002211867 001__ 2211867
002211867 003__ SzGeCERN
002211867 005__ 20231004093558.0
002211867 0247_ $$2DOI$$a10.1103/PhysRevD.94.084031
002211867 0248_ $$aoai:cds.cern.ch:2211867$$pcerncds:FULLTEXT$$pcerncds:CERN:FULLTEXT$$pcerncds:CERN
002211867 035__ $$9arXiv$$aoai:arXiv.org:1608.08637
002211867 035__ $$9Inspire$$a1484629
002211867 037__ $$9arXiv$$aarXiv:1608.08637$$cgr-qc
002211867 041__ $$aeng
002211867 100__ $$aCardoso, Vitor$$uCERN$$uPerimeter Inst. Theor. Phys.$$uLisbon, IST$$uLisbon, CENTRA$$vTheoretical Physics Department, CERN , CH-1211 Geneva 23, Switzerland$$vPerimeter Institute for Theoretical Physics , 31 Caroline Street North Waterloo, Ontario N2L 2Y5, Canada$$vCENTRA, Departamento de Física, Instituto Superior Técnico—IST, Universidade de Lisboa—UL , Avenida Rovisco Pais 1, 1049 Lisboa, Portugal
002211867 245__ $$aGravitational-wave signatures of exotic compact objects and of quantum corrections at the horizon scale
002211867 246__ $$aEchoes of ECOs: gravitational-wave signatures of exotic compact objects and of quantum corrections at the horizon scale
002211867 269__ $$c30 Aug 2016
002211867 260__ $$c2016-10-21
002211867 300__ $$a13 p
002211867 500__ $$9arXiv$$a13 pages, RevTex4. v2: typo in equation 7 corrected, references added, to appear in PRD
002211867 520__ $$aGravitational waves from binary coalescences provide one of the cleanest signatures of the nature of compact objects. It has been recently argued that the post-merger ringdown waveform of exotic ultracompact objects is initially identical to that of a black-hole, and that putative corrections at the horizon scale will appear as secondary pulses after the main burst of radiation. Here we extend this analysis in three important directions: (i)~we show that this result applies to a large class of exotic compact objects with a photon sphere for generic orbits in the test-particle limit; (ii)~we investigate the late-time ringdown in more detail, showing that it is universally characterized by a modulated and distorted train of "echoes" of the modes of vibration associated with the photon sphere; (iii)~we study for the first time equal-mass, head-on collisions of two ultracompact boson stars and compare their gravitational-wave signal to that produced by a pair of black-holes. If the initial objects are compact enough as to mimic a binary black-hole collision up to the merger, the final object exceeds the maximum mass for boson stars and collapses to a black-hole. This suggests that --~in some configurations~-- the coalescence of compact boson stars might be almost indistinguishable from that of black-holes. On the other hand, generic configurations display peculiar signatures that can be searched for in gravitational-wave data as smoking guns of exotic compact objects.
002211867 520__ $$9APS$$aGravitational waves from binary coalescences provide one of the cleanest signatures of the nature of compact objects. It has been recently argued that the postmerger ringdown waveform of exotic ultracompact objects is initially identical to that of a black hole, and that putative corrections at the horizon scale will appear as secondary pulses after the main burst of radiation. Here we extend this analysis in three important directions: (i) we show that this result applies to a large class of exotic compact objects with a photon sphere for generic orbits in the test-particle limit; (ii) we investigate the late-time ringdown in more detail, showing that it is universally characterized by a modulated and distorted train of “echoes”of the modes of vibration associated with the photon sphere; (iii) we study for the first time equal-mass, head-on collisions of two ultracompact boson stars and compare their gravitational-wave signal to that produced by a pair of black holes. If the initial objects are compact enough as to mimic a binary black-hole collision up to the merger, the final object exceeds the maximum mass for boson stars and collapses to a black hole. This suggests that—in some configurations—the coalescence of compact boson stars might be almost indistinguishable from that of black holes. On the other hand, generic configurations display peculiar signatures that can be searched for in gravitational-wave data as smoking guns of exotic compact objects.
