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Matthews, K.

Publications and source records attributed to Matthews, K..

At least 73 records · Page 4
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NASA NTRS1983

Observations of the line profile of Paschen alpha in 3C 273

Within the uncertainties, the P-alpha line profile is the same as those of H-beta, L-alpha, and C IV. It is therefore contended that if current models of broad-line-emitting clouds in quasars are correct, then the similarity of the P-alpha line profile to the L-alpha profile argues against a velocity field dominated by radial inflow or outflow. It is noted, however, that if the cloud motions are predominantly due to radial inflow or outflow, then the clouds must radiate more isotropically in L-alpha then current models predict. The observed similarity of the line profiles of P-alpha at 1.875 microns and of C IV at 1550 A leads to the conclusion that there is no differential reddening caused by dust between clouds moving at different velocities within the broad line region of 3C 273.

Sellgren, K.↗
NASA NTRS1983

Operation of integrating indium antimonide linear arrays at 65 K and below

The combination of a FET switch non-CCD readout architecture with high-quality mesa-photovoltaic indium-antimonide detector material has led to high-performance integrating linear imagers in the 1- to 5-micron region. These devices operate in the temperature regime below 100 K and provide very good dark current and responsivity uniformity (+ or - 2 percent). Test data will show performance at 65 K for a 512-element array and 46 K for a 128-element array. Useful integration times of 3600 seconds at 46 K and greater than 12 seconds at 65 K have been achieved. For both devices, kTC read noise levels of less than 1200 electrons have been measured.

Bailey, G. C.↗
NASA NTRS1982

Visual and infrared observations of the distant Comets P/Stephan-Oterma /1980g/, Panther /1980u/, and Bowell /1980b/

The paper reports combined visual imagery and spectroscopy, near-infrared spectroscopy, and broadband infrared photometry of comets P/Stephan-Oterma (1980g), Bowell (1980b), and Panther (1980u) at intermediate heliocentric distances. The visual data indicate the existence of solid grains in extended halos around the nuclei of the three comets. Broadband near-infrared and thermal infrared measurements of Comet Panther suggest the presence of 2-4-micron-radius particles in the coma which most likely contain molecules incorporating the N-H bond, but which are more complex and less volatile than NH3. Such molecules can be produced in the grains by cosmic-ray reprocessing. Near infrared spectral features identical to those seen in comet Panther similary suggest the presence of a molecule incorporating the N-H bond in comet Bowell.

Jewitt, D. C.↗
NASA NTRS1982

Maps of the rings of Uranus at a wavelength of 2.2 microns

Maps of the ring system of Uranus, as seen in reflected sunlight at a wavelength of 2.2 microns, are presented for May 1978 and July 1979. Large azimuthal brightness variations revealed by these maps are consistent with the variable width established for the epsilon ring from occultation studies and support the existing elliptical model for this ring. An upper limit of approximately 0.010 is placed on the normal optical depth of any broad (approximately 5000 km wide) axisymmetric ring component. There exists, however, an unexplained east-west asymmetry in the May 1978 map. In addition, multiaperture broadband infrared photometry of Uranus is reported, from which the geometric albedo of the planet at wavelengths of 1.25, 1.65, and 2.2 microns and the geometric albedo of the rings at 2.2 microns are derived.

Matthews, K.↗
NASA NTRS1982

The upper atmosphere of Uranus - A critical test of isotropic turbulence models

Observations of the August 15, 1980, Uranus occultation of KM 12, obtained from Cerro Tololo InterAmerican Observatory, European Southern Observatory, and Cerro Las Campanas Observatory, are used to compare the atmospheric structure at points separated by approximately 140 km along the planetary limb. The results reveal striking, but by no means perfect correlation of the light curves, ruling out isotropic turbulence as the cause of the light curve spikes. The atmosphere is strongly layered, and any acceptable turbulence model must accommodate the axial ratios of greater than about 60 which are observed. The mean temperature of the atmosphere is 150 plus or minus 15 K for the region near number density 10 to the 14th per cu cm. Derived temperature variations of vertical scale approximately 130 km and amplitude plus or minus 5 K are in agreement for all stations, and correlated spikes correspond to low-amplitude temperature variations with a vertical scale of several kilometers.

French, R. G.↗
NASA NTRS1982

Infrared standard stars

The results of an observational program aimed at setting up a network of faint near-infrared standards of sufficient accuracy are reported. The network covers both northern and southern hemispheres and includes standards red enough to provide at least a limited check on color transformations. The standards are set up at J (1.2 micron), H (1.6 micron), K (2.2 microns), and L (3.5 microns), and their H2O and CO molecular absorption indices are determined. The problem of color transformations between observatories is discussed briefly. All magnitudes presented are transformed to the natural system defined by the CIT observations.

Elias, J. H.↗
NASA NTRS1982

Infrared, optical, and ultraviolet observations of hydrogen line emission from Seyfert galaxies

Nearly simultaneous observations are reported of P-alpha, H-alpha, and H-beta emission from 18 Seyfert galaxies and of Ly-alpha from eight of these galaxies. In many cases, P-alpha is stronger relative to the Balmer lines than is predicted by recombination calculations; reddening appears to be required. Dispersion in the P-alpha/H-alpha/H-beta ratios orthogonal to the reddening track indicates that high densities or optical depths also affect the line flux ratios. Several galaxies, notably NGC 1275, have very low P-alpha/H-alpha ratios. High densities, large optical depths, and reddening probably all contribute to the low observed Ly-alpha/H-beta ratios.

