The Experts below are selected from a list of 6438 Experts worldwide ranked by ideXlab platform
Abraham Loeb - One of the best experts on this subject based on the ideXlab platform.
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prompt tidal disruption of stars as an Electromagnetic Signature of supermassive black hole coalescence
Monthly Notices of the Royal Astronomical Society, 2011Co-Authors: Nicholas C Stone, Abraham LoebAbstract:In the last decade, a series of breakthroughs in numerical relativity made it possible to simulate black hole binary coalescence on the computer, in fully dynamical spacetime (Pretorius 2005; Baker et al. 2006; Campanelli et al. 2006). The most important astrophysical result of these new techniques has been a self-consistent calculation of gravitational wave (GW) kicks: the recoil imparted via momentum conservation to a newly merged black hole. The final stages of black hole inspiral and merger are accompanied by anisotropic GW emission, which has been numerically demonstrated to produce typical recoil kicks \(\sim\!\!10^{2-3}~{\rm km~s}^{-1}\). The magnitude of the kick depends most sensitively on the initial binary mass ratio and on the spin vectors of the black holes.
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prompt tidal disruption of stars as an Electromagnetic Signature of supermassive black hole coalescence
arXiv: Cosmology and Nongalactic Astrophysics, 2010Co-Authors: Nicholas C Stone, Abraham LoebAbstract:A precise Electromagnetic measurement of the sky coordinates and redshift of a coalescing black hole binary holds the key for using its gravitational wave (GW) signal to constrain cosmological parameters and to test general relativity. Here we show that the merger of ~10^{6-7}M_sun black holes is generically followed over a period of years by multiple Electromagnetic flares from tidally disrupted stars. The sudden recoil imparted to the merged black hole by GW emission promptly fills its loss cone and results in a tidal disruption rate of stars as high as ~0.1 per year. The prompt disruption of a star within a single galaxy over a short period provides a unique Electromagnetic flag of a recent black hole coalescence event, and sequential disruptions could be used on their own to calibrate the expected rate of GW sources for pulsar timing arrays or the proposed Laser Interferometer Space Antenna (LISA).
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repeating tidal disruption of stars as a prompt Electromagnetic Signature of supermassive black hole coalescence
2010Co-Authors: Nicholas C Stone, Abraham LoebAbstract:A precise Electromagnetic measurement of the sky coordinates and redshift of a coalescing black hole binary holds the key for using its gravitational wave (GW) signal to constrain cosmological parameters and to test general relativity. Here we show that the merger of ~10^{6-7}M_sun black holes is generically followed over a period of years by multiple Electromagnetic flares from tidally disrupted stars. The sudden recoil imparted to the merged black hole by GW emission promptly fills its loss cone and results in a tidal disruption rate of stars as high as ~0.1 per year. The prompt disruption of a star within a single galaxy over a short period provides a unique Electromagnetic flag of a recent black hole coalescence event, and sequential disruptions could be used on their own to calibrate the expected rate of GW sources for pulsar timing arrays or the proposed Laser Interferometer Space Antenna (LISA).
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Electromagnetic Signature of supermassive black hole binaries that enter their gravitational wave induced inspiral
Physical Review D, 2010Co-Authors: Abraham LoebAbstract:Mergers of gas-rich galaxies lead to black hole binaries that coalesce as a result of dynamical friction on the ambient gas. Once the binary tightens to $\ensuremath{\lesssim}{10}^{3}$ Schwarzschild radii, its merger is driven by the emission of gravitational waves (GWs). We show that this transition occurs generically at orbital periods of $\ensuremath{\sim}1\char21{}10\text{ }\text{ }\mathrm{years}$ and an orbital velocity $v$ of a few thousand $\mathrm{km}\text{ }{\mathrm{s}}^{\ensuremath{-}1}$, with a very weak dependence on the supply rate of gas ($v\ensuremath{\propto}{\stackrel{\ifmmode \dot{}\else \textperiodcentered \fi{}}{M}}^{1/8}$). Therefore, as binaries enter their GW-dominated inspiral, they inevitably induce large periodic shifts in the broad emission lines of any associated quasar(s). The probability of finding a binary in tighter configurations scales as ${v}^{\ensuremath{-}8}$ owing to their much shorter lifetimes. Narrow-band monitoring of the broad emission lines of quasars on time scales of months to decades can set a lower limit on the expected rate of GW sources for the Laser Interferometer Space Antenna.