002211867 520__ $$9arXiv$$aGravitational waves from binary coalescences provide one of the cleanest signatures of the nature of compact objects. It has been recently argued that the post-merger ringdown waveform of exotic ultracompact objects is initially identical to that of a black-hole, and that putative corrections at the horizon scale will appear as secondary pulses after the main burst of radiation. Here we extend this analysis in three important directions: (i) we show that this result applies to a large class of exotic compact objects with a photon sphere for generic orbits in the test-particle limit; (ii) we investigate the late-time ringdown in more detail, showing that it is universally characterized by a modulated and distorted train of "echoes" of the modes of vibration associated with the photon sphere; (iii) we study for the first time equal-mass, head-on collisions of two ultracompact boson stars and compare their gravitational-wave signal to that produced by a pair of black-holes. If the initial objects are compact enough as to mimic a binary black-hole collision up to the merger, the final object exceeds the maximum mass for boson stars and collapses to a black-hole. This suggests that - in some configurations - the coalescence of compact boson stars might be almost indistinguishable from that of black-holes. On the other hand, generic configurations display peculiar signatures that can be searched for in gravitational-wave data as smoking guns of exotic compact objects.
002211867 540__ $$aarXiv nonexclusive-distrib. 1.0$$barXiv$$uhttp://arxiv.org/licenses/nonexclusive-distrib/1.0/
002211867 540__ $$3publication$$aCC-BY-3.0
002211867 542__ $$3publication$$dThe Author(s)$$g2016
002211867 595__ $$aLANL EDS
002211867 65017 $$2arXiv$$aGeneral Relativity and Cosmology
002211867 65027 $$2arXiv$$aParticle Physics - Theory
002211867 65027 $$2arXiv$$bParticle Physics - Phenomenology
002211867 65027 $$2arXiv$$bAstrophysics and Astronomy
002211867 695__ $$9LANL EDS$$agr-qc
002211867 695__ $$9LANL EDS$$aastro-ph.HE
002211867 695__ $$9LANL EDS$$ahep-ph
002211867 695__ $$9LANL EDS$$ahep-th
002211867 690C_ $$aARTICLE
002211867 690C_ $$aCERN
002211867 700__ $$aHopper, Seth$$uLisbon, CENTRA$$uLisbon, IST$$vCENTRA, Departamento de Física, Instituto Superior Técnico—IST, Universidade de Lisboa—UL , Avenida Rovisco Pais 1, 1049 Lisboa, Portugal
002211867 700__ $$aMacedo, Caio F. B.$$uLisbon, IST$$uLisbon, CENTRA$$vCENTRA, Departamento de Física, Instituto Superior Técnico—IST, Universidade de Lisboa—UL , Avenida Rovisco Pais 1, 1049 Lisboa, Portugal
002211867 700__ $$aPalenzuela, Carlos$$uU. Iles Balears, Palma$$vDepartament de Física & IAC3, Universitat de les Illes Balears and Institut d’Estudis Espacials de Catalunya , Palma de Mallorca, Baleares E-07122, Spain
002211867 700__ $$aPani, Paolo$$uLisbon, CENTRA$$uINFN, Rome$$uLisbon, IST$$uRome U.$$vDipartimento di Fisica, “Sapienza” Università di Roma & Sezione INFN Roma1 , P.A. Moro 5, 00185, Roma, Italy$$vCENTRA, Departamento de Física, Instituto Superior Técnico—IST, Universidade de Lisboa—UL , Avenida Rovisco Pais 1, 1049 Lisboa, Portugal
002211867 773__ $$c084031$$oPhys. Rev. D 94, 084031 (2016)$$pPhys. Rev. D$$v94$$y2016
002211867 8564_ $$uhttp://arxiv.org/pdf/1608.08637.pdf$$yPreprint
002211867 8564_ $$81251861$$s582266$$uhttps://cds.cern.ch/record/2211867/files/PhysRevD.94.084031.pdf$$yAPS Open Access article
002211867 8564_ $$81251861$$s1779648$$uhttps://cds.cern.ch/record/2211867/files/PhysRevD.94.084031.pdf?subformat=pdfa$$xpdfa$$yAPS Open Access article
002211867 8564_ $$81303056$$s804476$$uhttps://cds.cern.ch/record/2211867/files/arXiv:1608.08637.pdf
002211867 8564_ $$81303049$$s6042$$uhttps://cds.cern.ch/record/2211867/files/psi4_headon_medmass.png$$y00008 GW (i.e., represented by the $l=m=2$ mode of the Newman-Penrose $\Psi_4$ scalar), as a function of time, emitted during the head-on collision of two solitonic BSs. Left panel {\em (low mass)}: The final object is not massive enough to collapse to a BH, so the final fate of the system will depend on the BS configuration; a perturbed BS (bs-bs), annihilation of the stars (bs-abs) or two individual stars after multiple inelastic collisions (bs-bsop). Right panel {(\em medium mass)}: The final object promptly collapses to a BH, although previously --for some of the configurations, i.e., the bs-bs and the bs-abs-- there is a signature on the GWs produced by the scalar field interaction.
