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  • Astrophysics  (9)
  • Aircraft Design, Testing and Performance
  • GEOPHYSICS
  • 2015-2019  (10)
  • 1965-1969
  • 2019  (5)
  • 2017  (5)
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  • 2015-2019  (10)
  • 1965-1969
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  • 1
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    Multimessenger Science Opportunities with mHz Gravitational Waves (2019)
    In:  CASI
    Details
    Publication Date: 2019-07-20
    Description: LISA will open the mHz band of gravitational waves (GWs) to the astronomy community. Thestrong gravity which powers the variety of GW sources in this band is also crucial in a numberof important astrophysical processes at the current frontiers of astronomy. These range fromthe beginning of structure formation in the early universe, through the origin and cosmic evolutionof massive black holes in concert with their galactic environments, to the evolution ofstellar remnant binaries in the Milky Way and in nearby galaxies. These processes and theirassociated populations also drive current and future observations across the electromagnetic(EM) spectrum. We review opportunities for science breakthroughs, involving either direct coincidentEM+GW observations, or indirect multimessenger studies. We argue that for the UScommunity to fully capitalize on the opportunities from the LISA mission, the US efforts shouldbe accompanied by a coordinated and sustained program of multi-disciplinary science investment,following the GW data through to its impact on broad areas of astrophysics. Supportfor LISA-related multimessenger observers and theorists should be sized appropriately for aflagship observatory and may be coordinated through a dedicated mHz GW research center.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN66947
    Format: application/pdf
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  • 2
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    Multiwavelength Characterization of an ACT-Selected, Lensed Dusty Star-Forming Galaxy at zeta 2.64 (2017)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: We present C I(21) and multi-transition C-12 O observations of a dusty star-forming galaxy, ACT J2029+0120,which we spectroscopically confirm to lie at zeta = 2.64. We detect CO(3-2), CO(5-4), CO(7-6), CO(8-7), and C I(2-1) at high significance, tentatively detect HCO+(4-3), and place strong upper limits on the integrated strength of dense gas tracers (HCN(4-3) and CS(7-6)). Multi-transition CO observations and dense gas tracers can provide valuable constraints on the molecular gas content and excitation conditions in high-redshift galaxies. We therefore use this unique data set to construct a CO spectral line energy distribution (SLED) of the source, which is most consistent with that of a ULIRG Seyfert or QSO host object in the taxonomy of the Herschel Comprehensive ULIRG Emission Survey. We employ RADEX models to fit the peak of the CO SLED, inferring a temperature of T approximately 117 K and n(sub H2) approximately 10(exp5) cm(exp -3), most consistent with a ULIRGQSO object and the presence of high-density tracers. We also find that the velocity width of the C I line is potentially larger than seen in all CO transitions forth is object, and that the L'(sub Ci(2-1))/L'(sub CO(3-2))ratio is also larger than seen in other lensed and unlensed submillimeter galaxies and QSO hosts; if confirmed, this anomaly could be an effect of differential lensing of a shocked molecular outflow.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN46867 , The Astrophysical Journal (ISSN 0004-637X) (e-ISSN 1538-4357); 844; 2; 110
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  • 3
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    Bayesian Treatment of Prospective LISA Parameter Estimation for Massive Black Hole Mergers (2017)
    In:  Other Sources
    Details
    Publication Date: 2019-07-27
    Description: A full understanding of LISA (Laser Interferometer Space Antenna)'s science capability will require accurate models of incident waveform signals and the instrumental response. While Fisher matrix analysis is useful for some estimates, a full Bayesian treatment is needed for important cases at the limit of LISA's capability. We will apply fast analysis algorithms enabling accurate treatment with EOB (effective-one-body) waveforms and the full-featured LISA response to study the significance of higher spherical harmonics and mergers in LISA analysis.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN56728 , International LISA (Laser Interferometer Space Antenna) Symposium; 5ý9 Sep. 2016; Zurich; Switzerland|Journal of Physics: Conference Series; 840; 1; 012051
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  • 4
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    Micrometeoroid Events in LISA Pathfinder (2019)
    In:  Other Sources
    Details
    Publication Date: 2019-11-30
