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Stellar Variability in the Central Populations of 47 Tucanae from WF/PC Observations with the Hubble Space Telescope. I. Project Overview, Reduction Techniques, and First Results
Gilliland, Ronald L.; Saha, Abhijit; Shara, Michael M. +2 more
Stars in the central region of the dense globular cluster 47 Tucanae were monitored for variability using time-resolved photometry from 99 Hubble Space Telescope Planetary Camera exposures of 1000 s in the F336W (U) filter. The observations were obtained while 47 Tuc was in the continuous viewing zone (CVZ) of HST. This data set provides an unpara…
The low radio frequency limit of solar type III bursts: Ulysses observations in and out of the ecliptic
Hoang, S.; Leblanc, Y.; Dulk, G. A.
We measure the low frequency limit flo of 1028 type III bursts and compare it with the observed plasma frequency at the spacecraft fp. We consider three periods: when Ulysses was in the ecliptic plane near the Sun, far from the Sun, and out of the ecliptic; the average plasma frequency was 20, 10, and 5 kHz respectively. The …
A Study of the Chromospherically Active, Short-Period Binary VZ PISCIUM
Lu, Wenxian; Guinan, Edward F.; Hrivnak, Bruce J.
The short-period binary VZ Piscium is unusual in that it has a high space velocity, indicating that it is old, and a high mass ratio, suggesting that it is presently evolving into contact with little mass exchange having occurred between the components. In this study, we obtained lUE and visible spectra to investigate Mg II h + k and Ca II H and K…
Abundances of ammonia and carbon disulfide in the Jovian stratosphere following the impact of comet Shoemaker-Levy 9
Edgington, S. G.; Atreya, S. K.; Trafton, L. M. +3 more
Radiative transfer-scattering models were used to fit the Hubble Space Telescope UV spectroscopic observations of Jupiter taken 2.5 hours after the impact of fragment G of comet P/Shoemaker-Levy 9. They yield abundances for NH3 and CS2 of (0.25-1.3) × 1016cm-2 and (0.43-1.1) × 1015cm-2
Interpretation of Anomalous Ultraviolet Transitions of Fe II Observed in Laboratory Fourier Transform Spectra and Stellar HST and IUE Spectra
Johansson, Sveneric; Wahlgren, Glenn M.; Brage, Tomas +2 more
We discuss LS-forbidden ΔS = 2 transitions of Fe II that appear as strong lines in ultraviolet stellar and laboratory spectra. The lines occur because of indirect level mixing-two close energy levels, W2P3/2 and x6P3/2, are mixed through a third level acting as a catalyst. In transition multiplets, that …
Transition Probabilities for the UV0.01 Multiplet in N III
Judge, Philip G.; Brage, Tomas; Fischer, Charlotte Froese
We report on large-scale ab initio multiconfiguration Hartree-Fock calculations for the UV0.01 multiplet, 2s22p2PJ - 2s2p2 4PJ prime, in N III. The resulting transition probabilities agree very well with recent semiempirical calculations, and the lifetimes for two of the three upper levels agr…
The EUVE and IUE Spectra of the Hot DA White Dwarf GD 659
Barstow, M. A.; Bruhweiler, F. C.; Sion, E. M. +1 more
We present recent EUVE spectra and new co-added lUE echelle spectra of the hot DA white dwarf GD 659. Our EUVE spectra show the expected continuum of a pure H DA white dwarf, from which we derive upper limits on the photospheric abundances for He, C, N, O, and Si. Our co-added lUE echelle spectrum shows, in addition to the common interstellar line…
Interplanetary discontinuities and Alfvén waves
Tsurutani, Bruce T.; Goldstein, Bruce E.; Neugebauer, Marcia +6 more
The rate of occurrence of interplanetary discontinuities (ROID) is examined using Ulysses magnetic field and plasma data from 1 to 5 AU radial distance from the Sun and at high heliospheric latitudes. It is found that there are two regions in interplanetary space where the ROID is high: in stream-stream interaction regions and in Alfvén wave train…
An intercomparison of plasma turbulence at three comets: Grigg-Skjellerup, Giacobini-Zinner, and Halley
Glassmeier, K. -H.; Neubauer, F. M.; Tsurutani, Bruce T.
We examine and intercompare the LF plasma wave turbulence at three comets: Grigg-Skjellerup (GS), Giacobini-Zinner (GZ), and Halley (H). All three have power spectral peaks at the local ion cyclotron frequency (the pump wave) at ∼10-2 Hz, and a power-law fall-off at higher frequencies that suggest the development of turbulent cascades […
The Circumstellar Nature of the Metallic Features in a Hot DA White Dwarf
Andersen, J.; Bruhweiler, F. C.; Holberg, J. B.
A new co-added IUE echelle spectrum of the bright DA white dwarf CD -38 deg 10980, together with a newly determined radial velocity for this star, indicate that the sharp lined Si and C absorption features seen in the UV are clearly circumstellar in origin. Absorption in both excited and ground state transitions occurs at a velocity displaced by -…