Search Publications
Ultraviolet Extinction Differences within NGC 6530
Bohm-Vitense, Erika; Boggs, Don
Ultraviolet extinction curves are presented for 14 stars in the very young cluster NGC 6530. The variation of the short-wavelength extinction is consistent with that expected based on random errors alone, although the weakest extinction is found only toward the cluster center. Variations significantly larger than the measurement uncertainty are fo…
On the Possible Detection of Organic Dust-borne C 3H + Ions in the Coma of Comet Halley
Reme, H.; Korth, A.; Lin, R. P. +4 more
The heavy ion analyzer (PICCA) on board the Giotto spacecraft was used to determine the composition of positively charged ions in the environment of Comet Halley. Here it is argued that a distinct peak at 37 amu, observed in the mass spectrum inside the ionopause, is due to C3H(+). It is further argued that the dominant source of this ion, as well…
IUE Observations of Wolf-Rayet Binary Systems in the Small Magellanic Cloud
Moffat, Anthony F. J.; Koenigsberger, Gloria; Auer, Lawrence H.
The results of IUE observations of three SMC W-R binary systems at various orbital phases are presented. Selective atmospheric eclipse effects are evident in HD 5980 (WN 4 + O7 I:) and Sk 188 (W04 + O4 V), and are very weak or absent in Sk 108 (WN 3 + O6.5 I:). The difference in heavy-metal content between the SMC and Galactic objects is especiall…
EXOSAT Observations of the Kepler Supernova Remnant
Arnaud, M.; Ballet, J.; Rocchia, R. +3 more
The medium-energy experiment on board Exosat was used to measure the X-ray spectrum of the Kepler supernova remnant over the range 1.5-10 keV. An Fe emission line was clearly resolved with an energy of about 6.5 keV and equivalent width of about 1.8 keV. This was superposed on a continuum with a temperature of 5.0(+3.8, -1.9) keV. The medium-energ…
Detection of a Strong Excess Noise Component in the Low State of 4U 1705-44
Hasinger, G.; Truemper, J.; Langmeier, A.
The timing analysis of four Exosat observations of the bright Galactic burst source 4U 1705-44 is presented. A correlation is found between the aperiodic noise components and the spectral variability. 4U 1705-44 shows in its low-intensity state a strong variability of the X-ray flux in the frequency range 1-64 Hz, corresponding to an rms modulatio…
Discovery of a Cool Expanding Shell at -1200 Kilometers per Second around V471 Tauri
Sion, Edward M.; Bruhweiler, Fred C.; Mullan, Dermott +1 more
High-resolution IUE spectra of V471 Tauri reveal the presence of a very-high-velocity cool expanding gas in the line of sight to the binary system with an expansion velocity of -1200 km/s. The summed strength of the coadded absorption is 125 mA + or - 25 mA, with FWHM = 30 km/s. It is suggested that the observed absorption may be related to the na…
The First UV Spectrum of Triton: IUE Observations from 2600 to 3200 Angstrom
Skinner, T. E.; Stern, S. Alan; Trafton, L. M. +2 more
The results of the first observations of Triton's spectrum below 3300 A are reported. Triton's 2700 A geometric albedo is found to be 0.28 + or - 0.04. The albedo increases monotonically from 2600 to 3200 A, with a slope of 0.13 + or - 0.03 per 1000 A. This positive slope is qualitatively similar to, but shallower than, Triton's visible albedo slo…
Highly Ionized Species and Circumstellar Shells in B8--A1 Stars
Grady, C. A.; Bruhweiler, Frederick C.; Chiu, Weihsuen A.
The nature of the C IV and Si IV absorption seen in the spectra of apparently normal late-type B and early-type A stars located within 200 pc of the sun was investigated by examining a total of 93 archival IUE spectra of 41 stars. In three of these objects, variable or asymmetric C IV profiles indicate that the absorption features have a stellar o…
The Ionization Structure of Planetary Nebulae. IX. NGC 1535
Barker, Timothy
The ionization structure of planetary nebula NGC 1535 was investigated using spectrophotometric observations of emission-line intensities over the spectral range 1400-7200 A, which were carried out in five positions in this nebula. The results obtained on the ionic abundances of He, O, N, Ne, C, and Ar in NGC 1535 suggest that it is a planetary ne…
The Chromosphere of Beta Cassiopeiae
Teays, Terry J.; Schmidt, Edward G.; Fracassini, Massimo +1 more
High-resolution, long-wavelength IUE observations and ground-based photometry of the Delta Scuti star Beta Cas is reported. The ground-based observations were used together with previous results of Antonello et al. (1986) to ensure that the IUE observations were correctly phased relative to the photometric variation. Fluxes for the emission core o…