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Maurice H. P. M. van Putten

Publications and source records attributed to Maurice H. P. M. van Putten.

At least 91 records · Page 5Linked to original sources

Observational evidence for a correlation between peak-luminosities and beaming in GRBs

We calculate the unseen-but-true GRB-event rate from a current flux-limited sample of 33 GRBs with individually measured redshifts. We consider a GRB-event rate which is proportional to the star-formation rate, in view of the GRB-SNe association in SN1998bw and GRB030329. By fitting a log-normal distribution of GRB peak-luminosities, we find a ratio of about 450 for the true-to-observed GRB-event rates. This provides an independent derivation of the GRB-beaming factor of about 500 obtained by Frail et al. (2001) from sources with standard GRB-energies. We discuss applications to GRB980425.

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Gravitational waves from gamma-ray bursts

We present a mechanism for long bursts of gravitational radiation from Kerr black holes surrounded by a torus. These systems are believed to form in core-collapse of massive stars in association with gamma-ray bursts. The torus catalyzes black hole-spin energy mostly into gravitational radiation, with a minor output in winds, thermal and neutrino emissions. Torus winds impact the remnant envelope of the progenitor star from within, which may account for X-ray emission lines and leaves a supernova remnant. The frequency in gravitational radiation satisfies f_{gw}=470Hz (E_{SNR}/4\times 10^{51})^{1/2}(0.1/β)^{1/2}(7M_\odot/M_H)^{3/2}, where E_{SNR} is the kinetic energy in the SNR, M_H is the black hole mass and β\simeq0.1 the initial ejection velocity, as detected in GRB 011211. Ultimately, this leaves a black hole binary surrounded by a SNR, which is conceivably illustrated by RX J050736-6847.8.

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Theory and astrophysical consequences of a magnetized torus around a rapidly rotating black hole

(Abbrev.) We analyze the topology, lifetime, and emissions of a torus around a black hole formed in hypernovae and black hole-neutron star coalescence. The torus is ab initio uniformly magnetized, represented by two counter oriented current-rings, and develops a state of suspended accretion against a "magnetic wall" around the black hole. Magnetic stability of the torus gives rise to a new fundamental limit EB/Ek<0.1 for the ratio of poloidal magnetic field energy-to-kinetic energy. The lifetime of rapid spin of the black hole is effectively defined by the timescale of dissipation of black hole-spin energy in the horizon, and satisfies T= 40s (MH/7MSun)(R/6MH)^4(0.03MH/MT) for a black hole of mass MH surrounded by a torus of mass MT and radius R. The torus converts a major fraction Egw/Erot=0.1 into gravitational radiation through a finite number of multipole mass-moments, and a smaller fraction into MeV neutrinos and baryon-rich winds. At a source distance of 100Mpc, these emissions over N=2e4 periods give rise to a characteristic strain amplitude \sqrt{N}hchar=6e-21. We argue that torus winds create an open magnetic flux-tube on the black hole, which carries a minor and standard fraction Ej/Erot=1e-3 in baryon-poor outflows to infinity. We identify this baryon poor output of tens of seconds with GRBs with contemporaneous and strongly correlated emissions in gravitational radiation, conceivably at multiple frequencies. Ultimately, this leaves a black hole binary surrounded by a supernova remnant.

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Gravitational wave frequencies and energies in hypernovae

A torus develops a state of suspended accretion against a magnetic wall around a rapidly rotating black hole formed in core-collapse hypernovae. It hereby emits about 10% of the black hole spin-energy in gravitational radiation from a finite number of multipole mass moments. We quantify the relation between the frequency of quadrupole gravitational radiation and the energy output $E_w$ in torus winds by $f_{gw}\simeq 470{Hz}(E_w/4\times 10^{52}{erg})^{1/2}(7M_\odot/M)^{3/2}$, where $M$ denotes the mass of the black hole. We propose that $E_w$ irradiates the remnant stellar envelope from within. We identify $E_w$ with energies $\sim 10^{52}$ erg inferred from X-ray observations on matter injecta; and the poloidal curvature in the magnetic wall with the horizon opening angle in baryon poor outflows that power true GRB energies of $E_γ\simeq 3\times 10^{51}$ erg.

