Binary Black Hole Merger GW150914 Research Articles

Accelerating tests of general relativity with gravitational-wave signals using hybrid sampling

The Advanced LIGO/Virgo interferometers have observed $\ensuremath{\sim}100$ gravitational-wave transients enabling new questions to be answered about relativity, astrophysics, and cosmology. However, many of our current procedures for computing these constraints will not scale well with the increased size of future transient catalogs. We introduce a novel hybrid sampling method in order to more efficiently perform parameterized tests of general relativity with gravitational-wave signals. Applying our method to the binary black hole merger GW150914 and simulated signals we find that our method is approximately an order of magnitude more efficient than the current method with conservative settings for our hybrid analysis. While we have focused on the specific problem of measuring potential deviations from relativity, our method is of much wider applicability to any problem that can be decomposed into a simple and more complex model(s).

Gravitational wave denoising of binary black hole mergers with deep learning

Gravitational wave detection requires an in-depth understanding of the physical properties of gravitational wave signals, and the noise from which they are extracted. Understanding the statistical properties of noise is a complex endeavor, particularly in realistic detection scenarios. In this article we demonstrate that deep learning can handle the non-Gaussian and non-stationary nature of gravitational wave data, and showcase its application to denoise the gravitational wave signals generated by the binary black hole mergers GW150914, GW170104, GW170608 and GW170814 from advanced LIGO noise. To exhibit the accuracy of this methodology, we compute the overlap between the time-series signals produced by our denoising algorithm, and the numerical relativity templates that are expected to describe these gravitational wave sources, finding overlaps O≳0.99. We also show that our deep learning algorithm is capable of removing noise anomalies from numerical relativity signals that we inject in real advanced LIGO data. We discuss the implications of these results for the characterization of gravitational wave signals.

1-OGC: The First Open Gravitational-wave Catalog of Binary Mergers from Analysis of Public Advanced LIGO Data

Abstract We present the first Open Gravitational-wave Catalog, obtained by using the public data from Advanced LIGO’s first observing run to search for compact-object binary mergers. Our analysis is based on new methods that improve the separation between signals and noise in matched-filter searches for gravitational waves from the merger of compact objects. The three most significant signals in our catalog correspond to the binary black hole mergers GW150914, GW151226, and LVT151012. We assume a common population of binary black holes for these three signals by defining a region of parameter space that is consistent with these events. Under this assumption, we find that LVT151012 has a 97.6% probability of being astrophysical in origin. No other significant binary black hole candidates are found, nor did we observe any significant binary neutron star or neutron star–black hole candidates. We make available our complete catalog of events, including the subthreshold population of candidates.

Investigating the noise residuals around the gravitational wave event GW150914

We use the Pearson cross-correlation statistic proposed by Liu and Jackson [1], and employed by Creswell et al. [2], to look for statistically significant correlations between the LIGO Hanford and Livingston detectors at the time of the binary black hole merger GW150914. We compute this statistic for the calibrated strain data released by LIGO, using both the residuals provided by LIGO and using our own subtraction of a maximum-likelihood waveform that is constructed to model binary black hole mergers in general relativity. To assign a significance to the values obtained, we calculate the cross-correlation of both simulated Gaussian noise and data from the LIGO detectors at times during which no detection of gravitational waves has been claimed. We find that after subtracting the maximum likelihood waveform there are no statistically significant correlations between the residuals of the two detectors at the time of GW150914.

