每周搜集 arXive 上 Astrophysics（天體物理） 和 General Relativity（廣義相對論）部分與 Gravitational Wave（引力波）相關的文章，方便快速了解學術前言動態。
Astrophysics
[2/15] 識別和處理非平穩LISA噪聲
Identifying and Addressing Nonstationary LISA Noise
Matthew C. Edwards, Patricio Maturana-Russel et al.
https://arxiv.org/pdf/2004.07515.pdf
Abstract. We anticipate noise from the Laser Interferometer Space Antenna (LISA) will exhibit nonstationarities throughout the duration of its mission due to factors such as antenna repointing, cyclostationarities from spacecraft motion, and glitches as highlighted by LISA Pathfinder. In this paper, we use a surrogate data approach to test the stationarity of a time series, with the goal of identifying noise nonstationarities in the future LISA mission. This will be necessary for determining how often the LISA noise power spectral density (PSD) will need to be updated for parameter estimation routines. We conduct a thorough simulation study illustrating the power/size of various versions of the hypothesis tests, and then apply these approaches to differential acceleration measurements from LISA Pathfinder. We also develop a data analysis strategy for addressing nonstationarities in the LISA PSD, where we update the noise PSD over time, while simultaneously conducting parameter estimation, with a focus on planned data gaps. We show that assuming stationarity when noise is nonstationary leads to systematic biases and large posterior variances in parameter estimates for galactic white dwarf binary gravitational wave signals.
[3/15] 用X射線和引力波觀測區分黑洞的吸積和併合生長模型
SEPARATING ACCRETION AND MERGERS IN THE COSMIC GROWTH OF BLACK HOLESWITH X-RAY AND GRAVITATIONAL WAVE OBSERVATIONS
Fabio Pacucci and Abraham Loeb
https://arxiv.org/pdf/2004.07246.pdf
Abstract. The initial seeds of blackholes formed at z ∼ 30 and grew over cosmic time by gas accretion and mergers. Using observational data forquasars and theoretical models for the hierarchical assembly of dark matter halos, we study the relative importanceof gas accretion and mergers for black hole growth, as a function of redshift (0 < z < 10) and black hole mass(10^3 M < M• < 10^10 M). We find that: (i) growth by accretion is dominant in a large fraction of the parameterspace, especially at M• > 10^8 M and z > 6; (ii) growth by mergers is dominant at M• < 10^5 M and z > 5.5,and at M• > 10^8 M and z < 2. As the growth channel has direct implications for the black hole spin (with gasaccretion leading to higher spin values), we test our model against ∼ 20 robust spin measurements available thus far.As expected, the spin tends to decline towards the merger-dominated regime, thereby supporting our model. The nextgeneration of X-ray and GW observatories (e.g. Lynx, Athena and LISA) will map out populations ofblack holes up to very high redshift (z ∼ 20), covering the parameter space investigated here in almost its entirety.Their data will be instrumental to providing a clear picture of how black holes grew across cosmic time.
[4/15] 年輕的大規模和疏散星團中的恆星級質量黑洞及其在引力波產生中的作用: 恆星演化和黑洞自旋模型及與LIGO-Virgo的O1/O2合併事件數據的比較
Stellar-mass black holes in young massive and open stellarclusters and their role in gravitational-wave generation IV:updated stellar-evolutionary and black hole spin modelsand comparisons with the LIGO-Virgo O1/O2merger-event data
Sambaran Banerjee
https://arxiv.org/pdf/2004.07382.pdf
Abstract. In this work, I present a set of full-fledged, long-term, direct, relativistic many-bodycomputations of model dense stellar clusters with up-to-date stellar-evolutionary, supernova (SN), and remnant natal-kick models, including pair instability and pulsationpair instability supernova (PSN and PPSN). These computations utilize NBODY7 Nbody simulation program that is updated with such physical models. The new modelimplementations also incorporate natal spins of black holes (BH), based on theoreticalstellar-evolutionary models, and runtime tracking of general-relativistic (GR) mergerrecoils and final spins of in-spiralling binary black holes (BBH), based on numericalrelativity. These allow, for the first time in a direct N-body simulation, the formation,retention, and participation in GR merger of second-generation BHs. These computations furthermore suggestthat YMCs and OCs produce (semi-)persistent GW sources detectable by LISA fromwithin the ∼ 100 Mpc Local Universe. Such clusters are also capable of producingGR inspirals with eccentricities detectable by the LIGO-Virgo.
