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Title: Spectral broadening of radiation from relativistic collapsing objects

Abstract

We discuss light curves and the spectral broadening of the radiation emitted during a finite interval of time from the surface of a spherically symmetric collapsing object. We study a simplified model of monochromatic radiations. We discuss how one can obtain information about the physical parameters of the collapsing body, such as its mass and radius, from the light curves and spectral broadenin0008.

Authors:
 [1];  [2];  [1];  [3]
  1. Theoretical Physics Institute, Department of Physics, University of Alberta Edmonton, AB, T6G 2J1 (Canada)
  2. Department of Physics and BK21 Division of Advanced Research and Education in Physics, Hanyang University, Seoul 133-791 (Korea, Republic of)
  3. (Korea, Republic of)
Publication Date:
OSTI Identifier:
21020444
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. D, Particles Fields; Journal Volume: 75; Journal Issue: 8; Other Information: DOI: 10.1103/PhysRevD.75.087501; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; COSMOLOGY; EMISSION; GRAVITATIONAL COLLAPSE; LINE BROADENING; MASS; MONOCHROMATIC RADIATION; RELATIVISTIC RANGE; SURFACES

Citation Formats

Frolov, Valeri P., Kim, Kyungmin, Lee, Hyun Kyu, and Department of Physics and BK21 Division of Advanced Research and Education in Physics, Hanyang University, Seoul 133-791. Spectral broadening of radiation from relativistic collapsing objects. United States: N. p., 2007. Web. doi:10.1103/PHYSREVD.75.087501.
Frolov, Valeri P., Kim, Kyungmin, Lee, Hyun Kyu, & Department of Physics and BK21 Division of Advanced Research and Education in Physics, Hanyang University, Seoul 133-791. Spectral broadening of radiation from relativistic collapsing objects. United States. doi:10.1103/PHYSREVD.75.087501.
Frolov, Valeri P., Kim, Kyungmin, Lee, Hyun Kyu, and Department of Physics and BK21 Division of Advanced Research and Education in Physics, Hanyang University, Seoul 133-791. Sun . "Spectral broadening of radiation from relativistic collapsing objects". United States. doi:10.1103/PHYSREVD.75.087501.
@article{osti_21020444,
title = {Spectral broadening of radiation from relativistic collapsing objects},
author = {Frolov, Valeri P. and Kim, Kyungmin and Lee, Hyun Kyu and Department of Physics and BK21 Division of Advanced Research and Education in Physics, Hanyang University, Seoul 133-791},
abstractNote = {We discuss light curves and the spectral broadening of the radiation emitted during a finite interval of time from the surface of a spherically symmetric collapsing object. We study a simplified model of monochromatic radiations. We discuss how one can obtain information about the physical parameters of the collapsing body, such as its mass and radius, from the light curves and spectral broadenin0008.},
doi = {10.1103/PHYSREVD.75.087501},
journal = {Physical Review. D, Particles Fields},
number = 8,
volume = 75,
place = {United States},
year = {Sun Apr 15 00:00:00 EDT 2007},
month = {Sun Apr 15 00:00:00 EDT 2007}
}
  • In this work, we discuss observable characteristics of the radiation emitted from a surface of a collapsing object. We study a simplified model in which a radiation of massless particles has a sharp in time profile, and it happens at the surface at the same moment of comoving time. Since the radiating surface has finite size the observed radiation will occur during some finite time. Its redshift and bending angle are affected by the strong gravitational field. We obtain a simple expression for the observed flux of the radiation as a function of time. To find an explicit expression formore » the flux we develop an analytical approximation for the bending angle and time delay for null rays emitted by a collapsing surface. In the case of the bending angle this approximation is an improved version of the earlier proposed Beloborodov-Leahy-approximation. For rays emitted at R>2R{sub g} the accuracy of the proposed improved approximations for the bending angle and time delay is of order (or less) than 2%-3%. By using this approximation we obtain an approximate analytical expression for the observed flux and study its properties.« less
  • Wave equations are derived in terms of gauge-invariant amplitudes for odd-parity electromagnetic and gravitational perturbations of Oppenheimer-Snyder collapse. Numerical studies of the wave equations are presented, and it is shown that for the late stages of collapse (i) the radiation generated is insensitive to the dynamics of the stellar interiors, (ii) the radiation spectrum is dominated by radiation of quasi-normal frequencies, and (iii) l-pole fields fall off at very late times t in accordance with the predicted t/sup( -2l/+2) law.
  • Even-parity electromagnetic and gravitational linear perturbations of Oppenheimer-Snyder collapse are studied. The even-parity electromagnetic problem is shown to be identical to the analogous odd-parity electromagnetic problem. For the gravitational case, the mathematical appearance of the even-parity problem is markedly different from that for odd-parity. Numerical results are presented, however, which show that exterior radiation fields develop quite similarly in the tow problems and that previous conclusions (dominance of quasi-normal ringing, power-law tails late times) for odd-parity radiation apply equally well to the even-parity case.
  • We use the perturbation results of Cunningham, Moncrief, and Price to estimate the recoil velocities of newly formed black holes due to gravitational radiation reaction. We consider primarily the mixing of odd-parity quadrupole and octopole waves and obtain recoil velocities on the order of 25 km s/sup -1/ for the slightly nonspherical models of collapse considered by Cunningham, Moncrief, and Price. We discuss qualitatively how larger velocities might be attained in more highly nonspherical collapse and briefly compare our results with the quasi-Newtonian estimages of Bekenstein.
  • We study the gravitational waves generated during the collapse of a slowly rotating, pressureless, constant density star. To first order in the rotation rate the perturbation is an odd-parity dipole and generates no gravitational waves. The first order perturbation, however, drives a quadrupole deformation which is second order in the rotation rate and which produces the radiation. Using a gauge invariant description, we derive the equations governing this second order perturbation. These equations are then applied to the case of the collapse of a slowly and uniformly rotating constant-density star following the sudden turnoff of pressure. Numerical results are givenmore » for the gravitational waveforms and energies generated.« less