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Westphal, J. A.

Publications and source records attributed to Westphal, J. A..

At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Evidence for a supermassive object in the nucleus of the galaxy M87 from SIT and CCD area photometry

Results are presented for broadband three-color (BVR) photometric observations of the peculiar elliptical radio galaxy M87, which were obtained with digital two-dimensional SIT and CCD detector systems on the Palomar 60-in. and 200-in. telescopes. The observations and the reduction procedures for the digital data are outlined, the luminosity profile of M87 is given, and a nuclear luminosity spike is found to be centered within 0.02 arcsec of the center of M87. Attempts are made to fit various theoretical models to the luminosity profile, and a satisfactory fit is obtained between the observed profile and a model involving a massive black hole in the galactic nucleus. A model-independent dynamical analysis of the central regions is performed which indicates that the nucleus of M87 contains a supermassive object of about 5 billion solar masses with a radius of no more than 100 pc and an M/L ratio of at least 60. The possible nature of this object is considered, and it is concluded that M87 is probably the most plausible candidate for a massive black hole in a galactic nucleus.

Young, P. J.↗
NASA NTRS1977

Silicon vidicon imaging of Jupiter - 4100- to 8300-A absolute reflectivities and limb darkening of spatially resolved regions

Jupiter was observed in six continuum wavelength channels in the region 4100-8300 A, using a silicon vidicon imaging photometer. Spectral reflectivities and high spatial resolution limb-darkening curves for several belts and zones have been extracted from the data. Simple model fits to the data yield information regarding spectral and spatial variations in single-scattering albedos and shape of particle single-scattering phase functions. Belts appear to be more backscattering than zones, particularly in the blue. The data are in moderate agreement with limb-darkening predicted by models derived from the center-to-limb variation in equivalent width of the H2 4-0 S(1) quadrupole line (Cochran, 1976) in the South Tropical Zone, but strongly disagree with the results of such models for the North Equatorial Belt.

Diner, D. J.↗
NASA NTRS1977

Infrared imaging of Jupiter in the 8-14-micrometer spectral region

High-spatial-resolution images of Jupiter were produced on the Hale 200-in. telescope. A programmable wobbling secondary was used to raster-scan the planet with 64 by 64 1-arcsec pixels. Images were made with broadband (8-14 microns) and several 1- and 2-micron-wide filters. All images reveal a belt-and-ozone structure similar to visible photographs. Belts in the broadband data appear to be about 2 K hotter than zones, but contrast varies markedly in different parts of the 8-14-micron spectral region. The lowest belt-zone contrast is found in the hydrogen-opacity-dominated region at 12.5 microns, while images at 9.5 microns exhibit the greatest contrast. Isolated areas are observed to be as much as 4 K hotter than surrounding areas at 9.5 microns. This large contrast is probably due to variations in the distribution of the ammonia clouds in the upper atmosphere.

Terrile, R. J.↗
NASA NTRS1977

The vertical cloud structure of Jupiter from 5 micron measurements

From 5-micron high-spatial-resolution images of Jupiter, flux-frequency histograms of the equatorial region show a trimodal distribution of brightness temperatures. Combined with limb-darkening measurements, a three-layer cloud model for Jupiter is developed. The highest, coldest clouds, apparently homogeneous and displaying relatively little limb darkening, cover the zones. These clouds are not present over the belts, allowing observational access to deeper regions. The belts appear heterogeneous: small, localized hot areas show enhanced limb darkening, while much of the belt is distinctly cooler and exhibits shallower limb darkening. These belt properties can be explained by a cool emitting layer superposed upon a hot, dense cloud deck.

Terrile, R. J.↗
NASA NTRS1976

Infrared imaging of Venus - 8-14 micrometers

High-spatial-resolution images of Venus were obtained at wavelengths between 8 and 14 microns when the planet was at a phase angle of 112 deg with the morning terminator in view. The images confirm the existence of a previously mapped flux anomaly near the south pole and show evidence of other infrared features, presumably transient in nature. Flux differences of 2-7% were measured, corresponding to brightness temperature variations of roughly 1-3 K. The images also confirm the difference between polar and equatorial limb darkening. Finally, evidence is presented for a night-day asymmetry in the flux, with the brightness temperature greater by about 2 K on the sunlit side.

