Engineering Papers⌕ Search

Engineering topics

Geballe, T. R.

Publications and source records attributed to Geballe, T. R..

88 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

The eight micron band of silicon monoxide in the expanding cloud around VY Canis Majoris

Observations of vibration-rotation transitions of silicon monoxide in VY CMa show that the lines originate in accelerating, expanding, and cool (600 K) layers of a circumstellar cloud at a distance of roughly 0.15 minutes from the central star. The central stellar velocity, as estimated from observed SiO P Cygni line profiles, is somewhat redshifted from the midpoint of the maser emission features. Most of the silicon is probably in the form of dust grains. The isotopic ratios of silicon are nearly terrestrial.

Geballe, T. R.↗
NASA NTRS1977

Ne II 12.8 micron emission from the galactic center. II

Recent observations of the 12.8-micron Ne II emission from the galactic center have revealed a region of primarily blueshifted emission in addition to the previously detected redshifted emission. It appears most likely that the blueshifted and redshifted emission come from separate clouds and that the dynamics of the ionized gas is dominated by the gravitational potential of the massive core at the galactic center. On the basis of the velocities and velocity dispersions, the total mass within a radius of 1 pc about the galactic center is estimated to be of the order of 4 million solar masses.

Wollman, E. R.↗
NASA NTRS1977

Detection of forbidden S III fine-structure emission in ionized nebulae

The 3P2-3P1 fine-structure line of doubly ionized sulfur has been detected at 534.41 + or - 0.03 kaysers in the spectra of NGC 7027, BD +30 deg 3639, and G333.6-0.2. The abundance of S(2+) and the electron density are discussed. The ionization of G333.6-0.2 is lower than expected from its luminosity.

Greenberg, L. T.↗
NASA NTRS1976

Spectral and spatial resolution of the 12.8 micron Ne II emission from the galactic center

High-resolution spectra of the Ne II 12.8-micron fine-structure line in emission from the galactic-center cloud Sgr A West show a line-center LSR radial velocity of +75 (+ or - 20) km/s and a velocity dispersion of about 200 km/s. The line has been observed with spectral resolution as high as 0.10 micron/cm and spatial resolution as high as 8 arcsec. This appears to provide a direct measurement of conditions in the 45-arcsec ionized region at the galactic center. The radial velocity and dispersion are more or less independent of position and indicate that events as recent as the last 10,000 years have given the ionized gas a systematic motion with respect to the massive stellar component of material at the galactic center. An upper limit of the order of 4 million solar masses for the mass within 0.8 pc of the galactic center is obtained from the velocity dispersion.

Wollman, E. R.↗
NASA NTRS1975

Observations and analysis of the Jovian spectrum in the 10-micron nu-2 band of NH3

Observations of the nu-2 band of NH3 in the Jovian atmosphere have been made at resolutions varying from 4 per cm to 0.15 per cm. The observations have been interpreted by computation of synthetic atmospheric spectra. Derived atmospheric parameters include a pressure of 0.5 atm at 145 K and a minimum temperature of 118 K.

Lacy, J. H.↗
NASA NTRS1975

Spectral and spatial resolution of the 12.8 micron Ne 2 emission from the galactic center

High-resolution spectra of the Ne II 12.8 micron fine-structure line in emission from the galactic center cloud Sgr A West show a line-center LSR radial velocity of + 75 + or - 20 km/sec. and a velocity dispersion of about 200 km/sec. The line has been observed with spectral resolution as high as 0.10/cm and spatial resolution as high as 8 sec. This appears to provide a direct measurement of conditions in the 45 sec. ionized region at the galactic center. The radial velocity and dispersion are more-or-less independent of position and indicate that events as recent as the last 4 million years have given the ionized gas a systematic motion with respect to the massive stellar component of material at the galactic center. An upper limit for the mass approximately equal to four million times the solar mass was obtained from the velocity distribution, with the mass located within 0.8 parsecs of the galactic center.

Wollman, E. R.↗
NASA NTRS1974

An upper limit on the evolution of carbon monoxide from Comet Kohoutek

An upper limit on the rate of evolution of CO from Comet Kohoutek has been obtained from a search for resonant scattering of sunlight near 4.7 microns. The observations were made approximately two months after perihelion. The rate of evolution of CO at that time was apparently less than that of CH3CN observed before perihelion.

Wollman, E. R.↗
NASA NTRS1974

Infrared pumping processes for SiO masers

The J = 2 to 1 transition of the first excited vibrational state (v = 1) Si(28)O(16) has recently been shown to produce maser amplification near 86,245 MHz in Orion A and in several stars. Two possible pumping mechanisms are proposed for such masers. One involves the near coincidence between the frequencies of the 1-0 (RO) and 3-2 (R18) transitions in Si(28)O(16). The other requires emission by SiO and reabsorption without the necessity for an accidental frequency coincidence. Each of these types of mechanisms may occur for other transitions of molecules in a medium illuminated by intense infrared radiation, or with strong temperature gradients.

Geballe, T. R.↗
NASA NTRS1974

Detection of O-17 in IRC+10216

Lines of the fundamental vibration-rotation band of C-12 O-17 have been observed near 4.7 micron in IRC+10216. Lines of C-12 O-18 were not detected, indicating a lower limit of 5 for the abundance ratio O-17/O-18. A lower limit of 200 and a probable value of 400 is obtained for the ratio O-16/O-17. The presence of C-12 O-17 is also indicated in alpha Her and alpha Sco.

Rank, D. M.↗