Engineering topics

Judge, P.

Publications and source records attributed to Judge, P..

4 records

NASA NTRS1990

On the disappearance of O I in some high-luminosity cool stars

Far UV spectra and flux measurements of cool giant and supergiant stars, focusing on the O I (UV 2) and S I/Si II fluxes and their dependence on stellar parameters are presented. The de-reddened O I surface fluxes vary by factors of several hundred over the 11 stars in the sample and, at a given luminosity, decrease with decreasing effective temperature. No flux at all is detected in the three M supergiants observed to date. In contrast, the S I/Si II blend near 1810 angstrom is clearly detected in all the stars. Its strength generally increases with luminosity, but has little effective temperature dependence. Possible explanations for the behavior of O I include changes in the intensities of Lyman alpha and beta which excite the lines of S I and O I, respectively, as well as scattering and/or absorption of the O I flux in a dense, circumstellar gas shell.

Carpenter, K. G.↗

NASA NTRS1990

Mass loss upper limits for A and F dwarfs

The upper limits of the ionized mass losses of A- and F-type main sequence stars are obtained with the VLA to investigate the theory that pulsationally driven winds contribute to substantial mass loss in the stars. The upper limits are found to be at least one order of magnitude lower than the mass-loss loci proposed by Willson et al. (1987). Because any wind flowing from the stars should be detectable, the notion that A dwarfs are evolving into G dwarfs cannot be supported by the amount of mass that A and F dwarfs are shown to be losing.

Brown, A.↗

NASA NTRS1988

Direct UV observations of the circumstellar envelope of alpha Orionis

Observations were made in the IUE LWP camera, low dispersion mode, with alpha Ori being offset various distances from the center of the Long Wavelength Large Aperture along its major axis. Signal was acquired at all offset positions and is comprised of unequal components of background/dark counts, telescope-scattered light, and scattered light emanating from the extended circumstellar shell. The star is known from optical and infrared observations to possess an extended, arc-minute sized, shell of cool material. Attempts to observe this shell with the IUE are described, although the deconvolution of the stellar signal from the telescope scattered light requires further calibration effort.

Stencel, R. E.↗

NASA NTRS1986

High-dispersion observations of alpha Bootis (K1 III) with the International Ultraviolet Explorer

Echelle spectrograms were obtained of the early-K red giant Arcturus in the far UV 1150-2000 A and middle-UV 2000-3200 A regions. Faint emission from forbidden Si II at 1892.0 A was detected. A surface flux of C IV was measured that was less than 1 percent of the solar surface flux. An observed faint spectral structure near 1380 A is believed due to the bands of the A-X fourth positive system of CO fluoresced by strong chromospheric emissions of the O I triplet. Constraints on the chromospheric structure, as evidenced by the fluorescent emissions and density-sensitive line ratios from multiplet UV lines of forbidden C II, are discussed.

Ayres, T. R.↗