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## Pierre Binétruy , APC, Paris

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**Overview of LISA signals**Pierre Binétruy, APC, Paris Gravitationalwaves, New frontier, Seoul, 17 January 2013**LISA has become a programme ratherthan a mission:**• LISA Pathfinder • « classic » LISA nowturnedinto « evolved » LISA or eLISA in Europe • post-LISA missions considered in Japan (DECIGO), China, … Meanwhile, someprogress has been made regarding the science of LISA**Verysignificantprogressthese last years in data**analysismethodsthanks to • the Mock LISA Data Challenge • Scientificbreakthrough in numericalrelativitywith the computation of the signal due • to the coalescence of two black holes (« grand challenge » of the 1990s)**The LISA program in Europe has undergone a series of**important reorientationssince 2010: • January 2011: ESA abandons a joint mission with NASA • NGO (New GravitationalwaveObservatory) proposed for selection as L1 mission • (togetherwith the X-ray mission ATHENA and the JUICE mission to the moons of Jupiter) • May 2012: JUICE mission selected as L1 • June 2012: ESA changes the selectionprocess of L missions and announces a call in • 2013/2014 • September 2012: ESA Member States launch the eLISA consortium**LISA redefinitionstudy (2011): the way to eLISA/NGO**• Boundary conditions: • ESA-only mission • cost cap for ESA costat 850 M€ • member state contribution ataround 200M€**Someguidingprinciplesadopted to redefine the LISA mission**NGO: • Keep the sameprinciple of measurement and the samepayload concept • Depart as little as possible fromLISAPathfinder • Optimise the orbit and the launcher: minimize the mass • Simplify the payload Solutions adopted: • Suppression of one of the arms of the triangle: • mother-daughter configuration • Reduction of the armsfrom 5 Mkm to 1 Mkm • New orbitcloser to Earth (drift away) • inertialsensoridentical to LISAPathfinder • nominal mission lifetime: 2 yrs (ext. to 5 yrs)**Science of NGO**Verysignificantwork to identify the potential of possible NGO missions Task force, withstrong US participation to undertake simulations for each possible mission.**Ultra-compact binaries**Provides the «verificationbinaries » i.e. guaranteed sources of gravitationalwaves Detached Double White Dwarfbinary Interacting White Dwarf-Neutron Star binary Out of the 50 known ultra-compact binaries, 8 shouldbedetected in a few weeks to months and couldbeused to check the performance of the instrument. By the time of the launch, severaltensshouldbeknown.**Verificationbinaries**otherbinaries eLISAwilldetect about 3000 WD binariesindividually. Most have orbital periodsbetween 5 and 10 minutes and have experiencedat least one common-envelope phase, whichcanthusbetested. Lightcurve of SDSS J0651+28 eLISAwillconstrain the physics of tides in WD and mass transferstability Tidal distortion of a primary white dwarf**Strain amplitude**. Thus the measurement of h, f and f willprovide a determination of distance D and chirp mass M. eLISAwillmeasure the sky position and distance of severalhundredbinaries, constraining the mass distribution in the Galaxy. For severalhundred sources, itwilldetermine the orbital inclination to betterthan 10°, allowing to test if they are statisticallyalignedwith the Galacticdisk. The millions of ultra-compact binariesthatwill not be individuallydetectedwillform a detectableforeground fromwhich the global properties of the whole population canbedetermined.**Massive black holes**There seems to exist a close connectionbetween galaxies and their central black hole whichleads to thinkthattheyevolvedjointly M= 104to105M M= 106to107M « mergertreehistory »**Direct collapse**Pop III remnants**NGO willallow to study black holes of mass 104 à 105Mup**to redshifts 15 à 20**NGO willallow to observe individually the coalescence of two**massive black holes resultingfrom the collision of their host galaxies, passing through the « inspiral », « merger » and « ringdown » phases.**Test of the stronggravityregime**Plunge Merger Ringdown GR: postNewtonian approximation BH perturbation theory GR: numericalrelativity severalquasinormal modes observed LGW = 1023 L**Parameter estimation: Fischer matrixresults**A. Sesana @ LISA Symposium**EMRI (Extreme Mass Ratio Inspiral)**Gravitationalwavesproduced by massive objects (mass 10 to 100 M) fallinginto the horizon of a supermassive black holeallow to identify in a unique way the geometry of space-time, to identify the characteristics of the black hole and to verify the predictions of GR.