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Optical spectra of ζ Aurigae systems. VIII. The chromosphere of HR6902.
Schroeder, K. -P.; Griffin, R. E. M.; Marshall, K. P.
We analyze chromospheric spectra of the ζ Aur system HR6902 observed during its 1987 and 1989 eclipses, deriving empirical column densities, number densities and ionization characteristics for 5 distinct heights within the giant primary's chromosphere. Column densities for CaII are determined from K-line profiles and for other ions by a curve-of-g…
The Iron Abundance of IOTA Herculis
Grigsby, James A.; Mulliss, Christopher L.; Baer, Gretchen M.
We have obtained coadded, high-resolution IUE spectra of Iota Herculis (B3 IV) in both the short-wavelength (SWP) and long-wavelength (LWP) regions. LTE synthetic spectra with a resolution identical to that of IUE were produced with the Kurucz model atmosphere and spectral synthesis codes ATLAS9/SYNTHE. Model parameters were chosen from the litera…
Probable detection of high-energy gamma-ray emission from OJ 287 during a major optical flare.
Shrader, C. R.; Hartman, R. C.; Webb, J. R.
We observed the BL Lac object OJ 287 with the CGRO/EGRET instrument as a target of opportunity triggered by an outburst in its visual intensity. OJ 287 is well known as a high-amplitude variable in the optical and radio domain, and recurrent outburst behavior at nominal 11.6-year intervals have led to speculation that there may be some determinist…
ISOCAM imaging of AG CAR and HR Car.
Waters, L. B. F. M.; Trams, N. R.; Voors, R. H. M.
We present infrared images obtained with the ISOCAM instrument on board the Infrared Space Observatory of two Luminous Blue Variables (AG Car and HR Car). The images were obtained at eight wavelengths between 8.5 and 16µm using the Circular Variable Filters (CVFs), with a pixel size of 6 by 6arcsec and a total field of view of 192 by 192arcs…
Interstellar atom and pick-up ion fluxes along the ULYSSES flight-path.
Fichtner, H.; Mall, U.; Rucinski, D.
Neutral atom and pick-up ion flux computations using a hot model for hydrogen, helium, oxygen and neon along the trajectory of the Ulysses spacecraft, including predictions for the Extended Mission are reported and discussed. The feasibility of using absolute pick-up ion fluxes and pick-up ion flux ratios to derive the orientation of the heliosphe…
Interpretation of HMC Images by a Combined Thermal and Gasdynamic Model
Kührt, E.; Keller, H. U.; Knollenberg, J.
Images of comet Halley's nucleus taken by the HMC camera during the GIOT-TO encounter in 1986 show that a major part of the total dust production is localized in a few active areas which are the sources of gas-dust jets. The global dust distribution in the inner coma is dominated by two main jets roughly directed to the sun. A combination of a 1D …
Modulation of Anomalous Cosmic-Ray Ions by the Interplanetary Medium
Simnett, G. M.; Tappin, S. J.
The nature of comet Shoemaker-Levy 9 subnuclei from analysis of preimpact Hubble Space Telescope images
Mumma, Michael J.; Hahn, Joseph M.; Rettig, Terrence W. +2 more
We obtained Hubble Space Telescope (HST) Wide Field Planetary Camera images of comet Shoemaker-Levy 9 (S-L 9) prior to impact with Jupiter in 1994 to observe the effects of the Jovian gravitational field on the approaching fragments. The HST images were used to monitor the absolute brightness in the central regions of the comae, changes in the sur…
Far-UV Spectral Variability in the Gravitational Lens Candidate UM 425
Michalitsianos, A. G.; Maran, S. P.; Oliversen, R. J.
A comparison of recently acquired far-UV spectra with data obtained nearly 10 months earlier indicates changes have occurred in both absorption and ionization levels associated with Broad Absorption Line (BAL) structure in the QSO UM 425, a candidate gravitationally lensed system. These observations are compared with the initial discovery of O VI …
Detection of langmuir solitons: implications for type III burst emission mechanisms at 2ω PE
Goldstein, M. L.; Stone, R. G.; Thejappa, G.
We present the experimental verification of existing theoretical models of emission mechanisms of solar type III bursts at the second harmonic of the plasma frequency, ωpe. This study is based on the detection of Langmuir and envelope solitons by the Ulysses spacecraft inside three type III burst source regions. We show that the oscilla…