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