Theory-Agnostic Constraints on Black-Hole Dipole Radiation with Multi-Band Gravitational-Wave Astrophysics
Enrico Barausse, Nicolas Yunes, Katie Chamberlain
备注：
6 pages, 1 figure; slight changes to text and figure (which now uses design aLIGO instead of current aLIGO for the combined eLISA-aLIGO costraints), conclusions unchanged. Matches version accepted by PRL
The aLIGO detection of the black-hole binary GW150914 opened a new era for probing extreme gravity. Many gravity theories predict the emission of dipole gravitational radiation by binaries. This is excluded to high accuracy in binary pulsars, but entire classes of theories predict this effect predominantly (or only) in binaries involving black holes. Joint observations of GW150914-like systems by aLIGO and eLISA will improve bounds on dipole emission from black-hole binaries by six orders of magnitude relative to current constraints, provided that eLISA is not dramatically descoped.
One of the main pillars of the ΛCDM model is the Cosmological Principle, which states that our Universe is statistically isotropic and homogeneous on large scales. Here we test this hypothesis using the Astrophysical Gravitational Wave Background (AGWB) expected to be measured by the Einstein Telescope-Cosmic Explorer network; in particular we perform a numerical computation of the AGWB dipole, evaluating the intrinsic contribution due to clustering and the kinematic effect induced by the observer motion. We apply a component separation technique in the GW context to disentangle the kinematic …
A Four-dimensional Model-agnostic Probe into the Astrophysical Origins of Binary Black Hole Subpopulations
Northwestern University（西北大学）；NSF-Simons AI Institute for the Sky (SkAI)（美国国家科学基金会-西蒙斯人工智能天空研究所）；Department of Physics and Astronomy, Northwestern University（西北大学物理与天文学系）
We analyze a new class of static exact solutions of Einstein-Maxwell-Dilaton gravity with arbitrary scalar coupling constant $α$, representing a gravitational body endowed with electromagnetic dipole moment. This class possesses mass, dipole and scalar charge parameters. A discussion of the geodesic motion shows that the scalar field interaction is so weak that it cannot be measured in gravitational fields like the sun, but it could perhaps be detected in gravitational fields like pulsars. The scalar force can be attractive or repulsive. This gives rise to the hypothesis that the magnetic fiel…
Constraining Dipole Radiation with Multiband Gravitational Waves from Eccentric Binary Black Holes
Kavli Institute for Astronomy and Astrophysics, Peking University（北京大学科维理天文与天体物理研究所）；National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台）
We remind that the ring down features observed in the LIGO GWs resulted from trembling of photon spheres (Rp=3M) of newly formed compact objects and not from the trembling of their event horizons (R=2M). Further, the tentative evidences for late time echoes in GWs might be signatures of horizonless compact objects rather than vacuum black holes (BHs). Similarly, even for an ideal BH, the radius of its shadow is R_shad = \sqrt{3}Rp is actually the gravitationally lensed shadow of its photon sphere. Accordingly any compact object having R \geq R = 3M would generate similar shadow. Thus, no obser…
Gravitational waves from the coalescence of binary black holes can be distinguished from noise transients in a detector network through Bayesian model selection by exploiting the coherence of the signal across the network. We present a Bayesian framework for calculating the posterior probability that a signal is of astrophysical origin, agnostic to the specific search strategy, pipeline or search domain with which a candidate is identified. We apply this framework under \textit{identical} assumptions to all events reported in the LIGO-Virgo GWTC-1 catalog, GW190412 and numerous event candidate…
Dipole gravitational disturbances from gravitationally unbound mass quadrupoles propagate to the radiation zone with signal strength at least of quadrupole order if the quadrupoles are nonrelativistic, and of dipole order if relativistic. Angular distributions of parallel-polarized and transverse-polarized dipole power in the radiation zone are calculated for simple unbound quadrupoles, like a linear-oscillator/stress-wave pair and a particle storage ring. Laboratory tests of general relativity through measurements of dipole gravity waves in the source region are proposed. A NASA G2 flywheel m…
Compact objects in general relativity approximately move along geodesics of spacetime. It is shown that the corrections to geodesic motion due to spin (dipole), quadrupole, and higher multipoles can be modeled by an extension of the point mass action. The quadrupole contributions are discussed in detail for astrophysical objects like neutron stars or black holes. Implications for binaries are analyzed for a small mass ratio situation. There quadrupole effects can encode information about the internal structure of the compact object, e.g., in principle they allow a distinction between black hol…