Rosanne Di Stefano - One of the best experts on this subject based on the ideXlab platform.
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detecting gravitational self lensing from stellar mass binaries composed of black holes or neutron stars
Monthly Notices of the Royal Astronomical Society, 2020Co-Authors: Daniel J Dorazio, Rosanne Di StefanoAbstract:We explore a unique Electromagnetic Signature of stellar-mass compact-object binaries long before they are detectable in gravitational waves. We show that gravitational lensing of light emitting components of a compact-object binary, by the other binary component, could be detectable in the nearby universe. This periodic lensing Signature could be detected from present and future X-ray observations, identifying the progenitors of binaries that merge in the LIGO band, and also unveiling populations that do not merge, thus providing a tracer of the compact-object binary population in an enigmatic portion of its life. We argue that periodically repeating lensing flares could be observed for ~100 ksec orbital-period binaries with the future Lynx X-ray mission, possibly concurrent with gravitational wave emission in the LISA band. Binaries with longer orbital periods could be more common and be detectable as single lensing flares, though with reliance on a model for the flare that can be tested by observations of succeeding flares. Non-detection of such events, even with existing X-ray observations, will help to constrain the population of EM bright compact-object binaries.
Abdesselam Bouzerdoum - One of the best experts on this subject based on the ideXlab platform.
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a subspace projection approach for wall clutter mitigation in through the wall radar imaging
IEEE Transactions on Geoscience and Remote Sensing, 2015Co-Authors: Fok Hing Chi Tivive, Abdesselam BouzerdoumAbstract:One of the main challenges in through-the-wall radar imaging (TWRI) is the strong exterior wall returns, which tend to obscure indoor stationary targets, rendering target detection and classification difficult, if not impossible. In this paper, an effective wall clutter mitigation approach is proposed for TWRI that does not require knowledge of the background scene nor does it rely on accurate modeling and estimation of wall parameters. The proposed approach is based on the relative strength of the exterior wall returns compared to behind-wall targets. It applies singular value decomposition to the data matrix constructed from the space-frequency measurements to identify the wall subspace. Orthogonal subspace projection is performed to remove the wall Electromagnetic Signature from the radar signals. Furthermore, this paper provides an analysis of the wall and target subspace characteristics, demonstrating that both wall and target subspaces can be multidimensional. While the wall subspace depends on the wall type and building material, the target subspace depends on the location of the target, the number of targets in the scene, and the size of the target. Experimental results using simulated and real data demonstrate the effectiveness of the subspace projection method in mitigating wall clutter while preserving the target image. It is shown that the performance of the proposed approach, in terms of the improvement factor of the target-to-clutter ratio, is better than existing approaches and is comparable to that of background subtraction, which requires knowledge of a reference background scene.
Nicholas C Stone - One of the best experts on this subject based on the ideXlab platform.
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prompt tidal disruption of stars as an Electromagnetic Signature of supermassive black hole coalescence
Monthly Notices of the Royal Astronomical Society, 2011Co-Authors: Nicholas C Stone, Abraham LoebAbstract:In the last decade, a series of breakthroughs in numerical relativity made it possible to simulate black hole binary coalescence on the computer, in fully dynamical spacetime (Pretorius 2005; Baker et al. 2006; Campanelli et al. 2006). The most important astrophysical result of these new techniques has been a self-consistent calculation of gravitational wave (GW) kicks: the recoil imparted via momentum conservation to a newly merged black hole. The final stages of black hole inspiral and merger are accompanied by anisotropic GW emission, which has been numerically demonstrated to produce typical recoil kicks \(\sim\!\!10^{2-3}~{\rm km~s}^{-1}\). The magnitude of the kick depends most sensitively on the initial binary mass ratio and on the spin vectors of the black holes.
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prompt tidal disruption of stars as an Electromagnetic Signature of supermassive black hole coalescence
arXiv: Cosmology and Nongalactic Astrophysics, 2010Co-Authors: Nicholas C Stone, Abraham LoebAbstract:A precise Electromagnetic measurement of the sky coordinates and redshift of a coalescing black hole binary holds the key for using its gravitational wave (GW) signal to constrain cosmological parameters and to test general relativity. Here we show that the merger of ~10^{6-7}M_sun black holes is generically followed over a period of years by multiple Electromagnetic flares from tidally disrupted stars. The sudden recoil imparted to the merged black hole by GW emission promptly fills its loss cone and results in a tidal disruption rate of stars as high as ~0.1 per year. The prompt disruption of a star within a single galaxy over a short period provides a unique Electromagnetic flag of a recent black hole coalescence event, and sequential disruptions could be used on their own to calibrate the expected rate of GW sources for pulsar timing arrays or the proposed Laser Interferometer Space Antenna (LISA).
