Search NASA⌕ Search

SEARCH · Search NASA

Results for “Spectrophotometry”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 415 records · Page 23
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Minor planets and related objects. XVIII - UBV photometry and surface composition

New photometric observations on the UBV system are presented for 45 asteroids, bringing the total to 91 for which complete UBV colors are available. The reduced magnitudes B (1, 0) scatter about the adopted catalog values by + or - 0m, 25, with negligible systematic difference. The UBV colors fall into three distinct groups which correspond almost perfectly to the S (silicaceous or stony), C (carbonaceous), and U (unclassifiable) asteroid types recently identified from polarimetry, infrared radiometry, and narrow-band spectrophotometry. It becomes possible to classify asteroids from UBV observations alone. The S asteroids have colors very similar to those of L and LL ordinary chondrites, and some of the U objects are consistent in color with nickel-iron or enstatite-rich meteorites, but no meteorites appear to have the UBV colors of the C asteroids. The asteroid C and S compositional types have no exact counterparts among the surfaces of natural satellites.

Zellner, B.↗
NASA NTRS1975

High temperature plasma in beta Lyrae, observed from Copernicus

High-resolution UV spectrophotometry of the complex close binary system beta Lyrae was performed with a telescope spectrometer on board Copernicus. Observations were made at phases 0.0, 0.25, 0.5, and 0.75 with resolutions of 0.2 A (far-UV) and 0.4 A (mid-UV). The far-UV spectrum is completely dominated by emission lines indicating the existence of a high-temperature plasma in this binary. The spectrum of this object is unlike that of any other object observed from Copernicus. It is believed that this high-temperature plasma results from dynamic mass transfer taking place in the binary. The current results are compared with OAO-2 observations and other observational results. The possibility that the secondary component is a collapsed object is also discussed; the Copernicus observations are consistent with the hypothesis that the spectroscopically invisible secondary component is a black hole.

Kondo, Y.↗
NASA NTRS1975

Major and trace element chemistry of Boulder 1 at Station 2, Apollo 17

Twenty-seven samples from Boulder 1 at Station 2 are analyzed for major and trace elements by atomic absorption spectrophotometry and neutron activation analysis. Two types of matrix and several types of clast materials are characterized on the basis of their chemistry. It is shown that one matrix type is a common material at the Apollo 17 site, while the other is probably exotic to that site. The most unusual clast materials found are coarse norite (an old rock no longer found in millimeter fragments at the site) and pigeonite basalt (possibly a highland volcanic rock). It is concluded that the boulder-forming process combined materials from at least two different localities or vertical strata.

Blanchard, D. P.↗
NASA NTRS1976

J, H, K photometry of 433 Eros and other asteroids

Results are reported for IR photometry of nine bright asteroids, including 433 Eros, which was conducted in the J, H, K, and (for Eros) L bands with an InSb photometer on the 1.3-m Kitt Peak telescope. It is found that the J-H and H-K color indices of all nine asteroids are slightly redder than those of the sun and that three C-type objects are somewhat redder in the same color indices than four S-types and an E-type. Eros is shown to have an unusually red J-K index; the shape of its IR spectral reflectance curve is attributed in part to the presence of the weak 2-micron pyroxene absorption band in the spectrum. The results show that JHK photometry is less diagnostic of asteroidal composition than higher-resolution IR spectrophotometry.

Chapman, C. R.↗
NASA NTRS1976

Physical properties of asteroids from UBV photometry

A program of asteroid photoelectric photometry is discussed which is designed primarily to obtain UBV magnitudes and colors of most asteroids reaching magnitude 13.3 or brighter at opposition and of asteroids reaching magnitude 14.3 or brighter at perihelic opposition. A two-color plot is presented for asteroids whose compositional classes have been determined by radiometry, spectrophotometry, and polarimetry. A clear separation by color is observed for S and C objects; M and E objects are shown to be colorimetrically similar to C objects. Another two-color plot for about 200 asteroids reveals a continuum between the C and M, E domains and a possible continuum between the C and S domains. A plot of the frequency distribution of asteroid semimajor axes indicates that C objects predominate in the outer part of the asteroid belt while S objects are more numerous in the inner part. Statistics of asteroid phase angles and light-curve amplitudes are examined. It is suggested that the phase coefficient of an asteroid is inversely proportional to its geometric albedo and that S objects may be less spherical than C objects.

