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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS2013

Candels Multi-Wavelength Catalogs: Source Detection and Photometry in the Goods-South Field

We present a UV to mid-infrared multi-wavelength catalog in the CANDELS/GOODS-S field, combining the newly obtained CANDELS HST/WFC3 F105W, F125W, and F160W data with existing public data. The catalog is based on source detection in the WFC3 F160W band. The F160W mosaic includes the data from CANDELS deep and wide observations as well as previous ERS and HUDF09 programs. The mosaic reaches a 5σ limiting depth (within an aperture of radius 0farcs17) of 27.4, 28.2, and 29.7 AB for CANDELS wide, deep, and HUDF regions, respectively. The catalog contains 34,930 sources with the representative 50% completeness reaching 25.9, 26.6, and 28.1 AB in the F160W band for the three regions. In addition to WFC3 bands, the catalog also includes data from UV (U band from both CTIO/MOSAIC and VLT/VIMOS), optical (HST/ACS F435W, F606W, F775W, F814W, and F850LP), and infrared (HST/WFC3 F098M, VLT/ISAAC Ks, VLT/HAWK-I Ks, and Spitzer/IRAC 3.6, 4.5, 5.8, 8.0 μm) observations. The catalog is validated via stellar colors, comparison with other published catalogs, zero-point offsets determined from the best-fit templates of the spectral energy distribution of spectroscopically observed objects, and the accuracy of photometric redshifts. The catalog is able to detect unreddened star-forming (passive) galaxies with stellar mass of 10(exp 10) M(sub ☉) at a 50% completeness level to z ~ 3.4 (2.8), 4.6 (3.2), and 7.0 (4.2) in the three regions. As an example of application, the catalog is used to select both star-forming and passive galaxies at z ~ 2-4 via the Balmer break. It is also used to study the color-magnitude diagram of galaxies at 0 < z < 4.

CATALOGS↗
NASA NTRS2019

Implications of the Warm Corona and Relativistic Reflection Models for the Soft Excess in Mrk 509

We present the analysis of the first Nuclear Spectroscopic Telescope Array observations (∼220 ks), simultaneous with the last Suzaku observations (∼50 ks), of the active galactic nucleus of the bright Seyfert 1 galaxy Mrk 509. The time-averaged spectrum in the 1–79 keV X-ray band is dominated by a power-law continuum (Γ ∼ 1.8–1.9), a strong soft excess around 1 keV, and signatures of X-ray reflection in the form of Fe K emission (∼6.4 keV), an Fe K absorption edge (∼7.1 keV), and a Compton hump due to electron scattering (∼20–30 keV). We show that these data can be described by two very different prescriptions for the soft excess: a warm (kT ∼ 0.5–1 keV) and optically thick (τ ∼ 10–20) Comptonizing corona or a relativistically blurred ionized reflection spectrum from the inner regions of the accretion disk. While these two scenarios cannot be distinguished based on their fit statistics, we argue that the parameters required by the warm corona model are physically incompatible with the conditions of standard coronae. Detailed photoionization calculations show that even in the most favorable conditions, the warm corona should produce strong absorption in the observed spectrum. On the other hand, while the relativistic reflection model provides a satisfactory description of the data, it also requires extreme parameters, such as maximum black hole spin, a very low and compact hot corona, and a very high density for the inner accretion disk. Deeper observations of this source are thus necessary to confirm the presence of relativistic reflection and further understand the nature of its soft excess.

