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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 145 records · Page 8
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NASA NTRS1976

Optical pulsations in HZ Herculis. 5. Pulse-resolved spectrophotometry

Digital spectra of HZ Herculis were obtained with 10 A resolution in the 3,600 - 6,000 A region, synchronously dividing the 1.24-s optical pulsation period into eight 155-ms phase bins. The optical pulses are detected in the data, but their fractional amplitude is only 0.08 percent, a factor of 4 less than typically observed. The separate spectra of each one-eighth of the pulse are identical to within the statistics of the observation. If the X-ray to optical pulse reprocessing mechanism concentrates the optical pulsations into discrete spectral line features, data require the pulses to be distributed among more than four such lines.

Margon, B.↗
NASA NTRS1976

Spectrophotometry of the unusual optical candidate for 3U 1728-24 (=GX 2+5 = GX 1+4) a recurrent nova?

The spectrum of the object suggested as a possible optical counterpart of GX 2+5, was studied, using the image tube scanner attached to the 3-m telescope of Lick Observatory. An improved X-ray error box obtained with Copernicus strongly supports this proposed identification. The candidate displays all the characteristics of the symbiotic stars and the related recurrent novae. The spectrum reveals the presence of an M star together with a blue component and a large number of emission lines displaying a wide range of ionization. There is evidence of variability of both the continuum and the line intensities. This object provides strong support for the often proposed association of some X-ray sources with nova-like systems.

Davidsen, A. F.↗
NASA NTRS1975

Spectrophotometry of Comet Kohoutek /1973f = 1973XII/

Spectrum scans have been obtained of Comet Kohoutek with a Fourier spectrometer at heliocentric distances from 0.55 to 1.05 AU. The useful spectral range is roughly 3800-8400 A and the resolution is about 10-15 A at 5000 A. Large variations occurred in the gas-to-dust ratio (pre- versus postperihelion) and in the relative strength of the NH2 bands (with heliocentric distance). There is a smaller change in the ratio of CN to C2 emission. The Swan bands of C2 show the customary anomaly in strengths implying highly non-Boltzmann distributions among vibrational levels. The red and violet CN system fluxes are in slightly better agreement with laboratory data on oscillator strengths than results on previous comets. Other species measured include Na, (O I), CH, and C3.

Ahearn, M. F.↗
NASA NTRS1975

Ultraviolet photometry and spectrophotometry of Algol

OAO-2 blue and UV light curves and spectrophotometric observations are used to establish effective temperatures and luminosities for the three components of the eclipsing Algol (beta Persei) system. An essentially complete energy distribution is given for Algol, and the fundamental properties - geometrical quantities, wavelength-dependent quantities and derived astrophysical quantities - are presented for the star.

Eaton, J. A.↗
NASA NTRS1976

Optical and infrared spectrophotometry of 18 Markarian galaxies

Slit spectra, spectrophotometric scans, and infrared broad-band observations are presented for 18 Markarian galaxies with emission lines. Eight of the program galaxies can be classified as Seyfert galaxies. Arguments are given that thermal, nonthermal, and stellar radiation components are present. Broadly speaking, one group of Seyfert galaxies is characterized both by the presence of a high-density region of gas and by a continuum dominated by nonthermal radiation. The continua of the remaining program Seyferts, which do not have a high-density region of gas, are dominated by thermal radiation from dust and a stellar continuum. The 10 galaxies which are not Seyfert galaxies are shown to be examples of extragalactic H II regions; there is evidence for thermal emission from dust being present at 10 microns in four of these galaxies.

Neugebauer, G.↗
NASA NTRS1976

Spectrophotometry and UBVRI photometry of Eros

Spectrophotometric and broad-band photoelectric observations of Eros are reported. No existing meteorite spectrum matches the asteroid data directly. Assemblages of iron or stony-iron with ordinary-chondrite material generate the best match for the reflectivity curve of Eros. Variability was found in the 0.6 micron band and V-R and V-I colors.

