Transcript CENTRA report

Gravitational waves
astronomy for the new millennium
Vitor Cardoso
(CENTRA/IST & U. Mississippi)
Collaborators: Berti, Bruegmann, Gonzalez, Pani, Pretorius, Sperhake, Will, Witek, etc
IBERICOS 2009, Madrid, 16 April
(Image: MPI for Gravitational Physics/W.Benger-Z)
Plan
GWs in GR
Coalescence of black hole binaries in GR
Other theories
What are GWs?
“+” polarization:
“x” polarization:
Wave equation: c!
Observable:
Gws are tidal forces!
Do they exist?
slow down of a binary pulsar
Do they exist?
slow down of a black hole in quasar OJ 287:
strong-field tests
Valtonen et al, Nature452, 851-853 (17 April 2008)
Detection
Typical signal for coalescing binaries
LIGO-G080249-00-Z
Typical stretch of data
LIGO-G080249-00-Z
Typical needle in a haystack problem
(but with a smaller needle)
LIGO-G080249-00-Z
Typical needle in a haystack problem
LIGO-G080249-00-Z
Matched filtering
LIGO-G080249-00-Z
Matched filtering
LIGO-G080249-00-Z
Matched filtering
LIGO-G080249-00-Z
Matched filtering
LIGO-G080249-00-Z
Matched filtering
LIGO-G080249-00-Z
Matched filtering
LIGO-G080249-00-Z
The merger problem: we need NR
Lack of knowledge
Wrong filter
Mismatch
Decreased SNR
3% Mismatch: 10% lost events!
LIGO-G080249-00-Z
BH Binary
Coalescence
Rates for LISA (similar variations for LIGO)
BH coalescence
Courtesy Marcus Thierfelder and Bernd Bruegmann
Typical signal for BH binaries
Inspiral
Merger
Ringdown
(Berti, VC, Sperhake, Gonzalez, Brugmann, Hannam & Husa,PRD76:064034,2007)
Inspiral
Luminosity distance
Angular resolution
(sterad)
reduced mass
Chirp mass
(Faye et al ’06, Kidder ‘08)
Inspiral
Inspiral PN waveforms
•
High-precision tests of GR
Mass, distance, angular location to fractions of a percent
Luminosity distance
Luminosity distance
Angular resolution
(sterad)
Angular resolution
reduced mass
(sterad)
reduced mass
Chirp mass
2x106M (solid) and 2x107M (dashed)(Berti, Buonanno & Will, PRD71:084025,2005)
Inspiral
Inspiral PN waveforms
•
High-precision tests of GR
Mass, distance, angular location to fractions of a percent
Luminosity distance
•
Propagation speed, Polarization states
•
Masslessness of graviton: speedAngular
depends
on wavelength,
resolution
(sterad)
therefore phasing changes during inspiral (Arun and Will, ‘09)
reduced mass
•
EOS for dark energy: identify host galaxy and measure redshift
from EM. Distance and redshift gives EOS (Arun et al, ‘08)
BH ringdown: characteristic modes
r  4    Almn exp(ilmnt )Slmn ( ,  )
lmn
(Leaver ’85; Berti, VC & Starinets, ‘09)
f = 12 Msun/M kHz = 0.012 (106Msun)/M Hz
t =55x10-6M/Msun s= 55
M/(106Msun) s
LIGO-G080249-00-Z
“No-hair” tests

One mode detection:
 Suppose
we know which mode we are detecting
(eg. l=m=2); then
f(M,j), t(M,j)
 Measure
M(f,t), j(f,t)
of black hole’s mass and angular momentum
(Echeverria ’89, Finn ’92)

Multi-mode detection:
mode yields (M,j)
 In GR, Kerr modes depend only on M and j:
second mode yields test that we are observing a Kerr black
hole, if we can resolve the modes:
 First
| f1  f 2 | max( f1 , f2 )
LIGO-G080249-00-Z
(Dreyer et al. ’05;
Berti, VC & Will ’06)
Ringdown: LISA
j=0,0.8,0.98
Berti, VC & Will, PRD71:084025,2005)
On-going:
Credible consistent theories of gravity
•
Chern-Simons (Sopuerta & Yunes ‘09, Alexander & Yunes ‘08),
Dilaton-Gauss-Bonnet (VC & Pani, ‘09), etc.
Maybe a general framework? (Pretorius & Yunes, ‘09)
•
Numerical Relativity in different theories (see Helvi’s talk)
Work in progress
•
Good news for gravitational-wave detection
•
Bad news for quest for “corrected” theory of gravity
Conclusions
Exciting times for gravitational wave astronomy:
 Advances in theory and numerical relativity
 Earth-based detectors have reached design sensitivity
 Probe central engine for GRBs
 Demographics of very compact objects (mass & spin to better than 1%!)
 Does GR describe strong field regime?
?
Thank you
Typical BH binary
Order of magnitude estimate
For a coalescing compact object into a black hole:
Distance Earth-Sun (1.5 x 107 km)….
…stretches by a fraction of an atom!
BH coalescence
The merger problem
LIGO-G080249-00-Z
Interferometry
Hanford, WA
Livingston, LA
BH ringdown: combing 3 hairs
LIGO-G080249-00-Z