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Decision Trees for Automated Identification of Cosmic-Ray Hits in Hubble Space Telescope Images
Chandar, Rupali; Ford, Holland; White, Richard +2 more
We have developed several algorithms for classifying objects in astronomical images. These algorithms have been used to label stars, galaxies, cosmic rays, plate defects, and other types of objects in sky surveys and other image databases. Our primary goal has been to develop techniques that classify with high accuracy, in order to ensure that cel…
High energy cosmic-ray nuclei results on Ulysses: 2. Effects of a recurrent high-speed stream from the southern polar coronal hole
Sierks, H.; Kunow, H.; Wibberenz, G. +9 more
Since June 1992 the Kiel Electron Telescope on board ULYSSES measures 26-day variations of the order of 6% in the fluxes of high energy H and He. In May 1993 ULYSSES entered into the unipolar region of the southern polar coronal hole, but continued to observe similar effects: increases in the MeV proton channels due to acceleration near the shocks…
A Semiempirical Determination of the Wind Velocity Structure for the Hybrid-Chromosphere Star alpha Trianguli Australis
Ayres, Thomas R.; Harper, Graham M.; Bennett, Philip D. +3 more
We have used the Goddard High-Resolution Spectrograph (GHRS) on the Hubble Space Telescope to study the wind of the hybrid-chromosphere star α TrA (K4 II). The stellar wind produces significant absorption at negative radial velocities in the chromospheric Mg II resonance lines (h and k). Spectra obtained with the GHRS echelle high-resolution grati…
The Ulysses south polar pass: Energetic ion observations
Balogh, A.; Forsyth, R. J.; Goldstein, B. E. +5 more
We present here a preliminary analysis of observations of energetic ions during the first polar pass of the Ulysses spacecraft, concentrating mainly on the region where the spacecraft was continually immersed in high speed flow from the polar coronal hole. During the ascent to high latitudes, a single recurrent peak was observed once per solar rot…
HST/GHRS Observations of the Interplanetary Medium Downwind and in the Inner Solar System
Bertaux, Jean-Loup; Clarke, John T.; Lallement, Rosine +1 more
We present high dispersion spectra of the interplanetary medium (1PM) hydrogen Lyα emission along lines of sight to infinity and to Mars, obtained with the Hubble Space Telescope (HST) and Goddard High Resolution Spectrograph (GHRS) in 1991 May, including a detailed description of the data analysis procedures. The observed 1PM emission at 46° from…
Interstellar Lead
York, D. G.; Welty, D. E.; Lauroesch, J. T. +2 more
The spectrum of 1 Sco has been recorded in the region of the 1434 A line of Pb II at S/N = 220, using the ECH-A mode of the HST/GHRS. Absorption by interstellar Pb II is seen with an equivalent width W lambda = 0.3 +/- 0.2 (2 sigma ) mA, at a radial velocity which agrees satisfactorily with that of the strongest component of the interstellar Na I …
Gas near the Center of 30 Doradus As Revealed by Hubble Space Telescope Images
Lynds, Roger; Groth, Edward J.; O'Neil, Earl J., Jr. +4 more
We present images of a 40 pc region of the 30 Doradus nebula centered about 1 arcminute north of the luminous star cluster R136 in the Large Magellanic Cloud. The region was imaged with the Hubble Space Telescope Wide Field Camera through Hα, [S II], and stellar continuum filters. These data allow us to examine this region of star formation and th…
Observations of plasma waves in magnetic holes
Pick, M.; Balogh, A.; Forsyth, R. J. +5 more
We report the first observations of Langmuir waves excited within magnetic holes, which are characterized by a depression of magnetic field strength. This phenomenon is very common in the solar wind. In addition to Langmuir waves, waves at a few kHz, which are typical of Doppler-shifted ion acoustic frequencies in the solar wind, and low frequency…
Estimating the external accuracy of HIPPARCOS parallaxes by deconvolution.
Lindegren, L.
The external standard errors of a statistically homogeneous set of trigonometric parallaxes may be estimated from the distribution of small and negative parallax values. The paper describes a method using the Richardson-Lucy deconvolution algorithm combined with a fitting procedure to derive simultaneously an estimate of the distribution of true p…
Direct detection of a cometary nucleus with the Hubble Space Telescope.
Lamy, P. L.; Toth, I.
We report the unambiguous detection with the Planetary Camera of the Hubble Space Telescope of the nucleus of comet P/Faye 1991XXI during its last perihelion passage when it was at 0.6AU from the Earth. The high resolution of the HST allowed to discriminate the nucleus against the bright coma. The reduced V magnitude of the nucleus ranges between …