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  • 1
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    Trace-element composition of Chicxulub crater melt rock, K/T tektites and Yucatan basement (1993)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The Cretaceous/Tertiary (K/T) boundary Chicxulub impact is the best preserved large impact in the geologic record. The Chicxulub crater has been buried with no apparent erosion of its intracrater deposits, and its ejecta blanket is known and is well preserved at hundreds of localities globally. Although most of the molten material ejected from the crater has been largely altered, a few localities still preserve tektite glass. Availability of intra- and extracrater impact products as well as plausible matches to the targeted rocks allows the comparison of compositions of the different classes of impact products to those of the impacted lithologies. Determination of trace-element compositions of the K/T tektites, Chicxulub melt rock, and the targeted Yucatan silicate basement and carbonate/evaporite lithologies have been made using instrumental neutron activation analysis (INAA) and inductively coupled plasma mass spectrometry (ICP-MS). Some sample splits were studied with both techniques to ensure that inter-laboratory variation was not significant or could be corrected. The concentration of a few major and minor elements was also checked against microprobe results. Radiochemical neutron activation analysis (RNAA) was used to determine Ir abundances in some samples.
    Keywords: ASTROPHYSICS
    Type: Lunar and Planetary Inst., Twenty-Fourth Lunar and Planetary Science Conference. Part 2: G-M; p 657-658
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  • 2
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    Experimental constraints on the origin of chondrules (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Chrondule formation was an important (perhaps ubiguitous) process in the early solar system, yet their origins remain elusive. Some points, however, are clear. The precursor material of chondules (dust) was rapidly heated at rates of perhaps thousands of degrees per second and was cooled more slowly. It was proposed to investigate chondrule formation in the Space Station environment via a dust-box (a chamber in which dust can be suspended, heated, and cooled. A microgravity environment is conducive to this kind of experiment because of the significant retardation of settling rates compared with a terrestrial laboratory environment. These long-duration experiments might require the development of technologies to counteract even the small, but finite and permanent gravitation field of the Space Station. Simple, but interesting experiments on dust suspensions immediately present themselves.
    Keywords: ASTROPHYSICS
    Type: NASA, Lyndon B. Johnson Space Center, Experiments in Planetary and Related Sciences and the Space Station; 2 p
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  • 3
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    The magnetic field structure in high-mass star formation regions (1995)
    In:  Other Sources
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    Publication Date: 2013-08-29
    Description: We present a preliminary analysis of far-IR polarimetric observations, which were made to study the magnetic field structure in the high-mass star formation regions of M42, NGC2024, and W3. These observations were made from the Kuiper Airborne Observatory (KAO), using the University of Chicago far-IR polarimeter, Stokes.
    Keywords: ASTROPHYSICS
    Type: Astronomical Society of the Pacific, Airborne Astronomy Symposium on the Galactic Ecosystem: From Gas to Stars to Dust, Volume 73; p 225-234
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  • 4
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    Submillimeter observations of evolved stars (1985)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Broadband submillimeter observations of thermal emission from several evolved stars have been obtained using the United Kingdom Infrared Telescope on Mauna Kea, Hawaii. The observations were carried out at an effective wavelength of 400 microns in order to estimate the mass loss rates in dust from the stars. Direct estimates of mass loss rates are in the range 10 to the -9th to 10 to the -6th solar mass/yr. Analysis of the spectrum of IRC + 10216 confirmed previous estimates of dust grain emissivity in the range 10-1000 microns. The infrared properties of IRC + 10216 are found to be similar to the carbon rich object CRL 3068. No systematic difference was found between the dust masses of carbon rich and oxygen rich envelopes. The largest mass loss rates in dust were obtained for the bipolar objects OH 231.8 + 4.2 CRL 2688, CRL 618, and NGC 7027. It is suggested that the ratios of gas to dust, and the slopes of the far infrared to submillimeter wavelength continua of these stars objects are probably representative of amorphous rather than crystalline grains.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 294; 242-255
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  • 5
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    The evolution of rapid oscillations in an outburst of a dwarf nova (1980)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: High-speed photometric observations of the dwarf nova AH Her on nine consecutive days during an outburst have been made, and rapid coherent oscillations on every day except two near maximum light have been detected. The period, amplitude, and luminosity for each day is presented and the progression of the periods is discussed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 238
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  • 6