New Eras in Physics

Dear readers, authors and reviewers of Annalen der Physik, On 16 November 2018, the 26th meeting of the General Conference on Weights and Measures in Versailles adopted a resolution on the revision of the International System of Units (SI).1 With this, the French metrology institution BIPM will give up its traditional role as host of the famous “Grand K”, the kilogram prototype, which is to be replaced by a fixed value of the Planck constant h.2 At the same time, also the elementary charge e,3 the Boltzmann constant k,4 and the Avogadro constant NA5 received new definitions so that in the future all seven SI units will be defined in terms of physical constants. These changes will come into effect on 20 May 2019, and on this occasion Annalen der Physik will publish a special issue “The Revised SI: Fundamental Constants, Basic Physics and Units”, edited by our Editorial Advisory Board member Klaus Blaum (Max Planck Institute for Nuclear Physics Heidelberg), Dmitry Budker (Johannes Gutenberg University of Mainz), Andrey Surzhykov (Technical University and Physikalisch-Technische Bundesanstalt – PTB, Braunschweig), and Joachim H. Ullrich (President of the PTB, the National Metrology Institute of Germany) (Figure 1). It is planned to contain Review Articles on the fundamental constants and corresponding units, as well as a substantial collection of further overview articles and new research results around these and the required high-precision measurements. Watch out for many articles to be already online at http://www.ann-phys.org (Early View)! This special issue will clearly be one of the AdP highlights in the New Year, as it is of fundamental importance for physics and the foundations of physical measurements. However, there are also other fields of physics that currently undergo revolutionary developments. One of them is certainly gravitational wave astronomy. We have already been glad to publish the article by the LIGO and VIRGO Collaborations on “The basic physics of the binary black hole merger GW150914” (the first detection in September 2014) which has been downloaded more than three times a day on average since. Now we are even happier to follow up with the Nobel Lectures 2017 “LIGO and the Discovery of Gravitational Waves”, Parts I to III, authored by the Laureates Rainer Weiss (article number 1800349), Barry C. Barish (article number 1800357), and Kip S. Thorne (article number 1800350) in the present issue. They are being accompanied by an Expert Opinion (article number 1800442) from our Board member Bruce Allen of the Max Planck Institute for Gravitational Physics Hannover and a Review Article on Forecasting Gamma-Ray Bursts with Gravitational Waves by Sarp Akcay (Friedrich-Schiller-Universität Jena and University College Dublin). The spectrum of recent top Review and Feature Articles in Annalen der Physik spreads further from astrophysical black holes over self-collimation in photonic crystals to Bose–Einstein condensation (article numbers 1700430, 1700049, and 1700124). And, last but not least, special issues will continue to be a cornerstone of the journal, with the 2017 article collection on Many-Body Localization having been cited almost 400 times already at present, also to be followed by ‘Physics of Information’ and ‘Advances in Physics of Semiconductors’ later this year. Suggestions for new special issue topics are always welcome at ann-phys@wiley.com. Generally, we have noticed increasing submission numbers as well as better-quality contributions, and we intend to keep up the standards of the journals by a strict editorial and peer-review selection process that currently results in an acceptance rate below 20%. Recent trends also include increasing submission numbers in applied physics fields as well as from China (more than one third of contributions in 2018), most notably in current topical areas such as quantum information or photonics. To support this significant development, we have appointed four new Editorial Advisory Board members in 2018, among them Qihuang Gong, Peking University; Hong-Bo Sun, Jilin University Changchun; Dingyu Xing, Nanjing University; and Pu Yu, Tsinghua University, Beijing, and with our colleague Huan Wang we have now an Editor working in the Wiley Beijing office. A warm welcome to each of you, and to all authors joining the growing AdP community! Wishing you a peaceful, healthy, successful and pleasant year 2019. Stefan Hildebrandt, Editor-in-Chief Nadezda Panarina, Maria E. Stournara, Huan Wang, James Cook, Matthew Lock, Editors

Calibration of the Advanced LIGO detectors for the discovery of the binary black-hole merger GW150914

In Advanced LIGO, detection and astrophysical source parameter estimation of the binary black hole merger GW150914 requires a calibrated estimate of the gravitational-wave strain sensed by the detectors. Producing an estimate from each detector's differential arm length control loop readout signals requires applying time domain filters, which are designed from a frequency domain model of the detector's gravitational-wave response. The gravitational-wave response model is determined by the detector's opto-mechanical response and the properties of its feedback control system. The measurements used to validate the model and characterize its uncertainty are derived primarily from a dedicated photon radiation pressure actuator, with cross-checks provided by optical and radio frequency references. We describe how the gravitational-wave readout signal is calibrated into equivalent gravitational-wave-induced strain and how the statistical uncertainties and systematic errors are assessed. Detector data collected over 38 calendar days, from September 12 to October 20, 2015, contain the event GW150914 and approximately 16 of coincident data used to estimate the event false alarm probability. The calibration uncertainty is less than 10% in magnitude and 10 degrees in phase across the relevant frequency band 20 Hz to 1 kHz.

ILLUMINATING BLACK HOLE BINARY FORMATION CHANNELS WITH SPINS IN ADVANCED LIGO

ABSTRACT The recent detections of the binary black hole mergers GW150914 and GW151226 have inaugurated the field of gravitational-wave astronomy. For the two main formation channels that have been proposed for these sources, isolated binary evolution in galactic fields and dynamical formation in dense star clusters, the predicted masses and merger rates overlap significantly, complicating any astrophysical claims that rely on measured masses alone. Here, we examine the distribution of spin–orbit misalignments expected for binaries from the field and from dense star clusters. Under standard assumptions for black hole natal kicks, we find that black hole binaries similar to GW150914 could be formed with significant spin–orbit misalignment only through dynamical processes. In particular, these heavy-black hole binaries can only form with a significant spin–orbit anti-alignment in the dynamical channel. Our results suggest that future detections of merging black hole binaries with measurable spins will allow us to identify the main formation channel for these systems.

