Grav ravitatio itational W al Wav aves es in in th the L e - - PowerPoint PPT Presentation

Calloni, E., Calloni, E., Capozziello,S., apozziello,S., De Rosa,R., De Laurentis, e Rosa,R., De Laurentis, M.,Di Fiore L.,Forte,L.,Garufi,F. M.,Di Fiore L.,Forte,L.,Garufi,F. L.Milano Department of Physical Sciences University of Federico II Naples & INFN Napoli

Grav ravitatio itational W al Wav aves es in in th the L e LIG IGO -

• VIR

IRGO era era

• r listening to the

symphony of the Universe

The emerging science of gravitational wave astronomy is optimistically named!

Astronomy depends ultimately on observations, yet the only output of gravitational wave detectors has so far been noise generated within the instruments. Actually we can be called noise hunters! There is good reason, based on experimental and theoretical progress, to believe that things are about to change. As an example of progress on the theoretical side there are simulations of neutron star mergers that reveal new details of the gravitational waves they are expected to emit IMR waveforms The effort to detect gravitational waves started humbly fifty years ago with Joe Weber’s bar detectors and great efforts were made mainly in Italy to develop such kind of detectors. They opened the way to the actual interferometric detectors: starting from a bandwidth of a maximum of 50 Hertz around 960 Hz(bar criogenic antennas) nowdays we realized antennas with useful bandwidth of thosandths of Hz, namely 10-10 kHz (Virgo) 40-10 kHz Ligo BUT No yet detection of GW signal notwithstanding the target sensitivity was reached either for VIRGO or for LIGO: let us see now what is the state of art

GW in rough pills GW in rough pills Indirect evidences of the GW existence Indirect evidences of the GW existence The Global Network of earth based detectors The Global Network of earth based detectors The GW sources zoo & Results up to now The GW sources zoo & Results up to now Multifrequency Observations and GWs Multifrequency Observations and GWs  understanding astrophysical processes understanding astrophysical processes  multi-messenger astronomy multi-messenger astronomy The space based detec.: LISA Pathfinder ,LISA The space based detec.: LISA Pathfinder ,LISA The Near Future.The new proposals The Near Future.The new proposals Conclusions Conclusions

Gravitational Waves in rough pills Gravitational Waves in rough pills

The GW Amplitude in TT system For a GW propagating along X3 we obtain the amplitude:

The polarizations + and x are exchanged with a π/4 rotation around x3 axis i.e. GW are spin 2 massless fields. In the limit of weak gravity, GW amplitude is proportional to the second time derivative of the source mass quadrupole moment:

Indirect evidences of the GW existence Indirect evidences of the GW existence

Good testbed for theories of gravitation! Now there are about 6 similar systems, and the “double pulsar” PSR J0737-3039 is already overtaking 1913 in precision. All agree with GR but could be interesting a test of f(R) theories?

Orbital period decreasing changes periastron passage time in agreement with GR J.Taylor J.Taylor R.Hulse R.Hulse Nobel Prize 1993

Experimental GW Detection Strategies

Two approaches: 1)Resonant bar 2) Interferometry

1) Measurements of the amplitude of oscillations of a resonant bar originated by gravitational wave impinging on the bar

measures spacetime geometry variations detected by free falling masses moving on geodesics using interferometry.

2)Interferometric detection of GWs

Pout =Pin sin2 (2k ΔL) So for fixed ability to measure ΔL, make L as big as possible! FP Cavity Antenna pattern:

Displacement sensitivity can reach ~10-19-10-20 m, then, to measure ΔL/L~10-22 LA and LB should be km long.

Bogdanos et. Al. got six polarizations The polarizations are defined in

• ur 3-space, not in a spacetime

with extra dimensions. Each polarization mode is orthogonal to one another. Note that other modes are not traceless, in contrast to the ordinary plus and cross polarization modes in GR. A prevision from modified theories of gravity! Bogdanos, C.,Capozziello, S., De Laurentis, MF., Nesseris, S. : Massive, massless and ghost modes of gravitational waves from higher-order gravity

• Astrop. Phys 2010

Antenna Pattern

The International Network of GW Detectors

ALLEGRO Baton Rouge LA 1 Bar detector NAUTILUS INFN LNF, Italy Bar detector EXPLORER INFN- CERN Bar detector AURIGA INFN- LNL, Italy Bar detector

shut down

The GW Detectors Network - 2010 Over the years, techniques and sensitivities varied greatly, but since the start it has been clear that to detect gravitational waves we need a NETWORK

13

At the beginning of the ‘90’s, the first groups to build long arm interferometric detectors were born.

