Search Publications
Variation of Thermal Structure with Height of a Solar Active Region Derived from SOHO CDS and YOHKOH BCS Observations
Antiochos, Spiro K.; Watanabe, Tetsuya; Sterling, Alphonse C. +2 more
We present observations of NOAA solar Active Region 7999 when it was near the west solar limb on 1996 December 2 and 3, using data from the Coronal Diagnostic Spectrometer (CDS) experiment on the SOHO satellite. Ratios of intensities of 2 MK material (as observed in CDS Fe XVI images) to 1 MK material (from CDS Mg IX images) indicate that there is…
Spatially Resolved Hopkins Ultraviolet Telescope Spectra of NGC 1068
Kriss, Gerard A.; Espey, Brian R.; Grimes, John P.
We present spatially resolved far-ultraviolet spectra (912-1840 Å) of NGC 1068 obtained using the Hopkins Ultraviolet Telescope (HUT) during the 1995 March Astro-2 mission. Three spectra of this prototypical Seyfert 2 galaxy were obtained through a 12" diameter aperture centered on different locations near the nucleus. The first pointing (A1) was …
First Observations of an R Coronae Borealis Star with the Space Telescope Imaging Spectrograph: RY Sagittarii near Maximum Light
Woitke, P.; Clayton, Geoffrey C.; Asplund, Martin +3 more
We describe the far-UV (1140-1740 Å) spectrum of the hydrogen-deficient R Coronae Borealis (RCB) star RY Sgr, obtained near maximum light (pulsational phase ~0.1) by the Space Telescope Imaging Spectrograph (STIS) on Hubble Space Telescope. The far-UV spectrum shows a photospheric continuum rising steeply toward longer wavelengths and two prominen…
Interacting and Interplanetary Protons Accelerated on Diverging Magnetic Field Lines: Stochastic Acceleration
Laitinen, T.; Torsti, J.; Mäkelä, P. +2 more
We study the ratio of the numbers of interplanetary to interacting protons, Γ, using a model of stochastic acceleration on open magnetic field lines in solar corona. The impact of diverging coronal magnetic field lines is incorporated into the particle transport operator and shown to be unavoidable, no matter how small the mean free path may be. W…
Hubble Space Telescope Faint Object Spectrograph Observations of a Unique Grouping of Five QSOs: The Sizes and Shapes of Low-z Lyα Forest Absorbers
Turnshek, David A.; Monier, Eric M.; Hazard, Cyril
Observations of QSO pairs suggest that the structures responsible for Lyα forest absorption lines must have radii of hundreds of kiloparsecs if they are spherical or disklike in shape. However, only observations of groups of three or more QSOs closely spaced on the sky provide a way to measure their transverse sizes/characteristic clustering lengt…
Hubble Space Telescope NICMOS Observations of Rest-Frame Optical Continuum and Hα+[N I] Emission In FSC 10214+4724
Armus, L.; Scoville, N. Z.; Soifer, B. T. +4 more
High-resolution 1.10, 2.05, 2.12, and 2.15 µm imaging of the gravitationally lensed system FSC 10214+4724 are presented. These data extend Hubble Space Telescope (HST) observations of the lens system to redder wavelengths, thus providing the highest resolution images to date of the rest-frame optical and narrow-line (i.e., Hα+[N II]) regions…
Absorption/Emission of Solar p-Modes: Michelson Doppler Interferometer/SOHO Observations
Zweibel, Ellen G.; Jain, Rekha; Haber, Deborah
We search for sources and sinks of solar p-mode waves by creating absorption maps from Dopplergrams taken by the Michelson Doppler Interferometer instrument on board SOHO. Although the maps are noisy, we present evidence for sources and sinks, of duration ~0.5-1 hour or less, based on an autocorrelation analysis of maps made from sequential interv…
Distances to the High Galactic Latitude Molecular Clouds G192-67 and MBM 23-24
Burrows, David N.; Grant, Catherine E.
We report on distance determinations for two high-Galactic latitude cloud complexes, G192-67 and MBM 23-24. No distance determination exists in the literature for either cloud. Thirty-four early-type stars were observed toward the two clouds, more than half of which have parallaxes measured by the Hipparcos satellite. For the remaining stars, we h…
An Analytic Description of Coronal Proton Trapping
Kocharov, Leon; Torsti, Jarmo; Kovaltsov, Gennadi A.
Analytic steady state solutions of the focused diffusion equation are used to deduce proton trapping time, τtrap, an average residence time for all particles injected into the magnetic loop. We take into account the effect of magnetohydrodynamic (MHD) turbulence and the divergence of magnetic field lines in both the corona and chromosph…
Compact Nuclei in Galaxies at Moderate Redshift. II. Their Nature and Implications for the Active Galactic Nucleus Luminosity Function
Green, Richard F.; Griffiths, Richard E.; Ratnatunga, Kavan +1 more
This study explores the space density and properties of active galaxies to z~=0.8. We have investigated the frequency and nature of unresolved nuclei in galaxies at moderate redshift as indicators of nuclear activity such as active galactic nuclei (AGNs) or starbursts. Candidates are selected by fitting imaged galaxies with multicomponent models u…