002211867 8564_ $$81303050$$s29830$$uhttps://cds.cern.ch/record/2211867/files/WH_nolightring.png$$y00005 GW signal produced by a test particle falling radially into a wormhole with $E=1.01$. We consider the same setup as in Ref.~\cite{Cardoso:2016rao} but for a wormhole without a PS. Without outer (and inner) PS, the ringdown signal is, clearly, different from that of a BH. Because there is no longer a good resonating cavity, echoes do not appear to be excited.
002211867 8564_ $$81303051$$s45854$$uhttps://cds.cern.ch/record/2211867/files/scattering_zoom.png$$y00002 Left: A dipolar ($l=1,m=0$) scalar wavepacket scattered off a Schwarzschild BH and off different ECOs with $\ell=10^{-6} M$ ($r_0=2.000001 M$). The right panel shows the late-time behavior of the waveform. The result for a wormhole, a gravastar, and a simple empty shell of matter are qualitatively similar and display a series of ``echoes'' which are modulated in amplitude and distorted in frequency. For this compactness, the delay time in Eq.~\eqref{Deltat} reads $\Delta t\approx 110 M$ for wormholes, $\Delta t\approx 82 M$ for gravastars, and $\Delta t\approx 55 M$ for empty shells, respectively.
002211867 8564_ $$81303052$$s5292$$uhttps://cds.cern.ch/record/2211867/files/phi2max_headon_lowmass.png$$y00009 Maximum value of the scalar field norm, as a function of time, for the head-on collision of two low-mass solitonic BSs. The bs-bs collision forms, after a relatively long transient, a single perturbed BS. The bs-abs configuration has opposite Noether charges that annihilate soon after they merge, destroying the stars and dispersing/radiating their scalar fields. The scalar field interaction in the bs-bsop is repulsive and larger than the gravitational attraction, so the system undergoes several inelastic collisions --which compresses the star and leads to small bumps on the scalar field norm that can be observed at $t\approx \{60,160,240\}$-- before relaxing to a binary at rest with the surfaces barely touching.
002211867 8564_ $$81303053$$s12472$$uhttps://cds.cern.ch/record/2211867/files/mass_radius_BS.png$$y00006 Mass-radius relation for a solitonic BS with $\sigma_0=0.05m_P$. In the inset we show the compactness as a function of the central scalar field, $\sigma_c\equiv|\Phi(r=0)|$. The red and the green markers correspond, respectively, to the light BSs with $M/R\approx 0.118$ and to the medium-mass one with $M/R\approx 0.184$ whose numerical evolutions are discussed in the main text. The blue marker indicates a stable BS with nearly maximum mass and $M/R\approx 1/3$. The horizontal line in the right panel denotes the compactness of the Schwarzschild PS, $M/R=1/3$.
002211867 8564_ $$81303054$$s17066$$uhttps://cds.cern.ch/record/2211867/files/WH.png$$y00003 Left panel: The waveform for the radial infall of a particle with specific energy $E = 1.5$ into a wormhole with $\ell=10^{-6} M$, compared to the BH case. The BH ringdown, caused by oscillations of the outer PS as the particle crosses through, are also present in the wormhole waveform. A part of this pulse travels inwards and is absorbed by the event horizon (for BHs) or then bounces off the inner (centrifugal or PS) barrier for ECOs, giving rise to echoes of the initial pulse. This is a low-pass cavity which cleans the pulse of high-frequency components. At late times, only a lower frequency, long-lived signal is present, well described by the QNMs of the ECO. Right panel: the same for a scattering trajectory, with pericenter $r_{\rm min} = 4.3M$, off a wormhole with $\ell= 10^{-6} M$. The main pulse is generated now through the bremsstrahlung radiation emitted as the particle approaches the pericenter. The remaining main features are as before. We show only the real part of the waveform, the imaginary part displays the same qualitative behavior.