**Stellar-mass BH capture by a massive BH: dozens per year to**z~0.7. • We have measured the mass of the GC BH using a few stars and with at most 1 orbit each, still far from horizon. • Imagine the accuracy when we have 105 orbits very close to horizon! GRACE/GOCE for massive BHs. • Prove horizon exists. • Test the no-hair theorem to 1%. • Measure masses of holes to 0.1%, spin of central BH to 0.001. • Population studies of central and cluster BHs. • Find IMBHs: captures of 103 MoBHs.**Confronting General Relativity**☺ No hairhypothesis • A Kerr black holeischaracterized by its mass and spin: detectingtwo or more quasinormal modes (2 parameters • for each normal mode) in the ringdown phase willallow to check that the objectisdescribedonly by 2 independent • numbers. • EMRI willallow to do precisegeodesy and again to check that the mass, spin and quadrupole moment of the • central object are consistent with Kerr geometry: • Define mass moments Ml and mass-currentmultipole moments Sl (a ≣ S/M Kerr spin parameter) • Ml + iSl = (ia)l M⇒ M0 = M, S1 = aM, quadrupole moment M2=-a2 M =-S2/M, … • With SNR of 30, ΔM0 /Mand ΔS1 /M2are of order 10-3 to 10-4, • while ΔM2/ M3 ∼ 10-2to 10-4 BarackCutler gr-qc/0612029 Graviton mass eLISAwillbe able to set an upperlimit on the graviton thatis four orders of magnitude betterthan the existing 4.10-22 eV.**Cosmological backgrounds**cosmic strings****In the mother-daughter configuration, loss of Sagnac mode whichallowed to « dig » into the sensitivitycurve Bender, Hogan astro-ph/0104266 d d M SeealsoLittenberg, Cornish 1008.1577[gr-qc]**Still possible to detect stochastic backgrounds if they have**a frequency dependence different from the background. Hence effort to understand not only the amplitude of cosmological background but also the nature of their frequency dependence and how generic it is. ☺**First order phase transition**nucleationof true vacuum bubbles inside the false vacuum The Terascaleregion (E ∼ TeV to 104TeV) lies precisely in the LISA frequencywindow Collision of bubbles and (MHD) turbulence production of gravitational waves**It remains to beseenwhetherthisapplies to the electroweak**phase transition, given the results on the Higgs.**Background induced by cosmic or fundamental strings**parameteris string tension μ, or rather GNμ. Large loop scenario (at production, the size L of loopsis a fraction of the horizon L = αdH≈ αt) Small loop scenario (α = 50 Gμ ε, ε << 1)**Towards a multi-wavelengthanalysis?**VIRGO aVIRGO See P.B., A. Bohe, J.-F. Dufaux and C. Caprini 1201.0983**Using MBH coalescence to do cosmography(e.g. measure the**equation of state of darkenergy (m1 m2)3/5 Key parameter : chirp mass M = (z) (1+z) (m1 + m2)1/5 Amplitude of the gravitationalwave in the inspiral phase: frequency f(t) = d/2dt B. Schutz M(z)5/3 f(t)2/3 h(t) = F(angles) cos (t) dL Luminosity distance poorlyknown in the case of LISA, worse for eLISA 10 arcmin 1 Hz ~ SNR fGW**Whenboth a measure of the direction and of the redshift are**allowed Holz and Hughes 0.5% dL/dL delensingmethods? But beware of gravitationallensing! Can one identify the host galaxy (and thus z)? Use subdominant signal harmonics () to narrow the LISA window Broeck, Trias, Sathyaprakash, Sintes 1001.3099 Enforcestatisticalconsistencywithcosmologicalparameterdetermination for all possible hosts Petiteau, Babak, Sesana 1102.0769**To conclude, listpresented by B. Schutz at the L1 selection:**• Massive BHs (105--107 Mo) • Measurement of mass at z = 1 to ±0.1%, spin a/M to ±0.01. • Mass function, central cluster of black holes in ordinary galaxies to z = 0.5. • Evolution of the Cosmic Web at high redshift • Observation of objects before re-ionisation: BH mergers at z >> 10. • Testing models of how massive BHs formed and evolved from seeds. • Compact WD binaries in the Galaxy • Catalogue ~2000 new white-dwarf binary systems in the Galaxy. • Precise masses & distances for dozens of systems + all short-period NS-BHs. • Fundamental physics and testing GR • Ultra-strong GR: Prove horizon exists; test no-hair theorem, cosmic censorship; search for scalar gravitational fields, other GR breakdowns. • Fundamental physics: look for cosmic GW background, test the order of the electroweak phase transition, search for cosmic strings.**ESA Space Science AdvisoryCommitteerecommendations**earliestlaunch date for NGO: 2025 to 2028 • NGO unanimouslyrecognized first from point of view of • scientific importance, • strategic value, • strategic importance for Europe.**eLISA Science Working Groups**• ultra-compact binaries • astrophysical black holes • EMRI • cosmology: backgrounds, cosmography, formation of large structures • tests of fundamentallaws • data analysis • science of measurement**eLISAwebite**http://www.elisa-ngo.org/