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repeating tidal disruption of stars as a prompt Electromagnetic Signature of supermassive black hole coalescence
2010Co-Authors: Nicholas C Stone, Abraham LoebAbstract:A precise Electromagnetic measurement of the sky coordinates and redshift of a coalescing black hole binary holds the key for using its gravitational wave (GW) signal to constrain cosmological parameters and to test general relativity. Here we show that the merger of ~10^{6-7}M_sun black holes is generically followed over a period of years by multiple Electromagnetic flares from tidally disrupted stars. The sudden recoil imparted to the merged black hole by GW emission promptly fills its loss cone and results in a tidal disruption rate of stars as high as ~0.1 per year. The prompt disruption of a star within a single galaxy over a short period provides a unique Electromagnetic flag of a recent black hole coalescence event, and sequential disruptions could be used on their own to calibrate the expected rate of GW sources for pulsar timing arrays or the proposed Laser Interferometer Space Antenna (LISA).
Eliot Quataert - One of the best experts on this subject based on the ideXlab platform.
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fossil gas and the Electromagnetic precursor of supermassive binary black hole mergers
Monthly Notices of the Royal Astronomical Society, 2010Co-Authors: Philip Chang, Linda E Strubbe, Kristen Menou, Eliot QuataertAbstract:Using a 1D height integrated model, we calculate the evolution of an unequal mass binary black hole with a coplanar gas disc that contains a gap due to the presence of the secondary black hole. Viscous evolution of the outer circumbinary disc initially hardens the binary, while the inner disc drains on to the primary (central) black hole. As long as the inner disc remains cool and thin at low M ext (rather than becoming hot and geometrically thick), the mass of the inner disc reaches an asymptotic mass typically ∼10 -3 -10 -4 M⊙. Once the semimajor axis shrinks below a critical value, angular momentum losses from gravitational waves dominate over viscous transport in hardening the binary. The inner disc then no longer responds viscously to the inspiraling black holes. Instead, tidal interactions with the secondary rapidly drive the inner disc into the primary. Tidal and viscous dissipation in the inner disc lead to a late time brightening in luminosity, L oc t -5/4 minus , where t minus is the time prior to the final merger. This late time brightening peaks ∼1 d prior to the final merger at ∼0.1L Edd . This behaviour is relatively robust because of self-regulation in the coupled viscous-gravitational evolution of such binary systems. It constitutes a unique Electromagnetic Signature of a binary supermassive black hole merger and may allow the host galaxy to be identified if used in conjunction with the Laser Interferometric Space Antenna localization.
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fossil gas and the Electromagnetic precursor of supermassive binary black hole mergers
arXiv: High Energy Astrophysical Phenomena, 2009Co-Authors: Philip Chang, Linda E Strubbe, Kristen Menou, Eliot QuataertAbstract:Using a one-dimensional height integrated model, we calculate the evolution of an unequal mass binary black hole with a coplanar gas disk that contains a gap due to the presence of the secondary black hole. Viscous evolution of the outer circumbinary disk initially hardens the binary, while the inner disk drains onto the primary (central) black hole. As long as the inner disk remains cool and thin at low $\dot{M}_{\rm ext}$ (rather than becoming hot and geometrically thick), the mass of the inner disk reaches an asymptotic mass typically $\sim 10^{-3}-10^{-4}\Msun$. Once the semimajor axis shrinks below a critical value, angular momentum losses from gravitational waves dominate over viscous transport in hardening the binary. The inner disk then no longer responds viscously to the inspiraling black holes. Instead, tidal interactions with the secondary rapidly drive the inner disk into the primary. Tidal and viscous dissipation in the inner disk lead to a late time brightening in luminosity $L\propto t_{\rm minus}^{5/4}$, where $t_{\rm minus}$ is the time prior to the final merger. This late time brightening peaks $\sim 1$ day prior to the final merger at $\sim 0.1 L_{\rm Edd}$. This behavior is relatively robust because of self regulation in the coupled viscous-gravitational evolution of such binary systems. It constitutes a unique Electromagnetic Signature of a binary supermassive black hole merger and may allow the host galaxy to be identified if used in conjunction with the Laser Interferometric Space Antenna (LISA) localization.