Search Publications
Statistical Confirmation of the Ultraviolet Spectral Classification System Based on IUE Low-Dispersion Stellar Spectra
Heck, A.; Egret, D.; Nobelis, Ph. +1 more
In theIUE Low-Dispersion Spectra Reference Atlas (Hecket al., 1984a), a new spectral classification system specific to the UV had to be introduced because of the lack of one-to-one correspondence between the UV and visible ranges. It was elaborated from a classical morphological approach (Jaschek and Jaschek, 1984). This paper presents an independ…
The X-ray spectrum and variability of Markarian 421.
McHardy, I.; Warwick, R. S.; George, I. M. +1 more
The X-ray bright BL Lac object Markarian 421 (Mrk 421) was observed by Exosat four times over a period of 6 days in February 1984. The source exhibited a very soft power-law X-ray spectrum (photon spectral index is about 2.8) with an extremely low intrinsic column density (less than or equal to 10 to the 20th/sq cm). Significant X-ray variability …
Colors of Reflection Nebulae. III. Ultraviolet Scattering by Small Particles in Reflection Nebulae Associated with 17, 20, and 23 Tauri
Bohlin, R. C.; Witt, A. N.; Stecher, T. P.
New surface brightness measurements in the reflection nebulae associated with the Pleiades stars 17, 20, and 23 Tau have been carried out with the IUE satellite. Each nebula was observed at two angular offsets south of the respective illuminating star. At the larger offsets (40, 40, and 60 arcsec respectively) each nebula exhibits a flux distribut…
Simultaneous X-ray and optical monitoring of the flare star YZ CMi.
Doyle, J. G.; Rodono, M.; Butler, C. J. +1 more
Broad-band photometric observations of YZ CMi show a 1.2 mag U-band flare, however, simultaneous X-ray observations from EXOSAT show no detectable increase. It is suggested that the event could have occurred low down in a part of the chromosphere, which may not have been coupled to the transition region and corona via magnetic fields. However, a m…
Ultraviolet Spectrum and Probable Chemical Composition of the High-Excitation Planetary Nebula M1-1
Feibelman, Walter A.; Aller, Lawrence H.; Keyes, Charles D.
One of the highest excitation planetary nebulae known, M1-1, was studied with the image-tube scanner on the Shane 3-m telescope at Lick Observatory and with the International Ultraviolet Explorer. Large fractions of abundant elements such as C, N, O, S, and Ar exist in unobservable stages of ionization. Hence, it is difficult to establish the chem…
Possible effects of organelle charge and density on cell metabolism
Keenan, F. P.; Bates, B.; Catney, M. G.
To respond to gravity a biological system must: First, perceive the stimulus; and, second transduce the stimulus into an appropriate response. This laboratory has studied a system of perception and transduction involving the gravity-induced asymmetric distribution of a plant growth hormone. From these studies we have developed a working theory whi…
Coordinated EXOSAT and Optical Observations of HD 36705
White, N. E.; Collier Cameron, A.; Bedford, D. K. +3 more
EXOSAT and Einstein X-Ray Observations of the SNR 1E 1149.4-6209 in Crux: A Unified Picture?
Caraveo, P. A.; Bignami, G. F.; Mereghetti, S. +2 more
New EXOSAT and Einstein Observatory X-ray data from a region in Crux (α ≈ 11h45m, δ ≈ 62°) are reported. Morphological as well as rough spectral analysis of a large (≡1°) diffuse feature is performed. The diffuse emission is identified with a SNR, a conclusion supported by comparison with existing radio and optical data. The …
The interstellar carbon abundance. II. Rho Ophiuchi and beta Scorpii.
York, D. G.; Welty, D. E.; Hobbs, L. M.
The authors describe a procedure designed to obtain increased sensitivity from high-dispersion IUE spectra by using a flat-field spectrum to remove nonrandom noise due to the response pattern of the SEC vidicon detector. Application of this procedure to spectra of ρ Oph and β1Sco near the spin-forbidden interstellar λ2325 line of C II y…
Far UV variability of theta CrB in 1980-1985. II. Evidence for variability patterns and ionization dependence.
Stalio, R.; Doazan, V.; Thomas, R. N. +1 more
Far UV observations of Theta CrB obtained in 1980-1985 with the IUE are presented which provide evidence for long-term variability patterns associating the shape, velocity and strength of the Si IV, Al III, and Fe III lines. A differential variable behavior between lines arising from different ionization levels is also noted. The present results a…