Javier Garcia↗
NASA NTRS2021

Simultaneous Multiwavelength Flare Observations of EV Lacertae

We present the first results of our ongoing project conducting simultaneous multiwavelength observations of flares on nearby active M dwarfs. We acquired data of the nearby dM3.5e star EV Lac using five different observatories: NASA's Transiting Exoplanet Survey Satellite (TESS), NASA's Neil Gehrels Swift Observatory (Swift), NASA's Neutron Interior Composition Explorer (NICER), the University of Hawaii 2.2-meter telescope (UH88), and the Las Cumbres Observatory Global Telescope (LCOGT) Network. During the ∼25 days of TESS observations, we acquired three simultaneous UV/X-ray observations using Swift that total ∼18 ks, 21 simultaneous epochs totaling ∼98 ks of X-ray data using NICER, one observation (∼3 hr) with UH88, and one observation (∼3 hr) with LCOGT. We identified 56 flares in the TESS light curve with estimated energies in the range log E(T) (erg) = (30.5–33.2), nine flares in the Swift UVM2 light curve with estimated energies in the range log E(UV) (erg) = (29.3–31.1), 14 flares in the NICER light curve with estimated minimum energies in the range log E(N) (erg) = (30.5–32.3), and 1 flare in the LCOGT light curve with log E(L) (erg) = 31.6. We find that the flare frequency distributions (FFDs) of TESS and NICER flares have comparable slopes, β(T) = −0.67 ± 0.09 and β(N) = − 0.65 ± 0.19, and the FFD of UVOT flares has a shallower slope (β(U) = −0.38 ± 0.13). Furthermore, we do not find conclusive evidence for either the first ionization potential (FIP) or the inverse FIP effect during coronal flares on EV Lac.

Rishi R. Paudel↗
NASA NTRS2022

TESS Revisits WASP-12: Updated Orbital Decay Rate and Constraints on Atmospheric Variability

After observing WASP-12 in the second year of the primary mission, the Transiting Exoplanet Survey Satellite (TESS) revisited the system in late 2021 during its extended mission. In this paper, we incorporate the new TESS photometry into a reanalysis of the transits, secondary eclipses, and phase curve. We also present a new Ks-band occultation observation of WASP-12b obtained with the Palomar/Wide-field Infrared Camera instrument. The latest TESS photometry spans three consecutive months, quadrupling the total length of the TESS WASP-12 light curve and extending the overall time baseline by almost two years. Based on the full set of available transit and occultation timings, we find that the orbital period is shrinking at a rate of −29.81 ± 0.94 ms yr−1. The additional data also increase the measurement precision of the transit depth, orbital parameters, and phase-curve amplitudes. We obtain a secondary eclipse depth of 466 ± 35 ppm, a 2σ upper limit on the nightside brightness of 70 ppm, and a marginal 6°.2 ± 2°.8 eastward offset between the dayside hotspot and the substellar point. The voluminous TESS data set allows us to assess the level of atmospheric variability on timescales of days, months, and years. We do not detect any statistically significant modulations in the secondary eclipse depth or day–night brightness contrast. Likewise, our measured Ks-band occultation depth of 2810 ± 390 ppm is consistent with most ∼2.2 μm observations in the literature.

Ian Wong↗
NASA NTRS2014

The Architecture of the LkCa 15 Transitional Disk Revealed by High-contrast Imaging

We present four new epochs of Ks-band images of the young pre-transitional disk around LkCa 15, and perform extensive forward modeling to derive the physical parameters of the disk. We find indications of strongly anisotropic scattering (Henyey-Greenstein g = 0.67+0.18 −0.11) and a significantly tapered gap edge ('round wall'), but see no evidence that the inner disk, whose existence is predicted by the spectral energy distribution, shadows the outer regions of the disk visible in our images. We marginally confirm the existence of an offset between the disk center and the star along the line of nodes; however, the magnitude of this offset (x = 27+19 −20 mas) is notably lower than that found in our earlier H-band images (Thalmann et al. 2010). Intriguingly, we also find, at high significance, an offset of y = 69+49 −25 mas perpendicular to the line of nodes. If confirmed by future observations, this would imply a highly elliptical- or otherwise asymmetric-disk gap with an effective eccentricity of e ≈ 0.3. Such asymmetry would most likely be the result of dynamical sculpting by one or more unseen planets in the system. Finally, we find that the bright arc of scattered light we see in direct imaging observations originates from the near side of the disk, and appears brighter than the far side because of strong forward scattering.

anisotropic scattering↗
NASA NTRS2014

Measuring the Coronal Properties of IC 4329A with NuSTAR

We present an analysis of an approximately 160 ks NuSTAR observation of the nearby bright Seyfert galaxy IC 4329A. The highquality broadband spectrum enables us to separate the effects of distant reflection from the direct coronal continuum, and to therefore accurately measure the high-energy cutoff to be E(sub cut) = 178 (+74 / −40) keV. The coronal emission arises from accretion disk photons Compton up-scattered by a thermal plasma, with the spectral index and cutoff being due to a combination of the finite plasma temperature and optical depth. Applying standard Comptonization models, we measure both physical properties independently using the best signal to noise obtained to date in an active galactic nucleus over the 3 - 79 keV band. We derive kT(sub e) = 37(+7 /−6) keV with tau = 1.25(+0.20 / −0.10) assuming a slab geometry for the plasma, and kT(sub e) = 33(+6 / −6) keV with tau = 3.41(+0.58 / −0.38) for a spherical geometry, with both having an equivalent goodness-of-fit.