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    The color of the fast oscillations of AH Herculis (1981)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The color of the fast coherent oscillations of AH Herculis is measured by comparing simultaneous records of the photon arrival rate in two wavelength bands, 355 + or - 30 nm and 795 + or - 80 nm. It is found that the color temperature of the coherent oscillation detected in these two wavelength bands is between 28,000 and 73,000 K. The color temperature of the nonoscillating luminosity is much lower. The arrival times of photons in these two bands have also been correlated, and it is found that the time interval between the long-wavelength coherent signal and the ultraviolet coherent signal is 0.26 + or - 0.5 sec. These results suggest that it is the surface of the white dwarf or the hot inner portion of the accretion disk which is emitting the coherent signal. The oscillations become detectably incoherent at the approach to minimum light after the outburst, as would be expected if the oscillating medium becomes more dissipative as it cools, or if there were increased modulation by clouds of obscuring material.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 248
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  • 7
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    Detection of submillimeter polarization in the Orion nebula (1984)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Linear polarization has been observed in the submillimeter radiation (270 microns) from two regions of Orion: one centered in the Kleinmann-Low nebula and one centered 1.5 arcmin south of the nebula. The observations were performed in September of 1983 and January of 1984 with the NASA Kuiper Airborne Observatory (KAO). The polarizations measured for the two regions were both 1.7 percent, plus or minus 0.4 and 0.5 percent, respectively. The angle of the outflow from both sources was 27 degrees, plus or minus seven degrees. An upper limit for polarization in the submillimeter radiation from the nebula W3(OH) was established at 1.6 percent. The observational data are compared with results from several other recent polarimetric observations of Orion, and some of their implications are discussed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 284; L51-L54
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  • 8
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    Far-infrared and submillimeter observations of the multiple cores in S255, W3, and OMC-1 - Evidence for fragmentation? (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The two cores of the S255 cloud were mapped at 60, 100, 185, and 400 microns and 40-400 microns maps were made of the cores and S255, OMC-1 and W3. Absolute flux densities were determined with an accuracy of 30 percent. The luminosities and masses of the S255 cores were equivalent to those of the other objects, including the concentration of a compact H II region around young objects. The densified regions are regarded as typical of areas where massive objects are forming. The observed 1.4-4 km/sec velocity differences between two cores in any one cloud indicates that the angular momentum of the original clouds, which drove the collapse of the cores, is transferred to the massive young stars.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 284; 637-642
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  • 9
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    Far-infrared properties of dust in the reflection nebula NGC 7023 (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Thermal emission from dust in the reflection nebula NGC 7023 has been observed at wavelengths between 40 and 400 microns. The observed far-infrared emission comes from a region approximately 4 arcmin in diameter and shows spatial structure which correlates well with the distribution of reflected visible radiation. Temperature and optical depth maps indicate that the dust which emits the far-infrared radiation is heated by UV and visual radiation from the central star (HD 200775) and that the dust density increases steeply northwest of the star. The far-infrared data are not consistent with either the spherical or uniform slab geometries used in earlier analyses of optical observations. Comparisons of the far-infrared measurements with optical and UV measurements give a value between 2000 and 5000 for the ratio of extinction efficiency in the UV to that at 125 microns. This value is compared with the results of other observational studies and with theoretical grain models.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 246
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  • 10
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    Far-infrared selected star formation regions (1984)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Detailed far-IR observations and complementary submillimeter, 5 GHz continuum and C(O-18) observations of a sample of eight far-IR selected luminous regions of star formation are presented. The observations show that the sources of luminosity coincide with density peaks in the molecular clouds and that the exciting stars lie deep within these condensations. The far-IR sources have diversely shaped 40-180 micron spectra even though their 60-100 micron color temperatures are similar. The radio and far-IR results together show that the exciting stars are in clusters containing either zero-age main-sequence and pre-main-sequence stars or consisting entirely of pre-main-sequence objects. C(O-18) and submillimeter observations imply gas densities approximately 100,000-high enough to make T(dust) approximately T(gas).
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 281; 225-236
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