Bowell, E.↗
NASA NTRS1976

An extrasolar extreme-ultraviolet object. II - The nature of HZ 43

A variety of data are presented concerning the spectrum, distance, temperature, and evolutionary state of the hot white dwarf HZ 43, the first extrasolar object to be detected in the EUV band. The data include spectrophotometry of the star and its red dwarf companion (HZ 43B), a trigonometric parallax for the star, its tangential velocity, and results of soft X-ray and EUV observations. The main conclusions are that: (1) the spectrum of HZ 43A is that of a hot DAwk star, (2) HZ 43B is a dM3.5e star, (3) the distance of the system is about 65 pc, (4) the tangential velocity is not atypical of white dwarfs, and (5) the stellar energy distribution of HZ 43A is well fitted by a black body with an effective temperature of approximately 110,000 K. Evolutionary implications of the existence of an object as hot as HZ 43A are briefly considered, and it is suggested that the progenitors of hot DA stars must include objects hotter than spectral type sdB, with logical possibilities being nuclei of planetary nebulae and sdO stars.

Margon, B.↗
NASA NTRS1976

An intense extreme-ultraviolet source in Cetus

The detection of a second EUV (100-1000 A) probable white dwarf star with the EUV telescope aboard the Apollo Soyuz mission is reported. The positional error box includes Feige 24, a binary system consisting of a very blue white dwarf and a dMe star. A grid of LTE pure-hydrogen, high-surface-gravity model atmospheres, is used, in combination with the EUV data and optical spectrophotometry, to derive the stellar parameters, yielding an effective temperature of 60,000 K, a radius of 17,000 km at 100 pc, and a luminosity of 7(d/100 pc) squared solar luminosities. The Feige 24 models appear to rule out white dwarfs with pure hydrogen atmospheres if the interstellar helium abundance and ionization are not anomalous.

Margon, B.↗
NASA NTRS1977

The chemical composition of three planetary nebulae in the Magellanic Clouds

The paper studies the detailed spectral characteristics of the planetary nebulae N97 and N153 in the Large Magellanic Cloud (LMC), the planetary nebula N67 in the Small Magellanic Cloud (SMC), and the small H II regions N9, N61, and N81 in the SMC. Electron temperatures and densities for each nebula are derived from emission-line strengths determined by photographic spectrophotometry, and relative abundances are estimated for H, He, N, O, Ne, Ar, and S. The results show that: (1) N67 has a 60% overabundance in He/H while N97 and N153 have approximately normal He/H values; (2) all three planetaries have N/H values comparable to those of galactic planetaries but substantially higher than found in the H II regions of their respective Cloud; (3) the O/H values in the planetaries are similar to or lower than those in the H II regions of the respective Cloud; (4) the O/Ne, O/S, and O/Ar ratios in the two LMC planetaries are comparable to those in galactic planetaries; (5) the compositions of the small H II regions in the SMC are nearly identical to those of previously studied large H II regions in the same Cloud; and (6) the He/H ratio of the interstellar gas in the SMC is about 25% less than that in the Galaxy. It is concluded that most of the N abundance in both Clouds arose from nucleosynthesis sources other than planetary nebulae.

Dufour, R. J.↗
NASA NTRS1977

Observations of Jupiter and Saturn at 5-8 micron

Moderate-resolution spectrophotometry (about 0.015) has shown the effects of known atmospheric constituents (NH3, CH4, C2H6) on the 5-8 micron spectrum of Jupiter. Broadband observations of Saturn at 6.5 micron are also reported.

Russell, R. W.↗
NASA NTRS1977

Ultraviolet spectrum of quasi-stellar object 3C273

The first direct observation of the ultraviolet spectrum of a quasi-stellar object (QSO) has been made with a rocket-borne telescope. The emission line spectrum of 3C273 is similar to the spectra of high-redshift QSOs, but no absorption is observed. The results provide important new constraints on theoretical models of QSOs, place a severe limit on the density of neutral hydrogen in the intergalactic medium, and suggest a cosmological origin for much of the absorption seen in high-redshift QSOs. Comparison of the ultraviolet spectrophotometry of low- and high-redshift QSOs suggests that the universe is closed, with a deceleration parameter of about 1.

Davidsen, A. F.↗
NASA NTRS1977

Planetary astronomy program

A program was developed in which asteroids and two planets, namely, Saturn and Uranus, were investigated. This included: (1) asteroid spectrophotometry; (2) the nature of the Trojan asteroids; (3) an investigation to determine asteroid masses; (4) the photometry, structure, and dynamics of the rings surrounding the planet Saturn; and (5) aerosol distribution in the atmosphere of Uranus. Plans were finalized to obtain observations of the nucleus of the dying comet P/Arend-Rigaux. Further work was accomplished in asteroid data reduction. Data were entered into the TRIAD data file and a program generated classifications for over 560 different asteroids. A photoelectric area scanner was used to obtain UBV scans of the disk of the planet Saturn on several winter and spring nights in 1977. Intensity profiles show pronounced limb brightening in U, moderate limb brightening in B, and limb darkening in V. Narrow band photoelectric area-scanning photometry of the Uranus disk is also reported. Results are given.

