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  • 1
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    Ultraviolet Imaging Telescope images of the reflection nebula NGC 7023 - Derivation of ultraviolet scattering properties of dust grains (1992)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: The Ultraviolet Imaging Telescope as part of the Astro-1 mission, was used to obtain high-resolution surface brightness distribution data in six ultraviolet wavelength bands for the bright reflection nebula NGC 7023. From the quantitative comparison of the measured surface brightness gradients ratios of nebular to stellar flux, and detail radial surface brightness profiles with corresponding data from the visible, two major conclusions results: (1) the scattering in the near- and far-ultraviolet in this nebula is more strongly forward-directed than in the visible; (2) the dust albedo in the ultraviolet for wavelengths not less than 140 nm is identical to that in the visible, with the exception of the 220 nm bump in the extinction curve. In the wavelengths region of the bump, the albedo is reduced by 25 to 30 percent in comparison with wavelengths regions both shorter and longer. This lower albedo is expected, if the bump is a pure absorption feature.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 395; 1; p. L5-L8.
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  • 2
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    Astro-1 ultraviolet imaging of the 30 Doradus and SN 1987A fields with the Ultraviolet Imaging Telescope (1992)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: A preliminary analysis of Ultraviolet Imaging Telescope (UIT) images in the 30 Doradus region is reported. Photometry was obtained for the 30 Doradus cluster and its UV-bright core, R136, in various UIT bandpasses. It is found that about 14 percent of the total FUV light and about 16 percent of the total near-UV light of the 3-arcmin diameter 30 Doradus cluster originates from the region within 5 arcsec of R136. The UV magnitudes and colors of R136 and other known O and Wolf-Rayet WN stars in the same field were measured. The UIT data, combined with published observations at longer wavelengths, indicate that R136a1, the brightest component of R136, is not a supermassive stars. A qualitative comparison between the UIT images, Einstein X-ray data, IRAS HiRes images, and ground-based CCD images in forbidden O III 5007 A, H-alpha, B, R, U, and Stromgren u is performed. The extended diffuse UV feature detected in the UIT images is correlated with the IR structure seen in the IRAS 60-micron HiRes image, which suggests the existence of large amounts of widely distributed dust in this region.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 395; 1; p. L29-L32.
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  • 3
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    Ultraviolet spectroscopy of the 'jetlike' condensations of NGC 4151 (1988)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The spectrometers aboard the IUE are used to obtain UV spectroscopy of the jetlike condensations seen extending 18 arcsec from the nucleus of the nearby Seyfert 1 galaxy NGC 4151. New data reduction techniques are used to detect, delineate, and measure weak nebular emission in IUE spectra. Spatially resolved extended emission is seen in both semiforbidden C III 1909 A and C IV 1549 A. The deduced integrated fluxes in the jet are 10 to the 14th and 4 x 10 to the 14th ergs/sq cm/s for C III and C IV, respectively. The observed fluxes are compared with predictions based upon a central source photoionization model. The implied high C IV/C III flux ratio is shown to be inconsistent with this model and suggests an additional source of ionization for the jet.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 327; 664-670
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  • 4
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    IUE spectra of HD 269665 (Sk -68 deg 110), a hot subdwarf in the direction of the Large Magellanic Cloud (1989)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Comparison of high- and low-resolution IUE spectra of HD 269665 (Sanduleak -68 deg 110) show that the star is a subdwarf with a temperature in the range 30,000-50,000 K. The visual spectrum shows Balmer lines and weak He II 4686 A lines. Balmer-line width and a fit of the UV-visual flux distribution using the Blackwell-Shallis (1977) algorithm yields an effective temperature between 30,000 and 38,000 K and log g = 5-6. A table is presented of photospheric UV spectral lines in HD 269665. The radial velocity of the star is found to be 5.8 + or - 0.5 km/s.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal (ISSN 0004-6256); 97; 881-890
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  • 5
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    Vacuum ultraviolet images of the Large Magellanic Cloud (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Linearized, absolutely calibrated VUV images of the LMC with a resolution of about 50 arcsec are presented. The images were made by a sounding rocket payload in two bandpasses with effective wavelengths for hot stars near 1500 A and 1930 A. The flux in each bandpass is measured for the associations in the list of Lucke and Hodge (1970). The results are discussed and their relationship to the overall characteristics of star formation in the LMC are discussed. A simple model for propagating star formation in the LMC is presented whose results closely resemble the distribution of associations revealed by the VUV images.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 320; 609-625
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  • 6
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    Validation of Measured Damping Trends for Flight-Like Vehicle Panel/Equipment including a Range of Cable Harness Assemblies (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-27
    Description: This validation study examines the effect on vibroacoustic response resulting from the installation of cable bundles on a curved orthogrid panel. Of interest is the level of damping provided by the installation of the cable bundles and whether this damping could be potentially leveraged in launch vehicle design. The results of this test are compared with baseline acoustic response tests without cables. Damping estimates from the measured response data are made using a new software tool that leverages a finite element model of the panel in conjunction with advanced optimization techniques. While the full test series is not yet complete, the first configuration of cable bundles that was assessed effectively increased the viscous critical damping fraction of the system by as much as 0.02 in certain frequency ranges.
