Search Publications
Signal-to-Noise Ratios in IUE Low-Dispersion Spectra. II. Photometrically-Corrected Images
Ayres, Thomas R.
The character of detector noise is explored in photometrically-corrected images from the shortwavelength and longwavelength prime intensified vidicon cameras of the International Ultraviolet Explorer. A protocol is proposed for deriving realistic "noise models"--crucial to the application of Optimal extraction algorithms like that of Kinney, Bohli…
Optical and ultraviolet observations of the star LkHα 264.
Collier Cameron, A.; Gameiro, J. F.; Lagor, M. T. V. +1 more
We present new ultraviolet and optical data for the classical T Tauri star LkH-alpha 264. The most important features in the UV spectrum are identified and their fluxes are measured. These fluxes are then compared to the corresponding values in the sun and in other T Tauri stars. Our time series of high-resolution spectra for the regions of the H-…
Relativistic electron flux anisotropies in the duskside Jovian magnetosphere: a test for source location and escape mechanism
Simpson, J. A.; McKibben, R. B.; Zhang, Ming
Results of anisotropy analyses of >∼ 3 MeV electron flux data obtained by the high-energy telescope of the COSPIN experiment on Ulysses are presented for the period from day 40 to day 45 of 1992, when the spacecraft was outbound from Jupiter in the duskside high-latitude magnetosphere and magnetosheath. At small L-shells or minimum magnetic lat…
The radio and optical structure of 3C 66B.
Sparks, W. B.; Macchetto, F.; Miley, G. K. +1 more
We report new, high-resolution radio observations of the jet in 3C 66B. The filaments in the optical jet seen in the HST image of Macchetto et al. are also visible in the radio image. The structure of the radio jet is complex and filamentary beyond the brightest knot. It is consistent with the HST image, which appears to consist of a central kinke…
The Distant Future of Solar Activity: A Case Study of beta Hydri. III. Transition Region, Corona, and Stellar Wind
Linsky, J. L.; Simon, T.; Ayres, T. R. +4 more
The paper investigates the secular decay of solar-type activity through a detailed comparison of the present sun with the very old solar-type star, Beta Hyi, taken as a proxy of the future sun. Analyses of successive atmospheric layers are presented, with emphasis of the outermost parts. The FUV emission lines for the transition zone are among the…
Observations of electron plasma waves upstream of the Jovian bow shock
Kellogg, P. J.; MacDowall, R. J.; Canu, P. +3 more
The Ulysses spacecraft encountered the planet Jupiter in February 1992, on its journey towards high heliospheric latitude. During the approach to the planet, as well as on the outbound pass, while receding from the Jovian bow shock, the Plasma Frequency Receiver that is part of the Unified Radio and Plasma Wave experiment (URAP) recorded bursts of…
Quantitative Spectroscopy of K 648 --the PNN of Ps1 in the Globular Cluster M15
Dreizler, Stefan; Werner, Klaus; Heber, Ulrich
We report preliminary results of a quantitative study of high resolution UV and optical spectra of K648 obtained with the Hubble Space Telescope and the Calar Alto 3.5 m telescope, respectively. Using state of the art NLTE model- atmospheres we determine atmospheric parameters and the abundances of hydrogen, helium and carbon. K648 is found to be …
Damped Lyman-Alpha Absorption in Q0957+561A, B
Turnshek, David A.; Bohlin, Ralph C.
A series of archival IUE low-dispersion spectral observations of the double quasar Q0957 + 561A, B are analyzed. The components of this gravitationally lensed quasar are separated by ~6". Damped Lyα absorption at redshift z_abs_ = 1.3911 with neutral hydrogen column density N(H I) ~ 7 x 10^19^ cm^-2^ is present in the spectra of both the A and B c…
High-velocity spectra features in V854 Centauri : evidence for dust formation ?
Lawson, W. A.; Whitney, B. A.; Clayton, G. C. +1 more
Low-dispersion lUE spectra of V854 Cen show apparent shifts or splitting in the λ2325 C II], λ2800 Mg II, λ2851 Mg I and λ2965 C I lines which, if kinematic, indicate velocities in excess of 1000 km s-1. The variations are seen in all the UV emission lines simultaneously. The line splitting seems to occur at times near phase 0.0 (maximu…
Evidence for Precession of the R Aquarii Jet
Hollis, J. M.; Michalitsianos, A. G.
Several models of the R Aqr northeast jet have been proposed which attempt to explain the presence of shock excitation, resulting in a confusing picture of this nearest astrophysical jet. This paper compares observations of the jet in the R Aqr system with the HST's Faint Object Camera (FOC) and radio continuum images acquired with the VLA. The fo…