Lacy, J. H.↗
NASA NTRS1982

Infrared/optical energy distributions of high redshifted quasars

Measurements at 1.2, 1.6 and 2.2 microns were combined with visual spectrophotometry of 21 quasars having redshifts z or = 2.66. The primary result is that the rest frame visual/ultraviolet continua of the high redshift quasars are well described by a sum of a power law continuum with slope of approximately -0.4 and a 3000 A bump. The rest frame visual/ultraviolet continua of these quasars are quite similar to that of 3C273, the archetype of low redshift quasars. There does not appear to be any visual/ultraviolet properties distinguishing high redshift quasars selected via visual or radio techniques.

Soifer, B. T.↗
NASA NTRS1982

Radial widths, optical depths, and eccentricities of the Uranian rings

Observations of the stellar occultation by the Uranian rings of 15/16 August 1980 are used to estimate radial widths and normal optical depths for segments of rings 6, 5, 4, alpha, beta, eta, gamma, and delta. Synthetic occultation profiles are generated to match the observed light curves. A review of published data confirms the existence of width-radius relations for rings alpha and beta, and indicates that the optical depths of these two rings vary inversely with their radial widths. Masses are obtained for rings alpha and beta, on the assumption that differential precession is prevented by their self-gravity. A quantitative comparison of seven epsilon-ring occultation profiles obtained over a period of 3.4 yr reveals a consistent structure, which may reflect the presence of unresolved gaps and subrings.

Nicholson, P. D.↗
NASA NTRS1982

Observations of NGC 604 over six decades in frequency

Maps in the near-infrared, H-alpha and radio continuum have been obtained of NGC 604, the brightest H II region complex in M33, as well as a measurement of the UV spectrum of the ionizing star cluster. The data show that NGC 604 consists of about ten components of typical size 10 pc, embedded in a much larger envelope with dimensions of 225 pc. At least one component is optically almost completely obscured; it is located close to another object that is only detected in the near-infrared and whose nature is uncertain.

Israel, F. P.↗
NASA NTRS1982

Infrared properties of serendipitous X-ray quasars

Near infrared measurements were obtained of 30 quasars originally found serendipitously as X-ray sources in fields of other objects. The observations show that the infrared characteristics of these quasars do not differ significantly from those of quasars selected by other criteria. Because this X-ray selected sample is subject to different selection biases than previous radio and optical surveys, this conclusion is useful in validating previous inferences regarding the infrared colors of 'typical' quasars.

Neugebauer, G.↗
NASA NTRS1982

Infrared observations of the Uranian rings

Maps of the Uranian rings at 2.2 microns and spectrophotometric observations covering 2.0 to 2.4 and 2.9 to 3.9 microns are discussed. The maps reveal a 2:1 azimuthal brightness variation whose amplitude and phase are consistent with the width variation and apsidal precession of the epsilon ring. Comparison with models based on stellar occultation data leads to an upper limit of 0.01 on the normal optical depth of any broad (5000 km wide), diffuse component of the ring system. A significant east-west asymmetry, corresponding to a brightening of the near side of the rings relative to the far side, is unexplained. The spectrum of the rings is flat over the range 2.1 to 3.9 microns. There is no spectroscopic evidence for the presence of H2O.

Nicholson, P. D.↗
NASA NTRS1981

Extremely red compact radio sources - The empty field objects

Radiation of 10 microns has been detected from 1413+135, one of the very red objects discovered by Rieke, Lebofsky, and Kinman (1979) at near-infrared wavelengths. The spectrum of this object flattens at wavelengths longer than 2.2 microns. Upper limits are also given for the 10-micron emission from 2255+14, 0026+34, and 0406+121. Photometry between 1.25 and 2.2 microns confirms the variability of 1413+135, 2255+41, and 0406+121. Five percent resolution spectra of 1413+135 and 0406+121 between 1.5 and 2.4 microns show no emission or absorption lines. The spectral data rule out the possibility that 1413+135 is a quasar with normal line strengths and a redshift less than 1.3 and greater than 4. The lack of features of the 1.5-2.4-micron spectra, the rapid variability, and the overall shape of the radio, infrared, and X-ray energy distributions are consistent with a BL Lac nature for these objects.

Beichman, C. A.↗
NASA NTRS1981

The diameter and albedo of 1943 Anteros

The results of broadband visual and infrared photometry of the Apollo-Amor asteroid 1943 Anteros during its 1980 apparition are reported. By means of a radiometric model, a diameter of 2.3 + or - 0.2 km and a visual geometric albedo of 0.13 + or - 0.03 is calculated. The albedo and reflectance spectrum of Anteros imply that it is a type S asteroid. Thus, Anteros may have a silicate surface similar to other Apollo-Amor asteroids as well as some stony-iron meteorites.

Veeder, G. J.↗