    Keywords: Launch Vehicles and Launch Operations
    Type: M11-0878 , M12-1663 , 53rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference 2012; Apr 23, 1012 - Apr 26, 1012
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  • 7
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    Star formation in NGC 4449: MAMA-detector UV imagery and Fabry-Perot Balmer-line imagery (1994)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Using far-ultraviolet (FUV) and Balmer-line imagery, we investigate the star formation history of 22 large OB complexes in the Magellanic irregular galaxy NGC 4449. The FUV luminosity of NGC 4449 is comparable to those of late-type spirals and is greater than that of the LMC by approximately 2.4 mag, indicating substantial star formation in the last 10(exp 8) yr. FUV data were taken using a sounding-rocket telescope with a Multianode Microchannel Array (MAMA) detector, and Balmer-line data were taken using the Goddard Fabry-Perot Imager. The resulting imagery shows bright, roughly coincident FUV and H alpha sources throughout the extent of the visible galaxy. We model these sources using cluster-evolution codes. Although all sources are a few Myr old, clear age differences are found. In particular, several of the most recently active star formation regions are located together in the galaxy's northern periphery, which is apparently coincident with a large H I reservoir. The brightest and most massive OB complexes are found along the northeast-southwest surface brightness ridgeline (the 'bar'). Over the entire galaxy, star formation rates are consistent on timescales of 10(exp 6), 10(exp 8), and 10(exp 9) yr. A history of recent star formation is suggested with two main episodes, one predominantly in the bar ending approximately 5 Myr ago, and an ongoing one associated with an observed H I cloud.
    Keywords: ASTROPHYSICS
    Type: The Astrophysical Journal (ISSN 0004-637X); 430; 2 pt; p. 568-580
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  • 8
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    Resolution of Forces and Strain Measurements from an Acoustic Ground Test (2013)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The Conservatism in Typical Vibration Tests was Demonstrated: Vibration test at component level produced conservative force reactions by approximately a factor of 4 (approx.12 dB) as compared to the integrated acoustic test in 2 out of 3 axes. Reaction Forces Estimated at the Base of Equipment Using a Finite Element Based Method were Validated: FEM based estimate of interface forces may be adequate to guide development of vibration test criteria with less conservatism. Element Forces Estimated in Secondary Structure Struts were Validated: Finite element approach provided best estimate of axial strut forces in frequency range below 200 Hz where a rigid lumped mass assumption for the entire electronics box was valid. Models with enough fidelity to represent diminishing apparent mass of equipment are better suited for estimating force reactions across the frequency range. Forward Work: Demonstrate the reduction in conservatism provided by; Current force limited approach and an FEM guided approach. Validate proposed CMS approach to estimate coupled response from uncoupled system characteristics for vibroacoustics.
    Keywords: Acoustics
    Type: M13-2669 , Spacecraft and Launch Vehicle Dynamic Environments Workshop; Jun 04, 2013 - Jun 06, 2013; El Segundo, CA; United States
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  • 9
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    Reporting Recommended Patch Density from Vehicle Panel Vibration Convergence Studies using both DAF and TBL Fits of the Spatial Correlation Function (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Using the patch method to represent the continuous spatial correlation function of a phased pressure field over a structural surface is an approximation. The approximation approaches the continuous function as patches become smaller. Plotting comparisons of the approximation vs the continuous function may provide insight revealing: (1) For what patch size/density should the approximation be very good? (2) What the approximation looks like when it begins to break down? (3) What the approximation looks like when the patch size is grossly too large. Following these observations with a convergence study using one FEM may allow us to see the importance of patch density. We may develop insights that help us to predict sufficient patch density to provide adequate convergence for the intended purpose frequency range of interest
    Keywords: Acoustics
    Type: M12-1883 , Spacecraft and Launch Vehicle Dynamics Environments Workshop; Jun 19, 2012 - Jun 21, 2012; El Segundo, CA; United States
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  • 10
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    Determining System Response using Uncoupled Transfer Functions - And Advantages Using Response Matching Methods (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: No abstract available
    Keywords: Acoustics
    Type: M12-1885 , Spacecraft and Launch Vehicle Dynamics Environments Workshop; Jun 19, 2012 - Jun 21, 2012; El Segundo, CA; United States
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