002211867 8564_ $$81303055$$s42166$$uhttps://cds.cern.ch/record/2211867/files/WH_scatter.png$$y00004 Left panel: The waveform for the radial infall of a particle with specific energy $E = 1.5$ into a wormhole with $\ell=10^{-6} M$, compared to the BH case. The BH ringdown, caused by oscillations of the outer PS as the particle crosses through, are also present in the wormhole waveform. A part of this pulse travels inwards and is absorbed by the event horizon (for BHs) or then bounces off the inner (centrifugal or PS) barrier for ECOs, giving rise to echoes of the initial pulse. This is a low-pass cavity which cleans the pulse of high-frequency components. At late times, only a lower frequency, long-lived signal is present, well described by the QNMs of the ECO. Right panel: the same for a scattering trajectory, with pericenter $r_{\rm min} = 4.3M$, off a wormhole with $\ell= 10^{-6} M$. The main pulse is generated now through the bremsstrahlung radiation emitted as the particle approaches the pericenter. The remaining main features are as before. We show only the real part of the waveform, the imaginary part displays the same qualitative behavior.
002211867 8564_ $$81303057$$s582266$$uhttps://cds.cern.ch/record/2211867/files/10.1103_PhysRevD.94.084031.pdf$$yFulltext
002211867 8564_ $$81303058$$s7693$$uhttps://cds.cern.ch/record/2211867/files/psi4_headon_lowmass.png$$y00007 GW (i.e., represented by the $l=m=2$ mode of the Newman-Penrose $\Psi_4$ scalar), as a function of time, emitted during the head-on collision of two solitonic BSs. Left panel {\em (low mass)}: The final object is not massive enough to collapse to a BH, so the final fate of the system will depend on the BS configuration; a perturbed BS (bs-bs), annihilation of the stars (bs-abs) or two individual stars after multiple inelastic collisions (bs-bsop). Right panel {(\em medium mass)}: The final object promptly collapses to a BH, although previously --for some of the configurations, i.e., the bs-bs and the bs-abs-- there is a signature on the GWs produced by the scalar field interaction.
002211867 8564_ $$81303059$$s39276$$uhttps://cds.cern.ch/record/2211867/files/scattering.png$$y00001 Left: A dipolar ($l=1,m=0$) scalar wavepacket scattered off a Schwarzschild BH and off different ECOs with $\ell=10^{-6} M$ ($r_0=2.000001 M$). The right panel shows the late-time behavior of the waveform. The result for a wormhole, a gravastar, and a simple empty shell of matter are qualitatively similar and display a series of ``echoes'' which are modulated in amplitude and distorted in frequency. For this compactness, the delay time in Eq.~\eqref{Deltat} reads $\Delta t\approx 110 M$ for wormholes, $\Delta t\approx 82 M$ for gravastars, and $\Delta t\approx 55 M$ for empty shells, respectively.
002211867 8564_ $$81303060$$s19779$$uhttps://cds.cern.ch/record/2211867/files/potential.png$$y00000 Qualitative features of the effective potential felt by perturbations of a Schwarzschild BH compared to the case of wormholes~\cite{Cardoso:2016rao} and of star-like ECOs with a regular center~\cite{Cardoso:2014sna}. The precise location of the center of the star is model-dependent and was chosen for visual clarity. The maximum and minimum of the potential corresponds approximately to the location of the unstable and stable PS, and the correspondence is exact in the eikonal limit of large angular number $l$. In the wormhole case, modes can be trapped between the PSs in the two ``universes''. In the star-like case, modes are trapped between the PS and the centrifugal barrier near the center of the star~\cite{1991RSPSA.434..449C,Chandrasekhar:1992ey,Abramowicz:1997qk}. In all cases the potential is of finite height, and the modes leak away, with higher-frequency modes leaking on shorter timescales.
002211867 916__ $$sn$$w201635
002211867 960__ $$a13
002211867 980__ $$aARTICLE