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Uniqueness in MHD in divergence form: right nullvectors and well-posedness

Magnetohydrodynamics in divergence form describes a hyperbolic system of covariant and constraint-free equations. It comprises a linear combination of an algebraic constraint and Faraday's equations. Here, we study the problem of well-posedness, and identify a preferred linear combination in this divergence formulation. The limit of weak magnetic fields shows the slow magnetosonic and Alfven waves to bifurcate from the contact discontinuity (entropy waves), while the fast magnetosonic wave is a regular perturbation of the hydrodynamical sound speed. These results are further reported as a starting point for characteristic based shock capturing schemes for simulations with ultra-relativistic shocks in magnetized relativistic fluids.

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Proposed gravitational wave background from black hole-torus systems

Cosmological gamma-ray bursts may be powered by rotating black holes with contemporaneous emission of gravitational radiation from a surrounding torus. We calculate the resulting stochastic background radiation assuming strong cosmological evolution and a uniform black hole mass distribution of M= (4--14)M_odot. The predicted spectral flux density corresponds to a peak spectral closure density of (1--2) times 10^{-7}, and has comparable contributions at 450 Hz times kappa and over 300--450 Hz times kappa from nearby and distant sources, respectively, where kappa refers to an uncertainty factor of order unity in the radius of the torus. For two optimized advanced LIGO-type detectors the proposed gravitational wave background could be detectable within a year of integration.

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LIGO/VIRGO searches for gravitational radiation in hypernovae

A torus around a stellar mass Kerr black hole can emit about 10% of the spin-energy of the black hole in gravitational radiation, potentially associated with a gamma-ray burst. Wide tori may develop buckling modes by the Papaloizou-Pringle instability and gravitational radiation-reaction forces in the Burke-Thorne approximation. Gravitational wave experiments may discover these emissions in a fraction of nearby supernovae. This provides a test for Kerr black holes, and for GRB inner engines by comparison with the de-redshifted durations of long GRBs.

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Vistas in numerical relativity

Upcoming gravitational wave-experiments promise a window for discovering new physics in astronomy. Detection sensitivity of the broadband laser interferometric detectors LIGO/VIRGO may be enhanced by matched filtering with accurate wave-form templates. Where analytic methods break down, we have to resort to numerical relativity, often in Hamiltonian or various hyperbolic formulations. Well-posed numerical relativity requires consistency with the elliptic constraints of energy and momentum conservation. We explore this using a choice of gauge in the future and a dynamical gauge in the past. Applied to a polarized Gowdy wave, this enables solving {\em all} ten vacuum Einstein equations. Evolution of the Schwarzschild metric in 3+1 and, more generally, sufficient conditions for well-posed numerical relativity continue to be open challenges.

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Past and future gauge in numerical relativity

Numerical relativity describes a discrete initial value problem for general relativity. A choice of gauge involves slicing space-time into space-like hypersurfaces. This introduces past and future gauge relative to the hypersurface of present time. Here, we propose solving the discretized Einstein equations with a choice of gauge in the future and a dynamical gauge in the past. The method is illustrated on a polarized Gowdy wave.

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Gamma-ray bursts: the tip of the iceberg?

The spin-energy $E_{rot}$ of a Kerr black hole surrounded by a torus may power emissions in multiple windows. The recently determined true GRB-energy of $3-5\times 10^{50}$ erg indicates a minor fraction $E_j/E_{rot}\simeq 0.1%$ in baryon poor ouput, here considered as jets along open magnetic flux-tubes from the horizon to infinity. A major fraction $E_{gw}/E_{rot}\simeq 5%$ is expected in gravitational radiation from the torus. A LIGO/VIRGO detection of $α=2π\int fdE_{gw}$ in excess of the neutron star limit $α^*\simeq 0.005$ promises a calorimetric test for Kerr black holes. We expect a sample of LIGO/VIRGO detections to obey the distribution of redshift corrected GRB-durations.

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Baryon-poor outflows from rotating black holes

Cosmological gamma-ray bursts are probably powered by systems harboring a rotating black hole. We show that frame-dragging creates baryon-poor outflows in a differentially rotating gap along an open magnetic flux-tube with dissipation $P=Ω_T(Ω_H-2Ω_T)A_ϕ^2$, where $2πA_ϕ$ denotes the flux in the open tube, for angular velocities $Ω_H$ and $Ω_T$ of the black hole and the torus, respectively. The output in photon-pair outflow will be reprocessed in an intervening hypernova progenitor wind or the ISM.

