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Hα Imaging with Hubble Space Telescope-NICMOS of an Elusive Damped Lyα Cloud at z=0.6
Charlton, Jane C.; Bouché, Nicolas; Bershady, Matthew A. +3 more
Despite previous intensive ground-based imaging and spectroscopic campaigns and wideband Hubble Space Telescope (HST) imaging of the z=0.927 QSO 3C 336 field, the galaxy that hosts the damped Lyα system along this line of sight has eluded detection. We present a deep narrowband Hα image of the field of this zabs=0.656 damped Lyα absorbe…
The Case against Cold, Dark Chromospheres
Kalkofen, Wolfgang
Is the solar chromosphere always hot, with relatively small temperature variations (δT/T~0.1), or is it cold most of the time, with temperature fluctuations that reach δT/T~10 at the top of the chromosphere? Or, equivalently, is the chromosphere heated continually or only for a few seconds once every 3 minutes? Two types of empirical model, one es…
Ultraviolet Coronagraph Spectrometer Observations of a High-Latitude Coronal Hole with High Oxygen Temperatures and the Next Solar Cycle Polarity
Cranmer, S. R.; Kohl, J. L.; Miralles, M. P.
We announce the resurgence of extreme ion properties in a large, high-latitude coronal hole observed above the north heliographic pole in 2001 February at solar maximum. The observations were taken with the Ultraviolet Coronagraph Spectrometer on the Solar and Heliospheric Observatory. These observations are part of an ongoing campaign to determin…
Observation of the Halo of NGC 3077 near the ``Garland'' Region Using the Hubble Space Telescope
Madore, Barry F.; Sakai, Shoko
We report the detection of upper main-sequence stars and red giant branch stars in the halo of an amorphous galaxy, NGC 3077. The observations were made using the Wide Field Planetary Camera 2 on board the Hubble Space Telescope. The red giant branch luminosity function in the I band shows a sudden discontinuity at I=24.0+/-0.1 mag. Identifying th…
EIT and SXT Observations of a Quiet-Region Filament Ejection: First Eruption, Then Reconnection
Moore, Ronald L.; Sterling, Alphonse C.; Thompson, Barbara J.
We observe a slow-onset quiet-region filament eruption with the EUV Imaging Telescope (EIT) on the Solar Heliospheric Observatory (SOHO) and the soft X-ray telescope (SXT) on Yohkoh. This event occurred on 1999 April 18 and was likely the origin of a coronal mass ejection detected by SOHO at 08:30 UT on that day. In the EIT observation, one-half o…
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 …