the spectral type of the secondary is the latest (B9) and its period is the shortest (249 days) of…
The ultraviolet spectra of active galaxies with weak optical Fe II lines.
Netzer, H.; Wamsteker, W.; Wills, B. J. +1 more
The authors have obtained simultaneous optical and IUE spectra of two Seyfert galaxies that show very weak optical Fe II lines: Mrk 290 and Mrk 915. IUE archival spectra of the radio galaxy 3C 390.3 are also compared with optical data obtained during the same year. Strong, distinct ultraviolet features are observed in the spectrum of Mrk 290. A fi…
Rotational modulation of chromospheric emission in cool giants and "hybrid" stars.
Stencel, R. E.; Mullan, D. J.; Brosius, J. W.
Archival data from the International Ultraviolet Explorer have been used to study temporal variations of the Mg II h and k emission lines in eight late-type giants. Evidence is presented that the variations are periodic in nature. It is argued that the periodicities can be interpreted in terms of rotation. It is found that the four fastest rotator…
Multifrequency observations of the BL Lacertae object PKS 0537-441.
Maraschi, L.; Tanzi, E. G.; Treves, A. +1 more
PKS 0537 - 441 was repeatedly observed in the UV band with the International Ultraviolet Explorer and in the X-ray with the Einstein Observatory. On September 27, 1980, simultaneous observations in the two bands were obtained. Near-infrared photometry preceding and following the simultaneous observations by about one month is available from the li…
Ultraviolet studies of stars in the populous cluster NGC 2100 in the Large Magellanic Cloud.
Bohm-Vitense, E.; Proffitt, C.; Hodge, P.
The authors have studied the ultraviolet energy distributions of the B stars in the LMC cluster NGC 2100. The ultraviolet extinction law was studied for the LMC cluster. The Teff-luminosity diagrams were determined. The brightest stars in the clusters are evolved stars on the "horizontal" supergiant branch. No P Cygni profiles indicatin…
Two-phase ultraviolet spectrophotometry of the pulsating white dwarf ZZ Piscium.
Holm, A. V.; Bond, H. E.; Panek, R. J. +3 more
Spectra of the pulsating white dwarf ZZ Psc (= G29-38) were obtained using the International Ultraviolet Explorer. By using a multiple-exposure technique in conjunction with simultaneous ground-based exposure-metering photometry, it was possible to obtain mean on-pulse and off-pulse spectra in the 1950-1310 A wavelength range. The ratio of the tim…
Variable, optically thick plasma in the interacting binaries R Arae and HD 207739.
Kondo, Y.; Parsons, S. B.; McCluskey, G. E., Jr.
Two close binaries observed with the IUE, R Ara and HD 207739, exhibit strong variations of spectral energy distribution that indicate the presence of variable, optically thick extrastellar gas. The deepening of the secondary (eclipse-like) minimum toward shorter wavelengths observed in the ultraviolet light curves of R Ara also provides additiona…
A study of depletions within the rho Ophiuchi cloud based on IUE observations of HD 147889.
Joseph, C. L.; Snow, T. P.
Archival IUE data on the deeply embedded Rho Oph cloud star HD 147889 have been used to derive column densities for several species. The poor data quality and limited useful spectral coverage made unambiguous abundances very difficult to deduce, but firm limits could be set. Absolute depletions have been estimated, based on an assumed value of the…