Gravitational wave observations of compact binary mergers are already providing stringent tests of general relativity and constraints on modified gravity. Ground-based interferometric detectors will soon reach design sensitivity and they will be followed by third-generation upgrades, possibly operating in conjunction with space-based detectors. How will these improvements affect our ability to investigate fundamental physics with gravitational waves? The answer depends on the timeline for the sensitivity upgrades of the instruments, but also on astrophysical compact binary population uncertain…
Model-agnostic search of gravitational wave echoes in LVK data
Hangzhou Institute for Advanced Study, UCAS（杭州高等研究院）；University of Chinese Academy of Sciences（中国科学院大学）；Institute of High Energy Physics, Chinese Academy of Sciences（高能物理研究所）；School of Physics Sciences, University of Chinese Academy of Sciences（中国科学院大学物理科学学院）；Institute of Theoretical Physics, Chinese Academy of Sciences（理论物理研究所）；Center for High Energy Physics, Peking University（北京大学高能物理中心）
The observation of the shadow of the supermassive black hole M87$^{*}$ by the Event Horizon Telescope (EHT) is sensitive to the spacetime geometry near the circular photon orbit and beyond, and it thus has the potential to test general relativity in the strong field regime. Obstacles to this program, however, include degeneracies between putative deviations from general relativity and both the description of the accretion flow and the uncertainties on "calibration parameters", such as e.g. the mass and spin of the black hole. In this work, we introduce a formalism, based on a principal compone…
A New Paradigm for Testing Gravity: Theory-Independent Constraints Using Data From All Astrophysical and Cosmological Scales
Jodrell Bank Centre for Astrophysics, University of Manchester（曼彻斯特大学乔德雷尔银行天体物理学中心）；Department of Physics and Astronomy, Queen Mary University of London（伦敦大学玛丽女王学院物理与天文系）
White dwarfs (WDs) and neutron stars (NSs) are among the most magnetized astrophysical objects in the universe, with magnetic fields that can reach up to $10^9\,\mathrm{G}$ for WDs and up to $10^{15}\,\mathrm{G}$ for NSs. The galaxy is expected to be populated with approximately one hundred million of double WD and millions of NS-WD binaries. Throughout the duration of the mission, the Laser Interferometer Space Antenna (LISA) will observe gravitational waves (GWs) emitted simultaneously by more than ten thousand of such galactic binaries. In this paper, we investigate the effect of the magnet…
Nowhere left to hide: revealing realistic gravitational-wave populations in high dimensions and high resolution with PixelPop
LIGO Laboratory, Massachusetts Institute of Technology（麻省理工学院引力波实验室）；Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology（麻省理工学院卡弗里天体物理与空间研究研究所）；Department of Physics, Massachusetts Institute of Technology（麻省理工学院物理系）；Nottingham Centre of Gravity & School of Mathematical Sciences, University of Nottingham（诺丁汉大学重力研究中心与数学科学学院）
X-ray reflection spectroscopy is a powerful technique for probing the nature of gravity around black holes in the so-called strong field regime. One of the most popular of such probes is to look at theory-agnostic deviations away from the Kerr solution, which is the only astrophysically relevant black hole solution within classical general relativity, in order to verify whether astrophysical black holes are described by the Kerr metric. We have recently extended our X-ray reflection spectroscopy framework to a class of very general axisymmetric non-Kerr black holes proposed by Konoplya, Rezzol…
Gravitational waves emitted from compact binary coalescence can be subject to wave diffraction if they are gravitationally lensed by an intervening mass clump whose Schwarzschild timescale matches the wave period. Waves in the ground-based frequency band $f\sim 10$--$10^3\,$Hz are sensitive to clumps with masses $M_E \sim 10^2$--$10^3\,M_\odot$ enclosed within the impact parameter. These can be the central parts of low mass $M_L \sim 10^3$--$10^6\,M_\odot$ dark matter halos, which are predicted in Cold Dark Matter scenarios but are challenging to observe. Neglecting finely-tuned impact paramet…
It is still an open issue if astrophysical black holes have electric charges or not. In this work, we analytically calculate gravitational and electromagnetic waveforms in the frequency domain for charged black hole binaries during the inspiral phase. In addition to the well-known $f^{-7/6}$ waveforms, we also get a $-11/6$ power law gravitational wave component. The phase of waveforms for charged binary is fully derived. In the case of electromagnetic counterparts, we focus on the electromagnetic dipole radiation, but we include the quadrupole contribution to complete our discussion. We also …
We study the motion of electrically charged particles, magnetic monopoles, and magnetic dipoles around electrically and magnetically charged stringy black holes. From the analysis of the radius of the innermost stable circular orbit (ISCO) of electrically charged particles, we show that the electric charge $Q$ of stringy black holes can mimic well the spin of Kerr black holes; the black hole magnetic charge $Q_m$ can mimic spins up to $a_* \simeq 0.85$ for magnetic dipoles; the magnetic charge parameter $g$ of a magnetic monopole can mimic spins up to $a_* \simeq 0.8$. This is due to the destr…