TAMA, a 300 m arms interferometer at Mitaka, in Japan, started to operate in 1998. In the same period of time, the GEO detector, a 600 m interferometer, was being built in Hannover, in Germany. The contribution of Resonant Bars has been essential in establishing the field and putting some important upper limits on the gravitational landscape around us, but now the hope for detection is in the Network

• f long arm interferometers.

The experience gained with these machines has been useful for the development of km-size detectors: LIGO and Virgo

The Large Interferometer Network - 2010

TAMA, Tokyo, 300 m GEO, Hannover, 600 m LIGO Hanford, 4 km: 2 ITF on the same site LIGO Livingston, 4 km Virgo, Cascina, 3 km

A more realistic interferometer: from Michelson to Fabry-Perot

 1: the derivative of the output

power is maximum, but the ITF is not a null instrument, i.e. the output is not null when the input is not null (large DC)

 2: dark fringe: no DC if zero input

(in principle...), SNR maximum Two Fabry-Perot cavities (a few kilometers long) plus a power recycling mirror

Seismic Thermal Shot

A Gravitational Interferometer Intrinsic Noise Summary

Frequency (Hz) Strain Spectral Amplitude (Hz) 1/2

• Passive and

Active Attenuators (VIRGO)

Low dissipation materials for mirrors and suspensions High Laser Power, Signal Recycling Techniques Multi-stage pendulum suspension for mirrors, mechanical filter, f >1 Hz Sets lower frequency limit

• n observing.

Make suspension with high-Q so kT is concentrated near 1 Hz pendulum frequency. Need Q~106. Use drawn silica fibres, hydroxide bonding to mirrors

Make mirror substrate of high-Q material so kT energy is concentrated near mode frequencies, above 2 kHz. Need Q~108 in fused silica. Need 100kW of laser power in arms, use power recycling so that laser input (20W)

• nly replaces

mirror losses (10-6 per reflection). Limited by thermal lensing.

Virgo sensitivity Virgo sensitivity More than 7 order

• f magnitude

gained in 6 years! Reached the target sensitivity a part a small difference on low frequency side( 10 Hz) Ligo sensitivity Ligo sensitivity The Goal curve, and actual performance, exceeds the requirement by about a factor of

• three. S1-S5 gained 2.5 order of

magnitude in 4 years

Comparison of VIRGO/LIGO Sensitivities

Thermal noise

1018

Seismic Noise

Superattenuator: filters off the seismic vibrations

Sensitivities of the operated or operating GW antennas.( bars and Tama sketch)(2009)

Horizon definition: according a SNR=8 for a 1.4+1.4 Mo NS binary coalescence It is possible to compute the horizon distance in Mpc Horizon for LIGO and VIRGO around 30 Mpc@100 Hz Horizon for LIGO+ and VIRGO+ around 90 Mpc@100 Hz

• Infrastructure established
• Design Sensitiviy Reached
• Data Analysis paradigms

developed

• Many new upper limits,

important non-detections

Interferometric Detectors Sensitivity Steps:

108
ly Enhanced
LIGO/Virgo+ Virgo/LIGO

Credit:
R.Powell,
B.Berger

Adv.
Virgo/Adv.
LIGO/LCGT

Enhanced Detectors: Now Advanced Detectors (2011-2015) Initial configuration (2001-2008)

• Sensitivity improvement by

a factor 2-3 using some of the Advanced Detectors technologies

• Detection still unlikely, but

surprises possible. A factor of ~10 improvement in linear strain sensitivity over the initial instruments (h of ~3x10-23 in a 100 Hz bw): brings ~103 more candidates into reach=> 10’s–100’s

signals/ year

Improved Network allows to detect position and polarization

• f sources

108
ly Enhanced
LIGO/Virgo+ Virgo/LIGO Adv.
Virgo/Adv.
LIGO/LCGT

NSBH or BHBH

 Rely on stellar evolution

models to predict rate

 Galactic coalescence

rate smaller for BH-NS or BH-BH systems than for NS-NS systems

 Systems with BH can be

seen up to larger distances Detected Rate

 For initial detectors

BHBH ~ 7 10-3/yr NSBH ~ 4 10-3/yr

 For advanced detectors

BHBH ~ 20/yr NSBH ~ 10/yr

Again, large uncertainties on those numbers!!

The GW sources zoo & Results up to now

Compact binary coalescences Continuous waves (pulsars) Bursts Stochastic background

Different approaches to the extraction of the gravitational waveform (for binary systems)

Gravitational wave signals from a neutron star merger (top) in the time (center) and frequency (bottom)

• domains. The chirping in

the gravitational wave is evident in the increased

• scillation frequency

toward the end of the time signal, which peaks in the frequency plot at ~ 6 kHz. Such signals carry information about neutron star equation of state, binary coalescence, and black hole formation. Credits to NASA; (Center, Bottom) Alan Stonebraker, adapted from K. Kiuchi, Y. Sekiguchi, M. Shibata, and

• K. Taniguchi, Phys. Rev.
• Lett. 104, 141101 (2010).