Source record↗
NASA NTRS1977

Absolute calibration in the 1750 - 3350 A region

The absolute flux measurements in the rocket ultraviolet made by Bohlin, Frimout, and Lillie (BFL) are revised using a more correct treatment of the air extinction that enters the air calibration of their instrument. The absorption by molecular oxygen and ozone, Rayleigh scattering, and extinction by aerosols is tabulated for general use in ultraviolet calibrations performed in air. The revised absolute flux of eta UMa and final fluxes for alpha Lyr and zeta Oph are presented in the 1750-3350 A region. The absolute flux of the star eta UMa is compared to four other independent determinations in the 1200-3400 A region and a maximum difference of 35% is found near 1500 A between the OAO-2 and Apollo 17 fluxes. The rocket measurements of BFL, the ANS and TD-1 satellite data, and the Apollo 17 data are compared to the ultraviolet fluxes from the OAO-2, demonstrating a photometric reproducibility of about + or - 3 percent. Therefore, all four sets of spectrophotometry can be reduced to a common absolute scale.

Strongylis, G. J.↗
NASA NTRS1977

Infrared Observations of Late Type Stars

Substantive mass loss resulting in appreciable circumstellar dust envelopes is common in late-type stars. The evolutionary history and physical state of a cool star determine the chemistry within the outer stellar atmosphere mirrored by the molecular and particulate material present in the envelope. The observational consequences of this debris determined by moderate spectral resolution infrared spectrophotometry are reviewed. Significant information is provided by observations of the emergent energy flux of both the cool stellar photosphere and of the circumstellar dust envelope. The observation suggests that mass-loss occurs to some degree throughout late stellar evolutionary phases and that occasional periods of high mass loss are not uncommon.

Merrill, K. M.↗
NASA NTRS1978

Asteroid surface mineralogy: Evidence from earth-based telescope observations

The interpretation of asteroid reflectance spectrophotometry in terms of mineralogical types gives inferred mineral assemblages for about 60 asteroids. Asteroid surface materials are compared with similar materials that make up many meteorites. The absence of asteroids with spectra that match identically the ordinary chondrites is noted.

Mccord, T. B.↗
NASA NTRS1978

Infrared observations of asteroids from earth and space

Infrared reflectances at wavelength between 1 and 4 micrometers are used for determining asteroid surface mineralogy, surface composition, diameters, and albedos. Thermal models were developed for analyzing infrared observations at longer wavelengths. The discovery of a spectral feature due to water of hydration on Ceres seems to contradict the mineralogy inferred from spectrophotometry.

Matson, D. L.↗
NASA NTRS1978

The role of earth-based observations of asteroids during the next decade

Present reconnaissance studies of asteroids shift ground based programs to more specialized, intensive studies of selected individual bodies and special classes. Two powerful techniques--radar and mid-IR spectroscopy--have yet to be widely applied to asteroids; high priority should be given to: (1) search programs with a large Schmidt telescope (especially for Mars- and Earth-approaching bodies); (2) a moderate resolution visible and near-IR spectrophotometric survey of at least half the asteroids; (3) high resolution spectrophotometry and radiometry of unusual objects; (4) radar studies of representative main belt asteroids; and (5) application of the full complement of astrophysical techniques to objects of high scientific interest and to potential space mission targets. The infrared astronomical satellite also has high potential for contributing to asteroid science.

Chapman, C. R.↗
NASA NTRS1977

Ultraviolet observations of 3C 273 by the ANS

Five-band spectrophotometry between rest wavelengths of 1340 A and 2850 A is presented. The 2200-A absorption feature seems to be present in 3C 273 with a depth appropriate for an internal reddening of E(B-V) = 0.13. The dereddened ultraviolet flux distribution can be described by a power law of spectral index 1.21. This power law can account for the observed flux in X-rays. It provides more photons than needed to excite the observed H-beta by photoionization and Fe II lines by resonance fluorescence. The emission-line flux ratios, Ly-alpha/C IV/ semiforbidden C III/H-beta are 100/80/60/10.

Wu, C.-C.↗
NASA NTRS1977

Photometry of slow X-ray pulsars. II - The 13.9 minute period of X Persei

Results are presented for time-resolved narrow-band photometry and spectrophotometry of X Per performed in an unsuccessful effort to confirm previously reported observations of 13.9-min pulsations in the intensity of the He II line at 4686 A. No features that are synchronous with a 13.9-min period are found in the optical data, and simultaneous X-ray observations of 3U 0352+30 are reported which show that a strong 13.9-min X-ray modulation was present during the optical photometry. Some implications of the X-ray periodicities observed for X Per are considered.

Margon, B.↗