General Relativity
[5/15] 量化功率譜密度不確定度對緊緻雙星源引力波參數估計的影響
Quantifying the Effect of Power Spectral Density Uncertainty on Gravitational-Wave Parameter Estimation for Compact Binary Sources
Sylvia Biscoveanu, Carl-Johan Haster, Salvatore Vitale, and Jonathan Davies
https://arxiv.org/pdf/2004.05149.pdf
Abstract. We present a new method to incorporate the uncertainty in the PSD estimation into the Bayesian inference of the binary source parameters. We calculate the PSD for the first 11 GW detections reported by LIGO and Virgo with an on-source method, using only data from the analysis segment to obtain posterior samples for the PSD, which is modeled analytically using the BayesLine algorithm as a sum of a set of Lorentzians and a broadband spline. We demonstrate how to marginalize over the uncertainty encompassed in the full PSD posterior for these first 11 CBC detections and find that incorporating the PSD uncertainty only leads to variations in the positions and width of the binary parameter posteriors on the order of a few percent.
Bound gravitational waves in a dielectric medium and a constant magnetic fieldA.N. Morozov, V.I. Pustovoit, and I.V. Fominhttps://arxiv.org/pdf/2004.05081.pdfAbstract. A description is made of the process of excitation of bound longitudinal-transverse GWs during the propagation of electromagnetic waves in a dielectric medium. It is shown that the speed of such GWs is less than the speed of light in a vacuum and coincides with the speed of an electromagnetic wave in matter. A description of the propagation of a bound GWs in a dielectric in the presence of a constant magnetic field is suggested as well. It is claimed that these GWs in a dielectric medium are forced ones and they cannot exist in a free state.[7/15] 通過引力波探測奇異緻密天體的共振激發態Probing resonant excitations in exotic compact objects via gravitational wavesYasmeen Asali, Peter T. H. Pang, Anuradha Samajdar, and Chris Van Den Broeckhttps://arxiv.org/pdf/2004.05128.pdfAbstract. Exotic compact objects (ECOs) have been proposed that differ from Kerr black holes, and which could leave an imprint upon the GW signal in a variety of ways. Here we consider excitations of ECOs during inspiral, which may occur when the monotonically increasing GW frequency matches a resonant frequency of an exotic object. This causes orbital energy to be taken away, leading to a speed-up of the orbital phase evolution. We show that resonances with induced phase shifts . 10 radians can be detectable with second-generation interferometers, using Bayesian model selection. We apply our methodology to detections in the GWTC-1 catalog from the first and second observing runs of Advanced LIGO and Advanced Virgo, finding consistency with the binary black hole nature of the sources.[8/15] 中頻引力波探測和波源
Mid-Frequency Gravitational Wave Detection and Sources https://arxiv.org/ftp/arxiv/papers/2004/2004.05590.pdfAbstract. A brief history and various themes of mid-frequency GW detection are presented more or less following historical order --- Laser Interferometry, Atom Interferometry (AI), Torsion Bar Antenna (TOBA), and Superconducting Omnidirectional Gravitational Radiation Observatory (SOGRO). Both Earth-based and Space-borne concepts are reviewed with outlook on expected astrophysical sources. Chirality of the gravitational-wave background and pulsar-timing arraysEnis Belgacem and Marc Kamionkowskihttps://arxiv.org/pdf/2004.05480.pdfAbstract. We describe the signatures of a circularly polarized GW background on the timingresiduals obtained with pulsar-timing arrays. Most generally, the circular polarization will dependon the GW direction, and we describe this angular dependence in terms of sphericalharmonics. While the amplitude of the monopole (the overall chirality of the GWbackground) cannot be detected, measures of the anisotropy are theoretically conceivable. Weprovide expressions for the minimum-variance estimators for the circular-polarization anisotropy.We evaluate the smallest detectable signal as a function of the signal-to-noise ratio with which theisotropic GW signal is detected and the number of pulsars (assumed to be roughly uniformly spreadthroughout the sky) in the survey. We find that the overall dipole of the circular polarization anda few higher overall multipoles, are detectable in a survey with >= 100 pulsars if their amplitudeis close to maximal and once the isotropic signal is established with a signal-to-noise ratio >= 400.Even if the anisotropy can be established, though, there will be limited information on its direction.Similar arguments apply to astrometric searches for GWs.