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  • Other Sources  (3)
  • 2005-2009  (3)
  • 2000-2004
  • 2009  (3)
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  • 2005-2009  (3)
  • 2000-2004
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  • 1
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    QPOs from Random X-ray Bursts around Rotating Black Holes (2009)
    In:  CASI
    Details
    Publication Date: 2018-06-06
    Description: We continue our earlier studies of quasi-periodic oscillations (QPOs) in the power spectra of accreting, rapidly-rotating black holes that originate from the geometric 'light echoes' of X-ray flares occurring within the black hole ergosphere. Our present work extends our previous treatment to three-dimensional photon emission and orbits to allow for arbitrary latitudes in the positions of the distant observers and the X-ray sources in place of the mainly equatorial positions and photon orbits of the earlier consideration. Following the trajectories of a large number of photons we calculate the response functions of a given geometry and use them to produce model light curves which we subsequently analyze to compute their power spectra and autocorrelation functions. In the case of an optically-thin environment, relevant to advection-dominated accretion flows, we consistently find QPOs at frequencies of order of approximately kHz for stellar-mass black hole candidates while order of approximately mHz for typical active galactic nuclei (approximately equal to 10(exp 7) solar mass) for a wide range of viewing angles (30 degrees to 80 degrees) from X-ray sources predominantly concentrated toward the equator within the ergosphere. As in out previous treatment, here too, the QPO signal is produced by the frame-dragging of the photons by the rapidly-rotating black hole, which results in photon 'bunches' separated by constant time-lags, the result of multiple photon orbits around the hole. Our model predicts for various source/observer configurations the robust presence of a new class of QPOs, which is inevitably generic to curved spacetime structure in rotating black hole systems.
    Keywords: Astrophysics
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    Smaller but Fully Functional Backshell for Cable Connector (2009)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: An improved design for the backshell of a connector for a shielded, multiplewire cable reduces the size of the backshell, relative to traditional designs of backshells of otherwise identical cable connectors. Notwithstanding the reduction in size, the design provides all the functionality typically demanded of such a backshell, including (1) termination of the cable shield (that is, grounding of the shield to the backshell), (2) strain relief for the cable, and (3) protection against electromagnetic interference (EMI).
    Keywords: Electronics and Electrical Engineering
    Type: MSC-23670-1 , NASA Tech Briefs, February 2009; 12-13
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    Mate replacement imposes a fitness cost on a socially monogamous seabird (2009)
    In:  [Talk] In: 46. Animal Behavior Society Conference, 22.-26.06.2009, Pirenopolis, Brazil .
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    Publication Date: 2013-12-04
    Type: Conference or Workshop Item , NonPeerReviewed
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    PAPER (OCEANREP)
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