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The Ultraviolet Spectrum of an Oxygen-rich Supernova Remnant in the Small Magellanic Cloud
Blair, William P.; Raymond, John C.; Danziger, John +1 more
We present ultraviolet and optical spectral data for the oxygen-rich supernova remnant 1E 0102-7219 in the Small Magellanic Cloud. The ultraviolet data were obtained with the IUE satellite and are the first data to seriously constrain the ultraviolet emission from an oxygen-rich remnant. Emission lines of O I, [O II], O III], O IV], C III], C IV, …
The Nebular Phase of Nova GQ MUSCAE 1983: Evolution of the Ionization of the Optical Spectrum
Williams, Robert E.; Krautter, Joachim
Spectroscopic observations of Nova GQ Muscae 1983 over a period of 4 years during its nebular stage reveal a steady increase in the ionization of the ejected envelope. The forbidden Fe x 6374 A coronal line first appears in the spectrum more than 2 years after maximum, and by the end of the fourth year has become the strongest line in the spectrum…
A Compact Planetary Nebula around the Hot White Dwarf EGB 6/PG 0950+139
Bond, Howard E.; Wesemael, F.; Holberg, J. B. +4 more
The remarkable central star (0950 + 139), a very hot DA/DAO white dwarf, of the planetary nebula EGB 6 is described. Follow-up observations relevant to the analyses of both the nebula and the stellar photosphere are presented. Three kinds of scenarios are discussed to account for the existence of this peculiar nebula, but none appears very promisi…
Ultraviolet Spectroscopy of Pre--Main-Sequence Accretion Disks
Kenyon, S. J.; Cassatella, A.; Hartmann, L. +1 more
Low-resolution, ultraviolet spectra of the pre-main-sequence objects Z Canis Majoris, V1057 Cygni, and FU Orionis are presented. Ultraviolet absorption features indicate spectral types of A5 I for FU Ori and F5 I for Z CMa. These results are in reasonable agreement with predictions of simple accretion disk models. The lack of significant veiling o…
EXOSAT observations of five luminous globular cluster X-ray sources.
Stella, L.; Parmar, A. N.; Giommi, P.
Exosat observations are used to search for orbital modulations in the X-ray light curves of five luminous globular cluster X-ray sources in NGC 1851, NGC 6441, NGC 6712, Terzan 1, and Terzan 2. Upper limits to possible short-period orbital modulation are presented. Two or three intensity dips are observed in the light curve of NGC 6441. The result…
Probable detection of organic-dust-borne aromatic C3H3+ ions in the coma of comet Halley
Anderson, K. A.; Reme, H.; Korth, A. +9 more
The heavy-ion analyser PICCA1,2 on the Giotto spacecraft was used to determine the composition and energy distribution of positively charged ions in the coma of comet Halley. Here we argue that the distinct peak observed at mass 39 AMU is due to the aromatic cation C3H3+ (cyclopropenyl). Laboratory mass …
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…