[10/15] 在引力波觀測中識別黑洞:在質量間隙雙星中辨別冒名頂替者Recognizing black holes in gravitational-wave observations: Telling apart impostors in mass-gap binariesSayak Datta, Khun Sang Phukon, and Sukanta Bosehttps://arxiv.org/pdf/2004.05974.pdfAbstract. We show how by careful monitoring of the inspiral signal from a compact object binary in groundbased GW detectors one can test if its components are black holes or not. Here we limit ourselves to black holes (with and without spin) in General Relativity. Such objects are characterized by horizons, which absorb gravitational radiation from the orbit during their inspiral in a binary, via a phenomenon known as tidal heating. By contrast, a compact object such as a neutron star has minimal tidal heating – but has tidal deformation – and affects the phase evolution of binaries containing it in a distinctly different way. Here we identify waveform parameters that characterize the strength of tidal heating, and are zero when there is no horizon absorption. We demonstrate how by using those parameters Bayesian methods can distinguish the presence or absence of horizons in a binary. This is a particularly exciting prospect owing to several claims that these stellar-mass objects, with masses heavier than those of neutron stars, may not have a horizon but may be black hole mimickers or exotic compact objects. Perhaps more significant is the possibility that our method can be used to test the presence or absence of horizons in massgap binaries and, thereby, help detect the heaviest neutron star or the lightest black hole. A proper accounting of tidal heating in binary waveform models will also be critical for an unbiased measurement of characteristics of the equation of state of neutron stars in GW observations of binaries containing them – or even to probe the existence of exotic compact objects.[11/15] 利用GW170817對宇宙學和修改引力的聯合檢驗Joint tests of cosmology and modified gravity in light of GW170817S. Mastrogiovanni, D.A. Steer and M. Barsugliahttps://arxiv.org/pdf/2004.06102.pdfAbstract. In this Letter we constrain for the first time both cosmology and modified gravity theories conjointly, by combining the GW and electromagnetic observations of GW170817. We provide joint posterior distributions for the Hubble constant H_0, and two physical effects typical of modified gravity: the gravitational wave (GW) friction, encoded by the parameter α_M, and several GW dispersion relations. Among the results of this analysis, we can improve by 15% the bound of the graviton mass with respect to measurement using the same event, but fixing H0. We obtain a value of m^2_g = 2.08^+13.90_−4.25 ·10^−44 eV^2/c^4 at 99.7% confidence level (CL), when marginalising over the Hubble constant and GW friction term α_M. We find poor constraints on α_M, but demonstrate that for all the GW dispersions relations considered, including massive gravity, the GW must be emitted ∼ 1.74s before the Gamma-ray burst (GRB) and that the GW merger peak group velocity fractional discrepancy from c is <∼ 10^−17.[12/15] 中子星併合殘餘體
Neutron Stars Merger Remnants
Sebastiano Bernuzzi
https://arxiv.org/pdf/2004.06419.pdf
Abstract. Binary neutron star mergers observations are a unique way to constrain fundamental physics and astrophysics at the extreme. The interpretation of GW events and their electromagnetic counterparts crucially rely on general-relativistic models of the merger outcome and remnant properties. Quantitative models can be obtainted only with numerical relativity simulations in 3+1 dimensions that include detailed input physics for the nuclear matter and weak interactions. This review summarizes our current understanding of the merger's remnant focusing on some of the aspects that are relevant for multimessenger observations.
