Search Publications
The speeds of coronal mass ejections in the solar wind at mid heliographic latitudes: Ulysses
McComas, D. J.; Goldstein, B. E.; Bame, S. J. +3 more
Six CMEs have been detected in the Ulysses plasma observations poleward of S31°. The most striking aspect of these mid-latitude CMEs was their high speeds; the overall average speed of these CMEs was ∼ 740 km s-1, which was comparable to that of the rest of the solar wind at these latitudes. This average CME speed is much higher than av…
Boron in the extreme Population II star HD 140283 and the production of light elements in the Early Galaxy
Gilmore, G.; Gustafsson, B.; Lambert, D. L. +4 more
Using observations of the 2496.7A Bi line with the HST GHRS at a nominal resolving power of 90,000, we have found the abundance of boron of HD140283 to be logɛ_B_(=12+log(N_B_/N_H_))=0.34+/-0.20. This result is found when a significant non-LTE effect in the formation of the Bi line is taken into account. The resulting N_B_/N_Be_ ratio is about 17 …
On the neon abundance in PG 1159-type central stars on planetary nebulae.
Rauch, T.; Werner, K.
We announce the first detection and identification of a neon line in the spectra of hot central stars of planetary nebulae. It concerns the 3644A absorption line of highly ionised neon (Ne VII) in the extremely hot (T_eff_ > 100000 K) PG1159-type (i.e. hydrogen deficient) objects RXJ2117+3412, NGC246, and K 1-16. We present medium resolution sp…
Interstellar Detection of the Intersystem Line SI ii] lambda 2335 toward zeta Ophiuchi
Savage, Blair D.; Sofia, Ulysses J.; Cardelli, Jason A. +2 more
We report on the detection of the weak intersystem transistion of Si II lambda 2335 A in the sight line toward zeta Oph using the Ech-B mode (3.5 km/s resolution) of the Goddard High Resolution Spectrograph. The high-quality spectrum is characterized by an empirically measured signal-to-noise of 450, in excellent agreement with that expected from …
Hubble Space Telescope Observations of Synchrotron Jets
Sparks, W. B.; Macchetto, F.; Biretta, J. A.
The Hubble Space Telescope for the first time enables optical and UV images of jets to be obtained with spatial resolution comparable to radio interferometric techniques. Because synchrotron emission at these wavelengths is a diagnostic of particles several orders of magnitude higher in energy and correspondingly shorter in lifetime than those pro…
The Stellar Population in the Core of M15
Paresce, Francesco; de Marchi, Guido
The inner core of the globular cluster M15 within approximately 2 sec of the geometrical center has been explored with high-resolution images taken through several broad-band UV filter with the Faint Object Camera (FOC) on board the Hubble Space Telescope (HST). Approximately 210 stars in this region down to a 5 sigma detection limit of m220<…
Sulfur Dioxide in the Atmosphere of Venus. II. Modeling Results
Esposito, L. W.; Barth, C. A.; McClintock, W. E. +1 more
We have analyzed the results from the UV sounding rocket observations of Venus made on 15 September 1988 and 29 March 1991 which obtained high-resolution spectra of Venus clouds from 199 to 230 nm. The albedo of Venus in this wavelength range is dominated by absorption features of sulfur dioxide and sulfur monoxide. We estimate that the mixing rat…
On the nickel abundance in hot hydrogen-rich white dwarfs.
Werner, K.; Dreizler, S.
We present a non-LTE iron and nickel abundance analysis of four hot hydrogen rich white dwarfs from high resolution IUE spectra. The investigation aims at the determination of the Ni/Fe ratio in order to investigate if radiative acceleration prevents gravitational settling of both elements. We succeeded in the first identification of nickel lines …
Spectroscopic, Orbital, and Physical Properties of the Binary Feige 24 and Detection of Transient He II Absorption in the System
Thorstensen, J. R.; Vennes, S.
We have obtained new high-dispersion optical spectroscopy at Kitt Peak National Observatory (KPNO) and new International Ultraviolet Explorer (IUE) spectroscopy of the white dwarf+red dwarf binary system Feige 24. The optical range shows a composite DA+dM spectrum, together with H I Balmer and He I emission. The orbital phase dependence of the emi…
Variable Extinction in HD 45677 and the Evolution of Dust Grains in Pre--Main-Sequence Disks
Sitko, Michael L.; Halbedel, Elaine M.; Lawrence, Geoffrey F. +2 more
Changes in the UV extinction and IR emission were sought in the Herbig Ae/Be star candidate HD 45677 (= FS CMa) by comparing UV, optical, and IR observations made approximately 10 yr apart. HD 45677 varied significantly, becoming more than 50% brighter in the UV and optical than it was a decade ago. A comparison of the observations between epochs …