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A calorimetric test for Kerr black holes in gamma-ray bursts

Cosmological gamma-ray bursts are potentially associated with systems harboring a black rotating black hole. Calorimetry on yet "unseen" emissions in gravitational waves from a surrounding torus may provide a measure for its rotational energy. We introduce a compactness parameter $α=2π\int fdE$ for the fluence $E$ and frequency $f$ in gravitational waves. For black hole-torus systems, $α\simeq 2πEf\simeq 0.005-0.05$ may exceed the upper bound $α^*\simeq 0.005$ for rapidly rotating neutron stars. A duration in gravitational radiation consistent with the redshift corrected durations of the BATSE catalogue defines an association with long GRBs. This promises a new test for Kerr black holes as objects in Nature.

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Gamma-ray bursts and gravitational radiation from black hole-torus systems

Cosmological gamma-ray bursts (GRBs) are probably powered by systems harboring a rotating black hole. These may result from hypernovae or black hole-neutron star coalescence. We identify short/long bursts with hyper- and suspended-accretion states around slowly/rapidly spinning black holes. Baryon poor jets, as input to the observed GRB/afterglow emissions, may result from dissipation in a gap along an open flux-tube on the axis of rotation of the black hole. The torus is expected to radiate a major fraction of the black hole luminosity into gravitational waves, which suggests that long GRBs may be the most powerful LIGO/VIRGO burst sources in the Universe. (Abbreviated)

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Gravitational radiation from a torus around a black hole

Long gamma-ray bursts (GRBs) from rapidly spinning black hole-torus systems may represent hypernovae or black hole-neutron star coalescence. We show that the torus may radiate gravitational radiation powered by the spin-energy of the black hole in the presence of non-axisymmetries. The coupling to the spin-energy of the black hole is due to equivalence in poloidal topology to pulsar magnetospheres. Results calculated in the suspended accretion state indicate that GRBs are potentially the most powerful LIGO/VIRGO burst-sources in the Universe, with an expected duration of 10-15s on a horizontal branch of 1-2kHz in the $\dot{f}(f)-$diagram.

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Calorimetry of gamma-ray bursts: echos in gravitational waves

Black holes surrounded by a disk or torus may drive the enigmatic cosmological gamma-ray bursts (GRBs). Equivalence in poloidal topology to pulsar magnetospheres shows a high incidence of the black hole-luminosity $L_H$ into the surrounding magnetized matter. We argue that this emission is re-radiated into gravitational waves at $L_{GW}\simeq L_H/3$ in frequencies of order 1kHz, winds and, potentially, MeV neutrinos. The total energy budget and input to the GRB from baryon poor jets are expected to be standard in this scenario, consistent with recent analysis of afterglow data. Collimation of these outflows by baryon rich disk or torus winds may account for the observed spread in opening angles up to about $35^o$. This model may be tested by future LIGO/VIRGO observations.

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Hyper- and suspended-accretion states of rotating black holes and the durations of gamma-ray bursts

We analyze the temporal evolution of accretion onto rotating black holes subject to large-scale magnetic torques. Wind torques alone drive a disk towards collapse in a finite time $\sim t_{ff} E_k/E_B$, where $t_{ff}$ is the initial free-fall time and $E_k/E_B$ is the ratio of kinetic-to-poloidal magnetic energy. Additional spin-up torques from a rapidly rotating black hole can arrest the disk's inflow. We associate short/long gamma-ray bursts with hyperaccretion/suspended-accretion onto slowly/rapidly spinning black holes. This model predicts afterglow emission from short bursts, and may be tested by HETE-II.

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Electric Charge and Magnetic Flux on Rotating Black Holes in a Force-Free Magnetosphere

The electric charge on rotating black holes is calculated to be ~ BJ in the force-free configuration of Ghosh (2000), with a horizon flux of ~ BM^2. This charge is gravitationally weak for B ~ 10^{15} G, so that the Kerr metric applies. Being similar to the electric charge of a magnetar, both electric charge and magnetic flux should be, in sign and order of magnitude, continuous during stellar collapse into a black hole. Extraction of the rotational energy from newly formed black holes may proceed by interaction with the magnetic field. Keywords:black hole physics --magnetic fields

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Gravitational radiation from long gamma-ray bursts

Long gamma-ray bursts (GRBs) are probably powered by high-angular momentum black hole-torus systems in suspended accretion. The torus will radiate gravitational waves as non-axisymmetric instabilities develop. The luminosity in gravitational-wave emissions is expected to compare favorably with the observed isotropic equivalent luminosity in GRB-afterglow emissions. This predicts that long GRBs are potentially the most powerful LIGO/VIRGO burst-sources in the Universe. Their frequency-dynamics is characterized by a horizontal branch in the $\dot{f}(f)-$diagram.

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