[13/15] 多信使宇宙學：關聯CMB和SGWB的測量Multimessenger Cosmology: correlating CMB and SGWB measurementsPeter Adshead, Niayesh Afshordi et al.https://arxiv.org/pdf/2004.06619.pdfAbstract. Characterizing the physical properties of the stochastic gravitational waves background (SGWB) is a key step towards identifying the nature of its possible origin. We focus our analysis on SGWB anisotropies. The existence of a non-trivial primordial scalar-tensor-tensor (STT) correlation in the squeezed configuration may be inferred from the effect that a long wavelength scalar mode has on the GW power spectrum: an anisotropic contribution. Crucially, such contribution is correlated with temperature anisotropies in the cosmic microwave background (CMB). We show that, for inflationary models that generate suitably large STT non-Gaussianities, cross-correlating the CMB with the stochastic background of GWs is a very effective probe of early universe physics. The resulting signal can be a smoking-gun for primordial SGWB anisotropies.[14/15] 進動雙黑洞主階和次主階諧振模式的高效計算模型Let’s twist again: computationally efficient models for the dominant and sub-dominant harmonic modes of precessing binary black holesGeraint Pratten, Cecilio García-Quirós et al.https://arxiv.org/pdf/2004.06503.pdfAbstract. We present IMRPhenomXPHM, a phenomenological frequency-domain model for the GW signal emitted by quasi-circular precessing binary black holes, which incorporates multipoles beyond the dominant quadrupole in the precessing frame. The model is a precessing extension of IMRPhenomXHM, based on approximate maps between aligned-spin waveform modes in the co-precessing frame and precessing waveform modes in the inertial frame, which is commonly referred to as 「twisting up」 the non-precessing waveforms. IMRPhenomXPHM includes IMRPhenomXP as a special case, the restriction to the dominant quadrupole contribution in the co-precessing frame. We implement two alternative mappings, one based on a single-spin PN approximation, as used in IMRPhenomPv2, and one based on the double-spin MSA approach. We include a detailed discussion of conventions used in the description of precessing binaries and of all choices made in constructing the model. The computational cost of IMRPhenomXPHM is further reduced by extending the interpolation technique to the Euler angles. The accuracy, speed, robustness and modularity of the IMRPhenomX family will make these models productive tools for GW astronomy in the current era of greatly increased number and diversity of detected events.Searching for General Binary Inspirals with Gravitational WavesHorng Sheng Chia and Thomas D. P. Edwardshttps://arxiv.org/pdf/2004.06729.pdfAbstract. We study whether binary black hole template banks can be used to search for the GWs emitted by general binary coalescences. To recover binary signals from noisy data, matched filtering techniques are typically required. This is especially true for low-mass systems, with total mass M<~10M, which can inspiral in the LIGO and Virgo frequency bands for thousands of cycles. In this paper, we focus on the detectability of low-mass binary systems whose individual components can have large spin-induced quadrupole moments and small compactness. The quadrupole contributes to the phase evolution of the waveform whereas the compactness affects the merger frequency of the binary. We find that binary black hole templates (with dimensionless quadrupole κ = 1) cannot be reliably used to search for objects with large quadrupoles (κ >~ 20) over a wide range of parameter space. This is especially true if the general object is highly spinning and has a larger mass than its binary companion. A binary that consists of objects with small compactness could merge in the LIGO and Virgo frequency bands, thereby reducing its accumulated signal-to-noise ratio during the inspiraling regime. Template banks which include these more general waveforms must therefore be constructed. These extended banks would allow us to realistically search for the existence of new astrophysical and beyond the Standard Model compact objects.往期回顧
引力波 arXive 周讀（6-10 Apr 2020）
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