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SOHO/SWAN Observations of the Structure and Evolution of the Hydrogen Lyman-α Coma of Comet Hale-Bopp (1995 O1)
Quemerais, E.; Bertaux, J. -L.; Combi, M. R. +2 more
The SWAN all-sky camera on the SOHO spacecraft observed the hydrogen Lyman-alpha coma of Comet Hale-Bopp (1995 O1) from January through May 1997. The observations covered heliocentric distances from 1.75 AU before perihelion to 1.29 AU after, showing the hydrogen coma to vary in brightness, shape, and orientation with the comet's orbital position.…
A strategy for finding gravitationally lensed distant supernovae
Ellis, Richard; Smail, Ian; Madau, Piero +2 more
Distant Type Ia and II supernovae (SNe) can serve as valuable probes of the history of the cosmic expansion and star formation, and provide important information on their progenitor models. At present, however, there are few observational constraints on the abundance of SNe at high redshifts. A major science driver for the Next Generation Space Te…
Prompt Optical Observations of Gamma-Ray Bursts
Hurley, Kevin; McKay, Tim; Kehoe, Robert +18 more
The Robotic Optical Transient Search Experiment (ROTSE) seeks to measure simultaneous and early afterglow optical emission from gamma-ray bursts (GRBs). A search for optical counterparts to six GRBs with localization errors of 1 deg2 or better produced no detections. The earliest limiting sensitivity is mROTSE>13.1 at 10.8…
ISO observations of the reflection nebula Ced 201: evolution of carbonaceous dust
Lequeux, J.; Cesarsky, D.; Gérin, M. +1 more
We present spectrophotometric imaging mid-IR observations of the reflection nebula Ced 201. Ced 201 is a part of a molecular cloud illuminated by a B9.5V star moving through it at more than 12 km s-1. The spectra of Ced 201 give evidence for transformation of very small carbonaceous grains into the carriers of the Aromatic Infrared Band…
Cyclotron resonance in coronal holes: 3. A five-beam turbulence-driven model
Hollweg, Joseph V.
Following Hollweg and Johnson [1988], Isenberg [1990], and Li et al. [1999a], we postulate that the Sun launches a flux of low-frequency Alfvén waves, which dissipate via a turbulent cascade to high frequencies where the energy is absorbed by ion cyclotron resonant interactions. The plasma consists of two proton beams, which are proxies for the re…
The Structure of the Virgo Cluster from Surface Brightness Fluctuations in Hubble Space Telescope Images
Tsvetanov, Zlatan I.; Neilsen, Eric H., Jr.
Surface brightness fluctuations (SBF) in Hubble Space Telescope (HST) Wide Field Planetary Camera 2 images of elliptical galaxies provide the precision necessary to examine the internal structure of the Virgo galaxy cluster. In a sample of 15 elliptical galaxies with observations from the HST archive, we find that most galaxies are within 2 Mpc of…
HST/STIS Echelle Spectra of the dM1e Star AU Microscopii Outside of Flares
Robinson, Richard D.; Woodgate, Bruce; Linsky, Jeffrey L. +3 more
We report on observations of the dM1e flare star AU Microscopii obtained with the Space Telescope Imaging Spectrograph (STIS) on 1998 September 6. A total of 10,105 s of observations were obtained with the medium-resolution E140M grating. We report here on the 9200 s of ``quiescent'' data when the star did not obviously flare. In this data set, we…
Understanding CMEs and their source regions
Webb, D. F.
CMEs are an important aspect of coronal and interplanetary dynamics. They can eject large amounts of mass and magnetic fields into the heliosphere which can drive large geomagnetic storms and interplanetary shocks, a key source of solar energetic particles. However, our knowledge of the origins and early development of CMEs at the Sun is limited. …
Analysis of asymmetric p-mode profiles in GOLF data
García, R. A.; Turck-Chièze, S.; Ulrich, R. K. +8 more
We show here evidence for the necessity of an asymmetric form in modelling the profile of an acoustic mode in the power spectral density. The analysis was performed on a 805-day series of GOLF data (l=0 to 3). The assumptions used for the fits are discussed and their consequences quantified, in particular for the optimum choice of the fitting spec…
Long-Period Oscillations in Polar Plumes as Observed by cds on Soho
Doyle, J. G.; Banerjee, D.; O'Shea, E.
We examine spectral time series of the transition region line O v 629Å, observed with the Coronal Diagnostic Spectrometer (CDS) on the SOHO spacecraft in July 1997. Both Fourier and wavelet transforms have been applied independently to the analysis of plume oscillations in order to find the most reliable periods. The wavelet analysis allows us to …