Search Publications
Nonthermal Flare Emission from MEV-Energy Electrons at 17, 34, and 86 GHZ
Kundu, M. R.; White, S. M.; Shibasaki, K. +1 more
We present analyses of two solar flares observed with high spatial resolution at 86 GHz with the BIMA millimeter-wavelength telescope and at 17 and 34 GHz with the Nobeyama radioheliograph. The flares were observed on 1998 November 24 and 1999 May 1. At millimeter wavelengths these are impulsive events, and therefore they must be produced by MeV-e…
Hubble Space Telescope Planetary Camera Imaging of HH 29
Bally, John; Morse, Jon; Devine, David +2 more
We present Hubble Space Telescope Hα and [S II] images of HH 29. The proximity of HH 29 (140 pc) and the high resolution of the Planetary Camera has resulted in the most detailed images obtained so far of any Herbig-Haro object. The most prominent feature is a linear Hα ridge leading the working surface of a bow shock with a chaotic trailing [S II…
Influence of Turbulent Energy Spectra on Damping and Frequency Reduction of the Solar F-Mode
Murawski, K.; Mędrek, M.
This paper generalizes the random wave theory that was developed to explain the recently observed line width spreading and frequency reduction of the f-mode. The generalization is based on a replacement of the Gaussian energy spectrum by a more realistic spectrum such as von Karman, Reynolds, or exponential as well as on an averaging of the result…
Preconditioning the Differential Emission Measure (Te) Inverse Problem
Brown, J. C.; Charbonneau, P.; McIntosh, S. W.
In an inverse problem of any kind, poor conditioning of the inverse operator decreases the numerical stability of any unregularized solution in the presence of data noise. In this paper we show that the numerical stability of the differential emission measure (DEM) inverse problem can be considerably improved by judicious choice of the integral op…
Trapping and Precipitation of Protons during Stochastic Acceleration in Magnetic Loops
Torsti, J.; Kocharov, L.; Kovaltsov, G. A.
We study confinement of particles during the stochastic acceleration in coronal magnetic loops. Analytic solutions and Monte Carlo simulations of the coordinate-dependent focused-diffusion transport and acceleration are employed to deduce the effective leaky-box escape time, τesc. The rigorously correct expression of the escape time yie…
71 Tauri: Hyades Enigma Resolved?
Ayres, Thomas R.; Simon, Theodore
71 Tauri (HD 28052; F0 IV-V) is an enigmatic object for two reasons: (1) it is the second brightest X-ray source in the Hyades, yet early F stars as a rule are not strong coronal emitters; and (2) it lies a magnitude above the cluster main sequence, but radial velocity studies and speckle imaging suggest that it is single. Recently, long-slit ultr…
On the Correlation between CO Absorption and Far-Ultraviolet Nonlinear Extinction toward Galactic OB Stars
Feldman, Paul D.; Andersson, B. -G.; Burgh, Eric B. +1 more
A sample of 59 sight lines to reddened Galactic OB stars was examined for correlations of the strength of the CO Fourth Positive (A1Π-X1Σ+) absorption band system with the ultraviolet interstellar extinction curve parameters. We used archival high-dispersion NEWSIPS IUE spectra to measure the CO absorption for comp…
In-Flight Calibration of the ROSAT HRI Ultraviolet Sensitivity
Micela, G.; Murray, S. S.; Barbera, M. +2 more
Comparing measured and estimated count rates of a few selected sample stars, we confirm the validity and provide the in-flight calibration of the ROSAT HRI UV/visible effective area model in Zombeck et al. The count rate estimates for Betelgeuse derived with this model are in agreement with the measured HRI upper limit. This result is also confirm…
Limits on the Spatial Extent of Active Galactic Nuclei Measured with the Fine Guidance Sensors of the Hubble Space Telescope
Hook, Richard N.; Miley, George; Schreier, Ethan J.
The optical structures of several active galactic nuclei (AGNs) have been studied using the fine guidance sensors (FGSs) on the Hubble Space Telescope (HST). The FGSs are interferometric devices that can resolve structure on scales of 20 mas or less and hence have the potential to improve on the resolution attainable by HST's cameras. The FGSs pro…
Multiple Scattering of Hydrogen Lyα Radiation in the Coma of Comet Hyakutake (C/1996 B2)
Keller, H. U.; Combi, M. R.; Meier, R. R. +1 more
The Goddard High Resolution Spectrograph on board the Hubble Space Telescope measured hydrogen Lyα (H Lyα) line profiles at different locations around the coma of comet Hyakutake (C/1996 B2) in 1996 April. The spectral resolution of about 4 km s-1 (Doppler velocity, FWHM) was significantly better (by a factor of 2-3) than any previous m…