The basic physics of the binary black hole merger GW150914

The first direct gravitational‐wave detection was made by the Advanced Laser Interferometer Gravitational Wave Observatory on September 14, 2015. The GW150914 signal was strong enough to be apparent, without using any waveform model, in the filtered detector strain data. Here, features of the signal visible in the data are analyzed using concepts from Newtonian physics and general relativity, accessible to anyone with a general physics background. The simple analysis presented here is consistent with the fully general‐relativistic analyses published elsewhere, in showing that the signal was produced by the inspiral and subsequent merger of two black holes. The black holes were each of approximately , still orbited each other as close as ∼350 km apart and subsequently merged to form a single black hole. Similar reasoning, directly from the data, is used to roughly estimate how far these black holes were from the Earth, and the energy that they radiated in gravitational waves.

Metallicity-constrained merger rates of binary black holes and the stochastic gravitational wave background

The recent detection of the binary black hole merger GW150914 demonstrates the existence of black holes more massive than previously observed in X-ray binaries in our Galaxy. This article explores different scenarios of black hole formation in the context of self-consistent cosmic chemical evolution models that simultaneously match observations of the cosmic star formation rate, optical depth to reionization and metallicity of the interstellar medium. This framework is used to calculate the mass distribution of merging black hole binaries and its evolution with redshift. We also study the implications of the black hole mass distribution for the stochastic gravitational wave background from mergers and from core collapse events.

Properties of the Binary Black Hole Merger GW150914.

On September 14, 2015, the Laser Interferometer Gravitational-Wave Observatory (LIGO) detected a gravitational-wave transient (GW150914); we characterize the properties of the source and its parameters. The data around the time of the event were analyzed coherently across the LIGO network using a suite of accurate waveform models that describe gravitational waves from a compact binary system in general relativity. GW150914 was produced by a nearly equal mass binary black hole of masses 36_{-4}^{+5}M_{⊙} and 29_{-4}^{+4}M_{⊙}; for each parameter we report the median value and the range of the 90% credible interval. The dimensionless spin magnitude of the more massive black hole is bound to be <0.7 (at 90% probability). The luminosity distance to the source is 410_{-180}^{+160} Mpc, corresponding to a redshift 0.09_{-0.04}^{+0.03} assuming standard cosmology. The source location is constrained to an annulus section of 610 deg^{2}, primarily in the southern hemisphere. The binary merges into a black hole of mass 62_{-4}^{+4}M_{⊙} and spin 0.67_{-0.07}^{+0.05}. This black hole is significantly more massive than any other inferred from electromagnetic observations in the stellar-mass regime.

GW150914: First results from the search for binary black hole coalescence with Advanced LIGO

On September 14, 2015 at 09:50:45 UTC the two detectors of the Laser Interferometer Gravitational-wave Observatory (LIGO) simultaneously observed the binary black hole merger GW150914. We report the results of a matched-filter search using relativistic models of compact-object binaries that recovered GW150914 as the most significant event during the coincident observations between the two LIGO detectors from September 12 to October 20, 2015. GW150914 was observed with a matched filter signal-to-noise ratio of 24 and a false alarm rate estimated to be less than 1 event per 203000 years, equivalent to a significance greater than 5.1 σ.

ASTROPHYSICAL IMPLICATIONS OF THE BINARY BLACK HOLE MERGER GW150914

ABSTRACT The discovery of the gravitational-wave (GW) source GW150914 with the Advanced LIGO detectors provides the first observational evidence for the existence of binary black hole (BH) systems that inspiral and merge within the age of the universe. Such BH mergers have been predicted in two main types of formation models, involving isolated binaries in galactic fields or dynamical interactions in young and old dense stellar environments. The measured masses robustly demonstrate that relatively “heavy” BHs ( ) can form in nature. This discovery implies relatively weak massive-star winds and thus the formation of GW150914 in an environment with a metallicity lower than about 1/2 of the solar value. The rate of binary-BH (BBH) mergers inferred from the observation of GW150914 is consistent with the higher end of rate predictions ( Gpc−3 yr−1) from both types of formation models. The low measured redshift ( ) of GW150914 and the low inferred metallicity of the stellar progenitor imply either BBH formation in a low-mass galaxy in the local universe and a prompt merger, or formation at high redshift with a time delay between formation and merger of several Gyr. This discovery motivates further studies of binary-BH formation astrophysics. It also has implications for future detections and studies by Advanced LIGO and Advanced Virgo, and GW detectors in space.