Synergy with Gravitational Waves

Transcription

1 Synergy with Gravitational Waves Alexandre Le Tiec and Jérôme Novak Laboratoire Univers et Théories Observatoire de Paris / CNRS LIGO, Virgo, ( elisa, ET,... (

2 What is a gravitational wave? A gravitational wave is a perturbation in the curvature of spacetime that propagates at the vacuum speed of light gravitational wave c background curvature h ab g ab = ḡ ab + h ab g ab Key prediction of Einstein s theory of General Relativity

3 Complementarity with observations of EM radiation Gravitational waves Bulk motion of mass-energy Coherent superposition Wavelength size source Quadrupolar nature Weak interaction w/ matter Propagate almost freely Detection of ampl. ( 1/D) Electromagnetic waves Acceleration of many charges Incoherent superposition Wavelength size source Dipolar nature Strong interaction w/ matter Scattered, reflected, refracted Detection of power ( 1/D 2 ) Orthogonal sources of information about the Universe

4 Indirect evidence of gravitational waves Binary pulsar PSR B [Hulse & Taylor, ApJ (1975)] Double pulsar PSR J [Burgay et al., Nature (2003)] Orbital decay due to GW emission confirmed at the 0.1% level

5 The gravitational wave spectrum

6 Science with gravitational wave observations Fundamental physics Precision tests of GR in the non-linear regime Existence of black holes cosmic censorship Dark energy equation of state w = p/ρ Astrophysics Formation and evolution of compact binaries Origin and mechanism of γ-ray bursts Internal structure of neutron stars Cosmology Cosmography and independent measure of H 0 Origin and growth of supermassive black holes Phase transitions in the early Universe

7 Ground-based laser interferometric detectors Virgo (Cascina, Italy) LIGO (Livingston, USA) 6 science runs and 80 publications over No direct detection but stringent upper limits, e.g. Ellipticity of Crab pulsar < 10 4 [Abbott et al., ApJ (2008)] Energy density of GW stochastic background < around 100 Hz [Abbott et al., Nature (2009)]

8 A worldwide network of GW observatories Ongoing upgrade to Advanced LIGO/Virgo, KAGRA in Japan 2 nd generation detectors: sensitivity 10 event rates 10 3 Beginning of gravitational wave astronomy

9 elisa: a gravitational wave antenna in space LISA Pathfinder elisa/ngo LISA Pathfinder scheduled for launch in 2015 Gravitational Universe science theme was recommended to ESA s SPC for the L3 mission with a nominal launch in 2034 If LISA Pathfinder is successful then elisa should fly!

10 Gamma-ray bursts and gravitational waves Standard model for the central engine of GRBs: Long GRBs: collapse of massive rotating star (Hypernova) Short GRBs : binary neutron star coalescence both scenarios end forming a black hole with a disk of nuclear matter (non-negligible mass) both events produce high amount of gravitational waves.

11 Short GRBs Test of the BNS merger model Numerical studies by Kiuchi et al. (2010) : not all mergers can result in a sufficiently massive disk to produce a GRB strategy for the exploration of the merger hypothesis, analyzing gravitational waves Information about the progenitor Gravitational wave polarization inclination angle between the binary and the observer (Kobayashi & Mészáros 2003) Observational constraints on the host galaxy Use of LIGO data from S5 run searching a counterpart for GRB : sky position coincident with M31 exclusion of BNS merger, closer than 3.5 Mpc (includes Andromeda) Abbott et al. (2008) (arxiv: )

12 Collapse of massive stars Standard model: collapsar (Woosley 1993) Delayed collapse to a black hole from a massive (fast) rotating star. Energy extracted by thermal deposition (ν ν annihilation) or hydromagnetic. Event closer to spherical symmetry less gravitational waves: perturbed torus (Montero et al. 2007), black hole ringing, neutrino anisotropic emission or magneto-rotational processes (Scheidegger et al. 2010) little chances for extra-galactic sources but possibly valuable information concerning central engine.

13 Summary and prospects Beginning of gravitational wave astronomy Observations of GWs will complement those of EM waves Some GRB-GW science targets: Connection of short GRBs with merging compact binaries Are the binaries NS-NS or BH-NS? How much of each? Measurements of luminosity distance for short GRBs Determination of the γ-ray beaming angles Can we see GWs from progenitors of long GRBs? LIGO, Virgo, ( elisa, ET,... (