Diner, D. J.↗
NASA NTRS1974

Infrared sky noise survey

A 10 micron infrared sky noise survey, which was conducted during the period from June 1, 1970 to June 30, 1974, is reported along with associated electronics and recording equipment which was developed and deployed for periods up to 18 months at various potential or existing infrared observing sites in the U.S., Mexico, and Chile. The results of the data activity are given, and variables are defined which influence the intensity and duration of the sky noise.

Westphal, J. A.↗
NASA NTRS1974

Five-micron pictures of Jupiter

Several hundred five-micron 'video' pictures of Jupiter, with 1-sec resolution, made during September, October, and December 1973 and compared with color photographs, are shown to exhibit direct, detailed correlations with the darker 'purple' features. Forty-four of these pictures were made just before the Pioneer-10 encounter.

Westphal, J. A.↗
NASA NTRS1973

Observations of 7.9-micron limb brightening on Jupiter.

Gillett et al. (1969) observed that the brightness temperature in the strong 7.7-micron CH4 band was higher than at the neighboring wavelengths (where the absorption was expected to be less) in the Jovian spectrum from 2.8 to 13 microns. This observation was interpreted as being caused by a temperature inversion in the upper atmosphere of Jupiter. This interpretation is checked by measuring the variation of the brightness temperature from the center to the limb of the disk, and is confirmed by the observation of limb brightening, rather than the usual limb darkening, at a certain wavelength within the 7.7-micron CH4 band.

Gillett, F. C.↗
NASA NTRS1973

Application of the SIT vidicon to astronomical measurements.

Review of the results of a detailed investigation of the properties and merits of silicon target (SIT) vidicon photometry, compared to previous photoelectric and photographic photometry, in astronomy applications. Following a description of the SIT-vidicon based photometry system and of its operating procedures, the data reduction methods are examined, and some of the results obtained are discussed.

Westphal, J. A.↗
NASA NTRS1972

On the optical search for Centaurus X-3.

Elimination of the optical eclipsing binary LR Cen as a candidate for Cen X-3 on the basis of a real discrepancy of orbital periods. It is believed that the position coincidence of Wray 795 with Cen X-3 is not statistically significant.

Brucato, R. J.↗
NASA NTRS1972

Infrared Observations of Comets Ikeya-seki (1965f) and Bennett (1969i)

Measurements of Comet Bennett (1969i) from 1.2 microns to 10 microns indicate the presence of material at a temperature of 590 K on 6 April 1970. The excellence of the fit of the flux values to a 590 K blackbody severely restricts the possible range of materials present. Specifically it precludes simple isolated small particle models to explain the excess temperature observed.

Westphal, J. A.↗
NASA NTRS1972

Infrared sky noise study

The hardware and techniques to measure and compare sky noise at several sites were studied, and a device was developed that would maximize its output and minimize its output for modulation. The instrument and its functions are described. The nature of sky emissions and the fluctuation, gaseous sources of sky noise, and aerosol sources are discussed. It is concluded that sky noise really exists, and the spatial distribution of the sky noise sources are such that observed noise values are linear functions of chopping stroke.

Westphal, J. A.↗
NASA NTRS1972

Infrared diameter of IRC + 10216 determined from lunar occultations.

Lunar occultations of IRC + 10216 have been used to determine the size of the regions emitting 2.2-, 3.5-, 4.8-, and 10-micron radiation. The results are interpreted as the first direct measurement of the physical size of a dust shell surrounding a late-type star.

Toombs, R. I.↗
NASA NTRS1972

The clouds of Jupiter - Observational characteristics.

Most current models for the Jovian cloud system make use of an erroneous value for the temperature of the planet evaluated at 5 microns. Recent observations at this wavelength show that the emitted radiation is strongly localized and that it exhibits temporal variations. It is not clear that meaningful temperatures can be derived from such measurements and this plus other observations discussed herein suggest that various models proposed for the clouds require reexamination.

Owen, T.↗