    Description: The zodiacal dust complex, a population of dust and small particles that pervades the solar system, provides important insight into the formation and dynamics of planets, comets, asteroids, and other bodies. We present a new set of data obtained from direct measurements of momentum transfer to a spacecraft from individual particle impacts. This technique is made possible by the extreme precision of the instruments flown on the LISA Pathfinder spacecraft, a technology demonstrator for a future space-based gravitational wave observatory. Pathfinder employed a technique known as drag-free control that achieved rejection of external disturbances, including particle impacts, using a micropropulsion system. Using a simple model of the impacts and knowledge of the control system, we show that it is possible to detect impacts and measure properties such as the transferred momentum, direction of travel, and location of impact on the spacecraft. In this paper, we present the results of a systematic search for impacts during 4348 hr of Pathfinder data. We report a total of 54 candidates with transferred momenta ranging from 0.2 to 230 Ns. We furthermore make a comparison of these candidates with models of micrometeoroid populations in the inner solar system, including those resulting from Jupiter-family comets (JFCs), Oort Cloud comets, Halley-type comets, and asteroids. We find that our measured population is consistent with a population dominated by JFCs, with some evidence for a smaller contribution from Halley-type comets, in agreement with consensus models of the zodiacal dust complex in the momentum range sampled by LISA Pathfinder.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN75583 , Astrophysical Journal (ISSN 0004-637X) (e-ISSN 1538-4357); 883; 1; 53
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  • 5
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    The NANOGrav 11 Yr Data Set: Limits on Gravitational Waves from Individual Supermassive Black Hole Binaries (2019)
    In:  Other Sources
    Details
    Publication Date: 2019-12-31
    Description: Observations indicate that nearly all galaxies contain supermassive black holes at their centers. When galaxies merge, their component black holes form SMBH binaries (SMBHBs), which emit low-frequency gravitational waves (GWs) that can be detected by pulsar timing arrays. We have searched the North American Nanohertz Observatory for Gravitational Waves 11 yr data set for GWs from individual SMBHBs in circular orbits. As we did not find strong evidence for GWs in our data, we placed 95% upper limits on the strength of GWs from such sources. At f(gw) = 8 nHz, we placed a sky-averaged upper limit of h(0) 〈 7.3(3) 10(exp 15). We also developed a technique to determine the significance of a particular signal in each pulsar using "dropout" parameters as a way of identifying spurious signals. From these upper limits, we ruled out SMBHBs emitting GWs f(gw) = 8 nHz within 120 Mpc for M = 10(exp 9) Solar Mass, and within 5.5 Gpc for M= 10(exp 10) Solar Mass at our most sensitive sky location. We also determined that there are no SMBHBs with M 〉 1.6 x 10(exp 9) Solar Mass emitting GWs with f(gw) = 2.8317.8 nHz in the Virgo Cluster. Finally, we compared our strain upper limits to simulated populations of SMBHBs, based on galaxies in the Two Micron All-Sky Survey and merger rates from the Illustris cosmological simulation project, and found that only 34 out of 75,000 realizations of the local universe contained a detectable source.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN76492 , Astrophysical Journal; 880; 2; 116
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  • 6
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    Space Based Gravitational Wave Astronomy Beyond LISA (2019)
    In:  CASI
    Details
    Publication Date: 2019-08-09
    Description: The Laser Interferometer Space Antenna (LISA) will open three decades of gravitational wave(GW) spectrum between 0.1 and 100 mHz, the mHz band [1]. This band is expected to be the richest part of the GW spectrum, in types of sources, numbers of sources, signal-to-noise ratios and discovery potential. When LISA opens the low-frequency window of the gravitational wave spectrum,around 2034, the surge of gravitational-wave astronomy will strongly compel a subsequent mission to further explore the frequency bands of the GW spectrum that can only be accessed from space. The 2020's is the time to start developing technology and studying mission concepts for a large-scale mission to be launched in the 2040's. The mission concept would then be proposed to Astro2030. Only space-based missions can access the GW spectrum between 108 and 1 Hz because of the Earth's seismic noise. This white paper surveys the science in this band and mission concepts that could accomplish that science. The proposed small scale activity is a technology development program that would support a range of concepts and a mission concept study to choose a specific mission concept for Astro2030. In this white paper, we will refer to a generic GW mission beyond LISA as bLISA.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN70893
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  • 7
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    Building a Field: The Future of Astronomy with Gravitational Waves (2019)
    In:  CASI
    Details
    Publication Date: 2019-08-09
    Description: Harnessing the sheer discovery potential of GW Astronomy will require bold, deliberate,and sustained efforts to train and develop the requisite workforce. The next decaderequires a strategic plan to build - from the ground up - a robust, open, andwell-connected GW Astronomy community with deep participation from traditionalastronomers, physicists, data scientists, and instrumentalists. This basic infrastructure issorely needed as an enabling foundation for research. We outline a set ofrecommendations for funding agencies, universities, and professional societies to helpbuild a thriving, diverse, and inclusive new field.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN70892
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  • 8
