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Grain Ultraviolet Extinction Properties of Recently Discovered Post--Asymptotic Giant Branch Stars
Buss, Richard H., Jr.; Lamers, Henny J. G. L. M.; Snow, Theodore P., Jr.
The circumstellar grains of two hot evolved postasymptotic giant branch stars, HD 89353 and HD 213985, are examined, deriving the extinction around 2175 A. An unsuccessful attempt to detect 6614 A diffuse band absorption arising from the grains implies that the carrier of this diffuse band is not the carrier of the unidentified IR features reporte…
The UV silicon spectra of early B stars.
Massa, D.
Equivalent widths of UV silicon lines obtained from high dispersion IUE SWP spectra for a sample of 37 mid- to early B stars are presented. These are compared to other atmospheric diagnostics and to model atmosphere calculations. It is found that some of the UV silicon lines are extremely sensitive to stellar temperature and luminosity over the ra…
X-Ray Observations of Planetary Nebulae with the EXOSAT Satellite
Apparao, Krishna M. V.; Tarafdar, S. P.
Twelve planetary nebulae have been observed with X-ray detectors in the Exosat satellite. Eight planetary nebulae are found to emit detectable X-rays, out of which four are reported here for the first time. Six of these are extended nebulae, while two are nebulae of smaller size. The detection of the six older nebulae agrees with the earlier sugge…
A Third X-Ray Spectral Mode in Scorpius X-1: Similarities to the Other Bright Bulge Sources
Hasinger, G.; Priedhorsky, W. C.; Middleditch, J.
Sco X-1 normally shows two spectral/quasi-periodic oscillation (QPO) modes. In this paper, new observations of Sco X-1 are reported which show it in a third mode which is similar to the 'horizontal branch' displayed by Cyg X-2 and suggests that the Galactic bulge sources follow a common, Z-shaped spectral pattern. In this mode, the spectral hardne…
Long- and short-term variability of the T Tauri star RY Lupi.
Liseau, R.; Gahm, G. F.; Fischerstrom, C. +1 more
Data are presented on spectroscopic and photometric observations of the T Tauri star RY Lupi carried out since 1981 from the FUV to the IR spectral region. These data show a remarkable kind of variability of the RY Lupi. Namely, the FUV and the IR fluxes, as well as the fluxes in H-alpha and H-beta are relatively constant, while the range in V mag…
The colour of Comet P/Halley's nucleus and dust
Keller, H. U.; Thomas, N.
Results are presented on the absolute calibration of the Halley Multicolor Camera (HMC), showing that HMC is 24 less sensitive than previously thought. The results are used to determine the reflectivity of the nuclear surface of the P/Halley comet, its color, and the color of the dust within 300 km of the nucleus. Results showed that the nucleus o…
Ultraviolet Spectrophotometry and Optical and Infrared Photometry of the Old Nova GK Persei
Raymond, John C.; Wu, Chi-Chao; Swank, Jean H. +3 more
IUE observations in the 1150-3250-A region were obtained of GK Per during the rise, at the maximum, and during the decline of the 2.5-mag optical outburst in 1981. The results support previous predictions for the interaction of an accretion disk with the magnetic field of an accretion star. The luminosity at minimum is found to be 2.3 solar lumino…
Active phenomena in the pre-main sequence Herbig AE star HD 163296.
Talavera, A.; Catala, C.; Simon, T. +3 more
Observations by IUE of the short-term variability of the Mg II and Ca II resonance lines in the Herbig Ae star HD 163296 are presented. Evidence that these lines show a phenomenon of rotational modulation, similar to the one observed in AB Aur, another Herbig Ae star is found. The variations in the spectrum of HD 163296 are even more conspicuous t…
Fast Winds in Central Stars of Some Planetary Nebulae
Perinotto, M.; Cerruti-Sola, M.
Winds from the central stars of the planetary nebulae NGC 1535, NGC 6210, NGC 7009, IC 418, and IC 4593 have been investigated with high-resolution IUE spectra. All these stars present P Cygni profiles in some of the following lines: N V 1240, O IV 1342, O V 1371, Si IV 1397, C IV 1549, and N IV 1719 A. These profiles have been analyzed with the S…
Effective temperatures of AP stars.
Stepien, K.; Dominiczak, R.
A new method of determination of the effective temperatures of Ap stars is suggested in which at first the temperature of a model best reproducing the observed visual energy distribution is determined and then a correction to this temperature resulting from the UV flux deficit is added. The method is calibrated on a sample of stars with energy dis…