Wisniewski, W. Z.↗
NASA NTRS1976

Spectrophotometry /0.33 to 1.07 microns/ of 433 Eros and compositional implications

The spectral reflectance (0.33-1.07 micrometers) for the asteroid 433 Eros was determined as a function of rotational phase during January 28-30, and February 15, 1975. Interpretation of absorption features suggests Eros is composed of an undifferentiated assemblage of moderate to high temperature minerals (iron, pyroxene, and olivine, but no carbon). H-type ordinary chondrites are such assemblages, but it would be premature to conclude that Eros is like an H chondrite meteorite in composition until a better understanding is reached of possible physical differences between laboratory powders and asteroid regoliths for metal-bearing assemblages. There are no large-scale major compositional variations on the different sides of Eros.

Pieters, C.↗
NASA NTRS1976

8 to 13 micron spectrophotometry of compact sources in NGC 7538

Three infrared and radio sources in NGC 7538 have been observed with 1% spectral and 5-arcsec spatial resolution. The very small southern source shows a deep silicate absorption feature at 9.7 microns, while the northern extended source shows little or no silicate absorption, but has a 12.8-micron emission line from Ne II. The data imply that the compact source has a gas-to-dust ratio of 75 inside the ionized region. The extended source only 10 arcsec away has a gas-to-dust ratio implied by the 10-micron data alone of 30,000, but the true ratio must be much lower to account for published 20-micron measurements.

Willner, S. P.↗
NASA NTRS1976

Spectrophotometry of Jupiter

Spectrophotometric maps of Jupiter were made between 24 and 27 (UT) November 1974 on the McMath Solar Telescope at Kitt Peak National Observatory. We report a comparison between observed scaled reflectivities of the Jovian North Tropical Zone and the North Equatorial Belt at System II longitudes between 195 and 205 degrees. The belt/zone reflectivity ratios between 430 and 740 nm are related to the optical transmission curves of the organic and/or sulfur polymers synthesized by Khare and Sagan in a simulated Jovian atmosphere.

Wamsteker, W.↗
NASA NTRS1976

Instrumentation for solar spectrophotometry at extreme ultraviolet and soft X-ray wavelengths

The solar extreme ultraviolet and soft X-ray (XUV) spectrum at wavelengths between 20 and 300 A contains a wealth of emission lines from ions formed at temperatures from 10 to the 5th K to greater than 2 x 10 to the 7th K. The requirements for high resolution spectrophotometric instrumentation are discussed in the light of data obtained with extreme ultraviolet and X-ray telescopes flown on Skylab. The design of a grazing-incidence spectroheliometer for active region and flare studies over the wavelength range from 40 to 630 A is presented and recently developed high-efficiency detectors and detector-arrays for use at XUV wavelengths are described.

Timothy, J. G.↗
NASA NTRS1976

Spectrophotometry of the X-ray binary HZ Herculis

An extensive set of absolute spectrophotometric observations of HZ Her over the wavelength range from 3300 to 10,000 A is presented and analyzed to determine to what extent the observations can be interpreted in terms of a model for the system. The specific model to be tested consists of a large star (HZ Her) with a hot cap beneath the X-ray source, an accretion disk around the X-ray source, and a gas stream flowing between the primary star and the disk. It is found that the model is compatible to a large extent with the detailed observations and that the physical characteristics of the various components can be derived. The mass, luminosity, and radius of the primary star, the mass of the X-ray object, and the orbital dimensions are obtained by analyzing the energy distribution at minimum light and X-ray eclipse data. The angle and effective temperature of the hot cap on the primary are also determined along with the energy distribution, diameter, and thickness of the accretion disk. It is concluded that HZ Her fills its Roche lobe and is an A7 V star, that the logarithm of its surface gravity is about 3.6, and that the mass of the X-ray object is 1.95 solar masses.

Oke, J. B.↗
NASA NTRS1977

Spectrophotometry of the transient X-ray source A0620-00

Optical observations of the transient X-ray source A0620-00 over the wavelength range from about 3200 to 6600 A are analyzed which were made with the 5-m Hale telescope using a multichannel spectrometer, a digital spectrograph with a cooled integrating SIT vidicon, and an image photon-counting system attached to the camera of the coude spectrograph. Infrared observations at 1.65, 2.2, and 3.5 microns are also examined. Individual spectral lines of special interest are discussed, the E(B-V) color excess is estimated to be about 0.40, and a distance of 1200 pc is adopted. Analysis of the continuous spectrum yields several simple binary models. A specific model is proposed in which one of the continuum sources is an optically thick object characterized by a model atmosphere at a temperature of 25,000 to 30,000 K and the second source is either a cool black body at 4000 K or a partially optically thick source of bound-free plus free-free radiation from a hydrogen gas with an electron temperature of at least 100,000 K. Some possible parameters of these sources and of the accretion disk are considered.

