Search Publications
X-ray and soft gamma-ray spectra of broad-line radio galaxies
Zdziarski, Andrzej A.; Madejski, Greg M.; Johnson, W. Neil +2 more
We study X-ray and soft gamma-ray spectral properties of nearby broad-line radio galaxies (BLRGs) using data from GingaASCA, OSSE and EXOSAT. The X-ray spectra are well fitted by an intrinsic power-law continuum with an energy index of alpha~0.7, moderately absorbed by a cold medium. In addition, the Ginga spectra show fluorescent Fe Kalpha lines …
Solar irradiances and radiances of UV and EUV lines during the minimum of sunspot activity in 1996
Wilhelm, K.; Curdt, W.; Lemaire, P. +6 more
Full Sun observations in UV and EUV emission lines were performed by SUMER (Solar Ultraviolet Measurements of Emitted Radiation) on SOHO (Solar and Heliospheric Observatory) in 1996. The radiometric pre-flight calibration of SUMER is traceable to a primary radiometric source standard - the electron storage ring BESSY. Based on this calibration, th…
Detailed study of FUV Jovian auroral features with the post-COSTAR HST faint object camera
Prangé, Renée; Rego, Daniel; Pallier, Laurent +3 more
A set of Hubble Space Telescope faint object camera images taken in the H2 bands near 1550 Å is used to infer the morphological properties of the steady state Jovian FUV aurorae. We focus on issues best addressed using the excellent spatial resolution available after correction of the spherical aberration, i.e., those related to high la…
Detection of Atomic Deuterium in the Upper Atmosphere of Mars
Krasnopolsky, Vladimir A.; Mumma, Michael J.; Randall Gladstone, G.
Photometry of Proxima Centauri and Barnard's Star Using Hubble Space Telescope Fine Guidance Sensor 3: A Search for Periodic Variations
Hemenway, P. D.; Jefferys, W. H.; Nelan, E. +10 more
We have observed Proxima Centauri and Barnard's star with the Hubble Space Telescope Fine Guidance Sensor 3. Proxima Cen exhibits small-amplitude, periodic photometric variations. Once several sources of systematic photometric error are corrected, we obtain 2 mmag internal photometric precision. We identify two distinct behavior modes over the pas…
Thermal Water Vapor Emission from Shocked Regions in Orion
Neufeld, David A.; Kaufman, Michael J.; Melnick, Gary J. +1 more
Using the Long Wavelength Spectrometer on board the Infrared Space Observatory, we have observed thermal water vapor emission from a roughly circular field of view approximately 75" in diameter centered on the Orion BN-KL region. The Fabry-Perot line strengths, line widths, and spectral line shifts observed in eight transitions between 71 and 125 …
LASCO observations of an Earth-directed coronal mass ejection on May 12, 1997
St. Cyr, O. C.; Plunkett, S. P.; Michels, D. J. +5 more
Coronal mass ejections (CMEs) that occur near the center of the solar disk are most likely to impact Earth. Detection of such events as ‘halos’ in white-light coronagraphs has been somewhat controversial in recent years. We present observations from the LASCO coronagraphs on SOHO that provide convincing evidence of the detection of an Earth-direct…
Transient Effects and Disturbed Conditions
Wibberenz, G.; Potgieter, M. S.; Bieber, J. W. +1 more
In the present phase of the solar cycle no big transients leading to strong modulation had been observed after 1991. Apart from a few minor disturbances cosmic rays were still recovering to a new intensity maximum. It was suggested, therefore, that existing literature from previous cycles should be critically reviewed. The scene was set by the int…
Solar wind radial and latitudinal structure: Electron density and core temperature from Ulysses thermal noise spectroscopy
Moncuquet, Michel; Issautier, Karine; Meyer-Vernet, Nicole +1 more
We present new in situ solar wind plasma measurements obtained during Ulysses fast transit from the south solar pole to the north one, which took place 1 year before the 1996 sunspot minimum. The data were obtained with the radio receiver of the Unified Radio and Plasma Wave Experiment, using the method of quasi-thermal noise spectroscopy, which i…
The nitrogen spectra of Wolf-Rayet stars. A grid of models and its application to the Galactic WN sample
Hamann, W. -R.; Koesterke, L.
Adopting the ``standard model'' for Wolf-Rayet atmospheres, non-LTE radiation transfer calculations are performed which account for helium and nitrogen. Grids of theoretical models are presented for the whole relevant parameter range. The WN classification criteria are employed in order to identify the subtype domains, and inconsistencies are disc…