finite plasma temperature↗
NASA NTRS1971

Protective claddings for high strength chromium alloys

The application of a Cr-Y-Hf-Th alloy as a protective cladding for a high strength chromium alloy was investigated for its effectiveness in inhibiting nitrogen embrittlement of a core alloy. Cladding was accomplished by a combination of hot gas pressure bonding and roll cladding techniques. Based on bend DBTT, the cladding alloy was effective in inhibiting nitrogen embrittlement of the chromium core alloy for up to 720 ks (200hours) in air at 1422 K (2100 F). A significant increase in the bend DBTT occurred with longer time exposures at 1422 K or short time exposures at 1589 K (2400 F).

Collins, J. F.↗
NASA NTRS1972

Thermal conductivity of liquid InSb and liquid Ga.

The mean thermal conductivity of liquid gallium was measured as 70 (plus or minus 7) W/m/K over the range 250-550 C. For indium antimonide, Kl = 2.04Ks at the melting temperature with Kl = 9.23 W/m/K- as a reasonable absolute value.

Seidensticker, R. G.↗
NASA NTRS1975

Space LOX vent system

This is the final report summarizing the work completed under contract NAS8-26972. Concept selection, design, fabricating and testing of a prototype compact heat exchanger thermodynamic vent system are discussed. The system is designed to operate in a 2.7m (9 foot) spherical liquid oxygen tank with a heating rate of 32.2 - 35.2 watts (110-120 Btu/hr) and to control pressure to 310 + or - 13.8 kN/sq m (45 + or - 2.0 psia.) the design mission is of 2,590 ks (30 days) duration on board a space shuttle orbiter.

Erickson, R. C.↗
NASA NTRS1982

The hot components of hydrogen deficient binaries

Low resolution IUE observations of the hot components of three very similar but peculiar objects: LSS 4300, Upsilon Sgr, and KS Per were compared. The possible evolutionary scenarios from observations and the extremely low hydrogen contents of the visible stars are discussed. It is suggested that the hot secondaries in hydrogen deficient binaries should also be hydrogen deficient.

Drilling, J. S.↗
NASA NTRS1984

Failure of vincristine induce twinning

Mammalian ova do not contain axes of symmetry from which are derived embryonic axes of symmetry. Mammalian axis determination is an early embryologic event occurring at about the time that monozygous twinning in mice. (Kaufma MH & O'Shea KS, 1978, Nature 276:707) and an attempt was made to reproduce their work in several strains of mice. Over 3200 embryos were examined without any twins being found. To rule out the possibility that vincristine caused twinning plus some lethal malformation (with subsequent resorption of the embryo) the embryos were examined 36-60 hours after vincristine treatment.

Binder, M.↗
NASA NTRS1983

Geometry of spinor regularization

The Kustaanheimo theory of spinor regularization is given a new formulation in terms of geometric algebra. The Kustaanheimo-Stiefel matrix and its subsidiary condition are put in a spinor form directly related to the geometry of the orbit in physical space. A physically significant alternative to the KS subsidiary condition is discussed. Derivations are carried out without using coordinates.

Hestenes, D.↗
NASA NTRS1984

The Brownell and Ness County (1894) L6 chondrites - Further sorting-out of Ness County meteorites

Brownell is a new moderately shocked L6 chondrite from Ness County, KS, that is petrologically distinct from the other L6 chondrites from Ness County. These latter meteorites, Wellmanville, Franklinville, and Ness County (1894), are very similar in their olivine and low-Ca pyroxene compositional distributions, kamacite Co contents, modal abundances of metallic Fe, Ni, and presence of martensitic metallic Fe, Ni (about 14 wt pct Ni). However, their silicates indicate that they have been shocked to different extents. It is suggested that all three probably represent a single heterogeneously-shocked L6 fragmental breccia that fell over a large area over 30 km in length.