Oke, J. B.↗
NASA NTRS1977

8 to 13 micrometer spectrophotometry of compact sources in W3

Three infrared and radio sources in W3 (continuum) and one in W3(OH) have been observed with 1% spectral resolution. Three sources show deep silicate absorption features; the remaining source shows little silicate absorption and has three emission lines. One source, IRS 5, has the deepest silicate absorption known and can be used to determine the wavelength dependence of silicate extinction. Such properties of the sources as dust masses and luminosities are discussed.

Willner, S. P.↗
NASA NTRS1977

Satellite spectrophotometry and surface compositions

A summary of available spectrophotometric data for planetary satellites is presented. Most data given is for the 0.3 to about 3 micron spectral region. The spectrophotometric results are compared with spectral reflectivity curves of cosmologically abundant substances to provide information on the possible composition of surfaces of planetary satellites, excluding earth's moon. Water ice and other frosts appear to be common in the outer solar system; however, most surface compositions cannot be unambiguously defined.

Johnson, T. V.↗
NASA NTRS1977

Further spectrophotometry of the transient X-ray source A0620-00

Observations of the transient X-ray source A0620-00 in November 1976 show that the optical object had an apparent visual magnitude of 18.35. The spectrum is cool and shows that one component of the light comes from a K5 V to K7 V star. The distance is estimated to be 870 pc if the cool star is normal. Some support for the 7.8-day X-ray period recently found is provided by observations made in 1975 during the outburst. In addition to the cool K star, there is a second radiation source which has a flat spectrum. This source can be modeled by a 10,000-K blackbody with a radius (if spherical) of 17,000 km plus a 4000-K blackbody with a radius of 13,400 km and is probably a residual accretion disk. It is very unlikely that the K star can fill its Roche lobe, so that mass transfer to a neutron-star companion by this mechanism is unlikely. It is possible that the K star is losing mass by processes such as those that occur in T Tauri stars.

Oke, J. B.↗
NASA NTRS1978

Spectrophotometry of OH 26.5+0.6 from 2 to 40 microns

Airborne and ground-based observations show that OH 26.5+0.6 has strong 10 micrometers and weak 18 micrometers silicate absorptions superposed on an overall energy distribution much like a blackbody. The flux level, color temperature, and depth of the 10 micrometers absorption have varied during two years of observations. A model of the source as a late-type variable star that has ejected an optically thick dust shell is suggested; the mass-loss rate implied is greater than about 0.00001 solar masses per year. The fact that significant flux from the source is observed between 4 and 7 micrometers is evidence that oxygen-rich dust has significant opacity in that wavelength range.

Forrest, W. J.↗
NASA NTRS1978

Airborne infrared spectrophotometry of Mira variables

Airborne spectrophotometric observations of R Cas near minimum and maximum light, R Leo near minimum, and NML Tau near maximum are reported which were obtained over the wavelength range from 1.2 to 4 microns with 1.5% resolution. The spectral energy distributions of the three stars at the indicated times are presented, and it is shown that the H2O bands at 1.4, 1.9, and 2.7 microns are clearly evident in all the spectra, while the absorption bands of CO at about 1.6 and 2.3 microns are probably present although they are masked by the strong water vapor features. The results indicate that water vapor is the dominant opacity source in the atmospheres of Mira variables, that R Leo and NML Tau may be fitted well over the entire spectrum by respective single temperatures of 2250 and 1800 K, and that R Cas near both minimum and maximum cannot be adequately described by one temperature over the entire wavelength range investigated. The shapes and depths of the absorption bands are determined together with the apparent angular diameter of each star and the equivalent widths of the H2O + CO absorption bands. It is concluded that water vapor absorption is more strongly correlated with color temperature than with spectral type for R Cas and R Leo.

Strecker, D. W.↗