IMR Waveform

Matched Filtering, Templates and All that The FFT allows to extract the signal for all possible arrival times Easy to maximize SNR over the (unknown) time of arrival But you do not know the parameters (masses, spin, angles etc) of the GW signal which is coming, so you need a bank of filters, i.e. a grid of points (with its own resolution) where each point has parameters adapted to the physical expected parameters (templates). These templates are modelled often on hybrid waveforms NR-PN.

The LIGO Scientific Collaboration & The Virgo Collaboration Nature 460, 990-994 (2009) doi:10.1038/nature08278 Comparison of different SGWB measurements and models.

Multi-Wavelength Astronomy

Short GRB are believed to originate from merging of NS/BH, while long GRB should be related to collapsar models, i.e. the collapse of a massive star down to a black hole with the formation of an accretion disk, in a peculiar type of SN-like explosion. No clear understanding yet of how much time delay between a GW emission and a GRB emission (if you ask different experts, you get different numbers!).

 a few seconds (maybe less) for short GRB  minutes or hours for long GRB

A detection of a GW in coincidence with a GRB or a neutrino flux can select between different models! Search for gravitational waves associated with GRB 050915a using the Virgo detector (2008 Class. Quantum Grav. 25 225001, recently put in the highlights

• f the 2008/09 collection)

 A prototype analysis for triggered search using Swift data for a long GRB  of course no detection!, an upper limit on the GW amplitude h~O(10-20)

Hz-1/2 around 200 - 1500 Hz

External Trigger for GW detectors MULTIMESSENGER ASTROPHYSICS

• Swift : multi-wavelength

(optical, UV, Xray) RXTE satellite Space telescope

• Wide-field optical

telescopes: ROTSE, TAROT,SkyMapper

• Radio telescopes: LOFAR
• Neutrino detectors: Antares,

IceCube, LVD, Borexino,Super- Kamiokande

• LARES 2011?
• Millimetron 2015 :

GR probe in connection with ground based GW Interferometric antennas?

LISA - The Laser Interferometer Space Antenna

Three spacecraft in

• rbit about the sun,

with 5 million km baseline The center of the triangle formation will be in the ecliptic plane 1 AU from the Sun and 20 degrees behind the Earth.

LISA (NASA/JPL, ESA) may fly in the next 10 years!

LISA Sensitivity Curve and Astrophysical Sources

 SMBHS: Super Massive Black Holes  EMRI: Extreme Mass-Ratio Inspiral sources  IMRI: Intermediate Mass-Ratio Inspiral sources  Compact binary systems  Stochastic background

DECIGO Bridges the Gap

The Japanese Space Gravitational Wave Antenna - DECIGO Deci-hertz Interferometer Gravitational Wave Observatory

TAMA intend to operate with new Superattenuators mounted for better control and seismic isolation; timing is outlined in the former Table

GEO600 intend to push high frequency sensitivity (new name GEO HF) to much higher level.GEO HF high frequency sensitivity is strongly improved by increasing Intra Cavity Power and by optimizing squeezing. Purpose of GEO HF is also the study

• f advanced techniques to be applied

in future large interferometers with particular reference to signal recycling and squeezing. Timing is outlined in the Time Table I m p r u v e d I N T E R F E R O M E T E R S

• Class. Quantum Grav. 26 (2009)

End 2009 approved

EINSTEIN TELESCOPE

Expected Sensitivity for 3rd generation of ground-based ITFs ET, the Einstein Telescope Detection

• f GWs

events

• n earth

should become routine! built in the underground (not yet known where): 4 interferometers Optimally Oriented and spacedsources angle from time of flight differences

 cryogenic  how to go beyond gravity-gradient noise  and many other technological challenges: Diffused light, E.m. fields

Ground loops, Unforeseen noises, Etc…Last but not the least the necessary budget: A large international collaboration is needed with suitable funding agencies

Final Remarks

• Bar detectors have been the key to open the door to the

development on interferometric detectors

• During the last decade the interferometric technology

began mature: the design sensitivity starting from 10 Hz was reached and an efficient network including Ligo Virgo and Geo was created and is operating. Virgo is opening now the very low frequency region and with the next generation of Advanced Virgo and Ligo the hope is to get the reduction of noise in this very challenging but very important region for the GW sources.

• ET class of interferometers will encompass in an

impressive way the performances of Virgo and Ligo: one day of data taking of ET is equivalent to 106 days of data taking with Virgo and Ligo: We will be on the right to start wit the GW Astronomy

THANK YOU FOR YOUR ATTENTION

There is little doubt that the new window on the universe will finally be cracked open.