Rubin, A. E.↗
NASA NTRS1986

Relation between microstructural heterogeneous surface layer and nitrogen pressure during sintering in Si3N4-Ml2O3 ceramics

The effects of N2 pressure (0.1 to 50 MPa) during sintering on the thickness of the microstructurally heterogeneous layer (MHL) formed near the surface of the compact, transverse-rupture strength, were investigated for Si3N4-(10 to 20) mol % MgO-5.5 mol % Al2O3 ceramics. The sintering temperature and time were 1973 K and 3.6 ks, respectively. The N2 gas was introduced into the furnace at about 1273 K. When the compacts were sintered under a certain N2 pressure, for example, about 20 and 7 MPa for 10 and 15 mol% MgO, respectively, the evolutions of N and Si were suppressed. The thickness of the MHL became very small and at the same time the strength of the surface layer of the compact (which was normally less than that of the inside in the case of 0.1 MPa) became nearly the same value as that of the inside. At higher pressure, the strength of both surface layer and the inside decreased considerably. Some discussion was made on these results.

Hayashi, K.↗
NASA NTRS1988

Fully-coupled analysis of jet mixing problems. Three-dimensional PNS model, SCIP3D

Numerical procedures formulated for the analysis of 3D jet mixing problems, as incorporated in the computer model, SCIP3D, are described. The overall methodology closely parallels that developed in the earlier 2D axisymmetric jet mixing model, SCIPVIS. SCIP3D integrates the 3D parabolized Navier-Stokes (PNS) jet mixing equations, cast in mapped cartesian or cylindrical coordinates, employing the explicit MacCormack Algorithm. A pressure split variant of this algorithm is employed in subsonic regions with a sublayer approximation utilized for treating the streamwise pressure component. SCIP3D contains both the ks and kW turbulence models, and employs a two component mixture approach to treat jet exhausts of arbitrary composition. Specialized grid procedures are used to adjust the grid growth in accordance with the growth of the jet, including a hybrid cartesian/cylindrical grid procedure for rectangular jets which moves the hybrid coordinate origin towards the flow origin as the jet transitions from a rectangular to circular shape. Numerous calculations are presented for rectangular mixing problems, as well as for a variety of basic unit problems exhibiting overall capabilities of SCIP3D.

Wolf, D. E.↗
NASA NTRS1991

An integrated control/structure design method using multi-objective optimization

The benefits are demonstrated of a multiobjective optimization based control structure integrated design methodology. An application of the proposed CSI methodology to the integrated design of the Spacecraft COntrol Lab Experiment (SCOLE) configuration is presented. Integrated design resulted in reducing both the control performance measure and the mass. Thus, better overall performance is achieved through integrated design optimization. The mutliobjective optimization approach used provides Pareto optimal solutions by unconstrained minimization of a differentiable KS function. Furthermore, adjusting the parameters gives insight into the trade-offs involved between different objectives.

Gupta, Sandeep↗
NASA NTRS1990

Quasilinear saturation of forced current sheet tearing modes

Numerical studies of tearing modes in a nearly singular forced current sheet equilibrium (Liewer and Payne, 1990) show that the modes saturate quasilinearly when the width of the magnetic island formed by the reconnection is on the order of several times the linear mode width which scales as approximately (kS) exp -2/5, where S is the Lundquist number and k is the wavenumber. The modes saturate quasilinearly by flattening the current profile, converting magnetic energy into plasma energy. The longer wavelength modes, which saturate at higher levels, release the most energy. These modes may, nonlinearly, play a role in coronal heating when sharp current sheets form as a result of global magnetic stresses.

Liewer, Paulett C.↗
NASA NTRS1990

Net radiation, sensible and latent heat flux densities on slopes computed by the energy balance method

Energy balance components obtained over five grass-covered sloping surfaces near Manhattan, KS, using the Bowen ratio energy balance technique with the instruments mounted horizontally were compared with calculated values when the instruments were mounted parallel to the surfaces. Hourly values of the components changed when the instruments were parallel to the surfaces. The changes were larger at low solar angles (spring and fall) and on steeper slopes. An area average of daylight totals, assuming that all aspects were equally represented, changed only 0.1 percent on June 6 and 2.3 percent on October 11. The calculations, extended to steeper slopes, indicated small changes in the daylight totals for slopes of less than 10 deg.

Fritschen, Leo↗