Modeling the Impulsive Noise Component and its Effect on the Operation of a Simple Coherent Network Algorithm for Unmodeled Gravitational Wave Bursts Detection

All-sky search for gravitational-wave bursts in the first joint LIGO-GEO-Virgo run

We present results from an all-sky search for unmodeled gravitational-wave bursts in the data collected by the LIGO, GEO 600 and Virgo detectors between November 2006 and October 2007. The search is performed by three different analysis algorithms over the frequency band 50-6000 Hz. Data are analyzed for times with at least two of the four LIGO-Virgo detectors in coincident operation, with a total live time of 266 days. No events produced by the search algorithms survive the selection cuts. We set a frequentist upper limit on the rate of gravitational-wave bursts impinging on our network of de…

Upper limits on gravitational wave bursts in LIGO's second science run

We perform a search for gravitational wave bursts using data from the second science run of the LIGO detectors, using a method based on a wavelet time-frequency decomposition. This search is sensitive to bursts of duration much less than a second and with frequency content in the 100-1100Hz range. It features significant improvements in the instrument sensitivity and in the analysis pipeline with respect to the burst search previously reported by LIGO. Improvements in the search method allow exploring weaker signals, relative to the detector noise floor, while maintaining a low false alarm rat…

Reflection of electromagnetic waves from mixtures of plane gravitational and scalar waves

We consider colliding wave packets consisting of hybrid mixtures of electromagnetic, gravitational and scalar waves. Irrespective of the scalar field, the electromagnetic wave still reflects from the gravitational wave. Some reflection processes are given for different choice of packets in which the Coulomb-like component $Ψ_2$ vanishes. Exact solution for multiple reflection of an electromagnetic wave from successive impulsive gravitational waves is obtained in a closed form. It is shown that a succesive sign flip in the Maxwell spinor arises as a result of encountering with an impulsive trai…

Method for detecting highly-eccentric binaries with a gravitational wave burst search

Detection of gravitational waves (GW) from highly eccentric binary black hole (BBH) systems can provide insight into their dynamics and formation. To date, all of the LIGO-Virgo BBH detections have been made using quasi-circular templates in their initial discovery. However, recent studies have found some of these systems to be compatible with high eccentricity in the LIGO band, $e_{10 \textrm{Hz}} > 0.1$, possibly pointing to a population of sources that are challenging to detect. Current low-latency search methods used with ground-based GW detector data are not well equipped to detect highly…

带Λ的脉冲引力波的剪切粘贴：数学分析

Cut-and-paste for impulsive gravitational waves with $Λ$: The mathematical analysis

本文对带宇宙常数Λ的脉冲引力波中联系局部Lipschitz度规与分布度规的“不连续坐标变换”进行了严格数学分析，证明了变换后度规属于特定分布类，为物理等价度规提供了严格数学基础。

Impulsive Electromagnetic Emission near a Black Hole

The electromagnetic signature of a point explosion near a Kerr black hole (BH) is evaluated. The first repetitions produced by gravitational lensing are not periodic in time; periodicity emerges only as the result of multiple circuits of the prograde and retrograde light rings and is accompanied by exponential dimming. Gravitational focusing creates a sequence of concentrated caustic features and biases the detection of a repeating source toward alignment of the BH spin with the plane of the sky. We consider the polarization pattern in the case of emission by the Lorentz upboosting and reflect…

Bayesian search for gravitational wave bursts in pulsar timing array data

The nanohertz frequency band explored by pulsar timing arrays provides a unique discovery space for gravitational wave signals. In addition to signals from anticipated sources, such as those from supermassive black hole binaries, some previously unimagined sources may emit transient gravitational waves (a.k.a. bursts) with unknown morphology. Unmodeled transients are not currently searched for in this frequency band, and they require different techniques from those currently employed. Possible sources of such gravitational wave bursts in the nanohertz regime are parabolic encounters of superma…

利用LISA探测银河系中心黑洞双星的引力波暴

Detecting gravitational-wave bursts from black hole binaries in the Galactic Center with LISA

本研究针对围绕银河系中心Sgr A*运行的高偏心率恒星质量黑洞双星，提出基于小波分解的无模型LISA引力波暴搜索方法，可有效获取时频特性并以20%误差推断偏心率，为后续贝叶斯推断约束参数空间。

Validating delta-filters for resonant bar detectors of improved bandwidth foreseeing the future coincidence with interferometers

The classical delta filters used in the current resonant bar experiments for detecting GW bursts are viable when the bandwidth of resonant bars is few Hz. In that case, the incoming GW burst is likely to be viewed as an impulsive signal in a very narrow frequency window. After making improvements in the read-out with new transducers and high sensitivity dc-SQUID, the Explorer-Nautilus have improved the bandwidth ($\sim 20$ Hz) at the sensitivity level of $10^{-20}/\sqrt{Hz}$. Thus, it is necessary to reassess this assumption of delta-like signals while building filters in the resonant bars as …

相对论近心点进动在识别接近偏心双星的第三体存在中的重要性

Importance of relativistic pericenter precession in identifying the presence of a third body near eccentric binaries

本文提出一种改进的定时模型，通过纳入相对论性近心点进动修正，以更准确地检测接近偏心双星的第三体存在。

使用 BayesWave 算法对引力波爆张量偏振的多探测器表征

Multi-detector characterization of gravitational-wave burst tensor polarizations with the BayesWave algorithm

本文使用 BayesWave 算法对比了椭圆和松弛两种张量偏振模型，发现对于多数事件前者因简单而占优，但在高进动多探测器场景下后者更具优势，且能测量通用偏振内容。

Detecting gravitational-wave transients at five sigma: a hierarchical approach

As second-generation gravitational-wave detectors prepare to analyze data at unprecedented sensitivity, there is great interest in searches for unmodeled transients, commonly called bursts. Significant effort has yielded a variety of techniques to identify and characterize such transient signals, and many of these methods have been applied to produce astrophysical results using data from first-generation detectors. However, the computational cost of background estimation remains a challenging problem; it is difficult to claim a 5σ detection with reasonable computational resources without payin…

Implications for the Origin of GRB 070201 from LIGO Observations

We analyzed the available LIGO data coincident with GRB 070201, a short duration hard spectrum gamma-ray burst whose electromagnetically determined sky position is coincident with the spiral arms of the Andromeda galaxy (M31). Possible progenitors of such short hard GRBs include mergers of neutron stars or a neutron star and black hole, or soft gamma-ray repeater (SGR) flares. These events can be accompanied by gravitational-wave emission. No plausible gravitational wave candidates were found within a 180 s long window around the time of GRB 070201. This result implies that a compact binary pr…

Memory, Penrose Limits and the Geometry of Gravitational Shockwaves and Gyratons

The geometric description of gravitational memory for strong gravitational waves is developed, with particular focus on shockwaves and their spinning analogues, gyratons. Memory, which may be of position or velocity-encoded type, characterises the residual separation of neighbouring `detector' geodesics following the passage of a gravitational wave burst, and retains information on the nature of the wave source. Here, it is shown how memory is encoded in the Penrose limit of the original gravitational wave spacetime and a new `timelike Penrose limit' is introduced to complement the original pl…