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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 …
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…
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 …
A Combined Hipparcos and Multichannel Astrometric Photometer Study of the Proposed Planetary System of ρ Coronae Borealis
Han, Inwoo; Gatewood, George; Black, David C.
Hipparcos and Multichannel Astrometric Photometer (MAP) observations of ρ Coronae Borealis independently display astrometric motion at the period of the proposed ``extrasolar planetary'' companion to the star. Individual least-squares fits to each astrometric data set yield independent estimates of the semimajor axis, inclination, and node angle t…
The Distance of the Large Magellanic Cloud Cluster NGC 1866
Walker, A. R.; Hill, V.; Castellani, V. +3 more
Hubble Space Telescope V, I photometry of stars in the Large Magellanic Cloud cluster NGC 1866 shows a well-defined cluster main sequence (MS) down to V=25 mag, with little contamination from field or foreground stars. We use the MS fitting procedure to link the distance of NGC 1866 to the Hipparcos determination of the distance for the Hyades MS …
Identification of Fe II Emission Lines in FUSE Stellar Spectra
Harper, Graham M.; Brown, Alexander; Linsky, Jeffrey L. +2 more
We identify two complexes of Fe II emission lines in far-ultraviolet spectra of the stars α TrA and HD 104237. Using spectra from both the Far Ultraviolet Spectroscopic Explorer (FUSE) and the Space Telescope Imaging Spectrograph (STIS) on board the Hubble Space Telescope (HST), we show that these emission lines, which represent the majority of pr…
Multifrequency Analysis of the New Wide-Separation Gravitational Lens Candidate RX J0921+4529
Peng, C. Y.; Keeton, C. R.; Kochanek, C. S. +9 more
We report the discovery of a new two-image gravitational lens candidate. The system RX J0921+4529 contains two zs=1.66 quasars separated by 6.93" with an H-band magnitude difference of Δm=1.39. The HST NIC2 H-band images reveal an H=18.2 spiral galaxy between the quasar images, which is probably a member of a zl=0.32 X-ray cl…
Chandra Detection of X-Ray Absorption Associated with a Damped Lyα System
Elvis, Martin; Bechtold, Jill; Siemiginowska, Aneta +2 more
We have observed three quasars, PKS 1127-145, Q1331+171, and Q0054+144, with the ACIS-S aboard the Chandra X-Ray Observatory in order to measure soft X-ray absorption associated with intervening 21 cm and damped Lyα absorbers. For PKS 1127-145, we detect absorption that, if associated with an intervening zabs=0.312 absorber, implies a m…