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Three-Fluid 2.5-dimensional Magnetohydrodynamic Model of the Effective Temperature in Coronal Holes
Davila, J. M.; Ofman, L.
Recent SOHO Ultraviolet Coronagraph Spectrometer (UVCS) observations show that protons and minor ions are hot (Tp>106 K, Ti>107 K) and anisotropic in coronal holes. A possible cause of the large perpendicular motions is unresolved Alfvénic fluctuations in the solar wind. Using the three-fluid 2.5-d…
X-Ray Spectral Features from Gamma-Ray Bursts: Predictions of Progenitor Models
Fryer, Chris L.; Böttcher, Markus
We investigate the potentially observable prompt or delayed X-ray spectral features from the currently popular gamma-ray burst (GRB) models. During the evolution of many GRB progenitors, a disk around the central GRB source is produced. Shock heating as the GRB ejecta collide with the disk may produce observable X-ray features. We first summarize …
New Proplyds, Outflows, Shocks, and a Reflection Nebula in M43 and the Outer Parts of the Orion Nebula
O'Dell, C. R.
Hubble Space Telescope WFPC2 images made as planned parallel observations have produced emission-line images of fields in the outer portions of the Orion Nebula and near the center of the companion H II region, M43. Examination of these images have uncovered three new bright proplyds and one silhouette proplyd. Two of the bright proplyds lie withi…
Bright X-Ray Transients in the Andromeda Galaxy Observed with Chandra and XMM-Newton
Trudolyubov, Sergey P.; Borozdin, Konstantin N.; Priedhorsky, William C.
We study three transient X-ray sources that were bright in the central region of the M31 galaxy in the year 2000. Observations with Chandra and XMM-Newton allowed us for the first time to derive X-ray light curves of transient sources in M31 suitable for studying their variability on a timescale of months and, in some periods, weeks. The three sou…
Lead, Tin, and Germanium in the Small Magellanic Cloud Main-Sequence B Star AV 304
Proffitt, Charles R.; Sansonetti, Craig J.; Reader, Joseph
We have determined the lead, tin, and germanium abundances of the early B main-sequence star AV 304 in the Small Magellanic Cloud (SMC) by using archival STIS/HST G140M spectral data to measure the Ge IV 1229.8 Å, Sn IV 1313.5 Å, and Pb IV 1313.1 Å resonance lines. We find [Ge/H]~-1.8, [Sn/H]~-1, and [Pb/H]~-0.15. We argue that finding a nearly so…
The eclipsing bursting X-ray binary EXO 0748-676 revisited by XMM-Newton
Haberl, F.; Bonnet-Bidaud, J. M.; Ferrando, P. +2 more
The bright eclipsing and bursting low-mass X-ray binary EXO 0748-676 has been observed at several occasions by XMM-Newton during the initial calibration and performance verification (CAL/PV) phase. We present here the results obtained from observations with the EPIC cameras. Apart from several type-I X-ray bursts, the source shows a high degree of…
Coordinated observations of the quiet Sun transition region using SUMER spectra, TRACE images and MDI magnetograms
Innes, D. E.
The relationship between the transition region ultraviolet emission and the underlying magnetic field is explored through a detailed analysis of SUMER SI IV line profiles, TRACE C IV, continuum and 171 Å intensities, and MDI high resolution magnetic field measurements. The observations track a narrow area of quiet Sun near disk center over a perio…
Tomographic Separation of Composite Spectra. VII. The Physical Properties of the Massive Triple System HD 135240 (δ Circini)
Gies, Douglas R.; Kaper, L.; Fullerton, A. W. +5 more
We present the results of a radial velocity study of the massive, double-lined, O binary HD 135240 based primarily on UV spectroscopy from the International Ultraviolet Explorer. Cross-correlation methods indicate the presence of a third stationary spectral line component which indicates that the system is a triple consisting of a central 3.9 day …
Uranus' Apparent Seasonal Variability in 25 HST Filters
Karkoschka, Erich
Hubble Space Telescope (HST) images of Uranus taken in 1997 reveal that Voyager's view of the southern hemisphere was not representative of the rest of the planet. The banded structure with hemispherical asymmetry, presented in 25 filters between 0.27 and 2.03 µm wavelength, caused Uranus' full disk to darken by as much as 35% between 1985 a…
X-ray absorption in Seyfert 2 galaxies
Perola, G. C.; Fiore, F.; Guainazzi, M. +1 more
We have studied the correlation among X-ray absorption, optical reddening and nuclear dust morphology in Seyfert 2 galaxies. Two main conclusions emerge: (i) the Balmer decrement and the amount of X-ray absorption are anticorrelated over a wide range of column density, 1021<~NH<~1024cm- 2 - the cor…