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    SpaRibs Geometry Parameterization for Wings with Multiple Sections using Single Design (2017)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The SpaRibs topology of an aircraft wing has a significant effect on its structural behavior and stability as well as the flutter performance. The development of additive manufacturing techniques like Electron Beam Free Form Fabrication (EBF3) has made it feasible to manufacture aircraft wings with curvilinear spars, ribs (SpaRibs) and stiffeners. In this article a new global-local optimization framework for wing with multiple sections using curvilinear SpaRibs is described. A single design space is used to parameterize the SpaRibs geometry. This method has been implemented using MSC-PATRAN to create a broad range of SpaRibs topologies using limited number of parameters. It ensures C0 and C1 continuities in SpaRibs geometry at the junction of two wing sections with airfoil thickness gradient discontinuity as well as mesh continuity between all structural components. This method is advantageous in complex multi-disciplinary optimization due to its potential to reduce the number of design variables. For the global-local optimization the local panels are generated by an algorithm which is totally based on a set algebra on the connectivity matrix data. The great advantage of this method is that it is completely independent of the coordinates of the nodes of the finite element model. It is also independent of the order in which the elements are distributed in the FEM. The code is verified by optimizing of the CRM Baseline model at trim condition at Mach number equal to 0.85 for five different angle of attack (-2deg, 0deg,2deg,4deg and 6deg). The final weight of the wing is 19,090.61 lb. This value is comparable to that obtained by Qiang et al. 6 (19,269 lb).
    Keywords: Aircraft Design, Testing and Performance
    Type: AFRC-DAA-TN37932 , AIAA SciTech 2017; Jan 09, 2017 - Jan 13, 2017; Grapevine, TX; United States
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  • 9
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    Prompt Electromagnetic Transients from Binary Black Hole Mergers (2017)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Binary black hole (BBH) mergers provide a prime source for current and future interferometric gravitational wave observatories. Massive BBH mergers may often take place in plasma-rich environments, leading to the exciting possibility of a concurrent electromagnetic (EM) signal observable by traditional astronomical facilities. However, many critical questions about the generation of such counterparts remain unanswered. We explore mechanisms that may drive EM counterparts with magnetohydrodynamic simulations treating a range of scenarios involving equal-mass black-hole binaries immersed in an initially homogeneous fluid with uniform, orbitally aligned magnetic fields. We find that the time development of Poynting luminosity, which may drive jetlike emissions, is relatively insensitive to aspects of the initial configuration. In particular, over a significant range of initial values, the central magnetic field strength is effectively regulated by the gas flow to yield a Poynting luminosity of 1 0 Exp 45) 10(exp 46) (sub 13) M(sub 8)(exp 2) erg s(exp 1), with BBH mass scaled to M(sub 8) M / ( 10 8 M ) and ambient density 13 / ( 10(exp 13) g cm(sub 3)). We also calculate the direct plasma synchrotron emissions processed through geodesic ray-tracing. Despite lensing effects and dynamics, we find the observed synchrotron flux varies little leading up to merger.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN54261 , Physical Review D - Particles, Fields, Gravitation and Cosmology (ISSN 1550-7998) (e-ISSN 1550-2368); 96; 12; 123003
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  • 10
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    Prompt Electromagnetic Transients from Binary Black Hole Mergers (2017)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Binary black hole (BBH) mergers provide a prime source for current and future interferometric GW observatories. Massive BBH mergers may often take place in plasma-rich environments, leading to the exciting possibility of a concurrent electromagnetic (EM) signal observable by traditional astronomical facilities. However, many critical questions about the generation of such counterparts remain unanswered. We explore mechanisms that may drive EM counterparts with magnetohydrodynamic simulations treating a range of scenarios involving equal-mass black-hole binaries immersed in an initially homogeneous fluid with uniform, orbitally aligned magnetic fields. We find that the time development of Poynting luminosity, which may drive jet-like emissions, is relatively insensitive to aspects of the initial configuration. In particular, over a significant range of initial values, the central magnetic field strength is effectively regulated by the gas flow to yield a Poynting luminosity of 10(exp 45) - 10(exp 46) (p-13) M(sub 8)(exp 2) erg/s, with BBH mass scaled to M(sub 8) defined to be equal to M=(10(exp 8) solar mass) and ambient density p -13 defined to be equal to p/(10(exp -13) g/cu.cm). We also calculate the direct plasma synchrotron emissions processed through geodesic ray-tracing. Despite lensing effects and dynamics, we find the observed synchrotron flux varies little leading up to merger.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN51364 , Physical Review D - Particles, Fields, Gravitation and Cosmology (ISSN 1550-7998) (e-ISSN 1550-2368); 96; 12; 123003
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