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A Gravitational-Wave Transient Catalog of Compact Binary Mergers Observed by LIGO and Virgo During the First and Second Observing Runs

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A Gravitational-Wave Transient Catalog of Compact Binary Mergers Observed by LIGO and Virgo During the First and Second Observing Runs GWTC-1: A Gravitational-Wave Transient Catalog of Compact Binary Mergers Observed by LIGO and Virgo during the First and Second Observing Runs The LIGO Scientific Collaboration and The Virgo Collaboration (Compiled: 30 November 2018) We present the results from three gravitational-wave searches for coalescing compact binaries with component masses above 1M during the first and second observing runs of the Advanced gravitational-wave detector network. During the first observing run (O1), from September 12th, 2015 to January 19th, 2016, gravitational waves from three binary black hole mergers were detected. The second observing run (O2), which ran from November 30th, 2016 to August 25th, 2017, saw the first detection of gravitational waves from a binary neutron star inspiral, in addition to the observation of gravitational waves from a total of seven binary black hole mergers, four of which we report here for the first time: GW170729, GW170809, GW170818 and GW170823. For all significant gravitational-wave events, we provide estimates of the source properties. The detected binary black +3:1 +15:6 +120 holes have total masses between 18:6−0:7M and 85:1−10:9M , and range in distance between 320−110 Mpc +1350 and 2750−1320 Mpc. No neutron star – black hole mergers were detected. In addition to highly significant gravitational-wave events, we also provide a list of marginal event candidates with an estimated false alarm rate less than 1 per 30 days. From these results over the first two observing runs, which include approximately one gravitational-wave detection per 15 days of data searched, we infer merger rates at the 90% confidence intervals of 110−3840 Gpc−3 y−1 for binary neutron stars and 9:7−101 Gpc−3 y−1 for binary black holes, and determine a neutron star – black hole merger rate 90% upper limit of 610 Gpc−3 y−1. PACS numbers: 04.80.Nn, 04.25.dg, 95.85.Sz, 97.80.-d 04.30.Db, 04.30.Tv I. INTRODUCTION use waveform models to compare against the data, but instead identifies regions of excess power in the time-frequency rep- resentation of the gravitational strain. We report results from The first observing run (O1) of Advanced LIGO, which a cWB analysis that is optimized for the detection of compact took place from September 12th, 2015 until January 19th, 2016 binaries with a total mass less than 100M . A different tuning saw the first detections of gravitational waves (GWs) from of the cWB analysis is used for a search for intermediate-mass stellar-mass binary black holes (BBHs) [1–4]. After an up- BBHs with total masses greater than 100M ; the results of grade and commissioning period, the second observing run that analysis are discussed elsewhere. The three searches re- (O2) of the Advanced LIGO detectors [5] commenced on ported here use different methodologies to identify GWs from November 30th, 2016, and ended on August 25th, 2017. On compact binaries in an overlapping but not identical search August 1st, 2017 the Advanced Virgo detector [6] joined the space, thus providing three largely independent analyses that observing run, enabling the first three-detector observations of allow for important crosschecks and yield consistent results. GWs. This network of ground-based interferometric detectors All searches have undergone improvements since O1, making is sensitive to GWs from the inspiral, merger and ringdown of it scientifically valuable to reanalyze the O1 data in order to compact binary coalescences (CBCs), covering a frequency reevaluate the significance of previously identified GW events range from about 15 Hz up to a few kHz (see Fig.1). In this and to potentially discover new ones. catalog, we report eleven confident detections of GWs from The searches identified a total of ten BBH mergers compact binary mergers as well as a selection of less signifi- and one binary neutron star (BNS) signal. The GW cant triggers from both observing runs. The observations re- events GW150914, GW151012,1 GW151226, GW170104, ported here and future GW detections will shed light on binary GW170608, GW170814 and GW170817 have been reported formation channels, enable precision tests of general relativ- previously [4, 14–17]. In this catalog, we announce four ity (GR) in its strong-field regime, and open up new avenues previously unpublished BBH mergers observed during O2: of astronomy research. GW170729, GW170809, GW170818 and GW170823. We es- The events presented here are obtained from two matched- +15:6 timate the total mass of GW170729 to be 85:1−10:9 M , mak- filter searches, PyCBC[7,8] and GstLAL[9, 10], using rela- ing it the highest-mass BBH observed to date. GW170818 is tivistic models of GWs from CBCs, as well as an unmodeled the second BBH observed in triple-coincidence between the search for short-duration transient signals or bursts, coherent two LIGO observatories and Virgo after GW170814 [15]. As WaveBurst (cWB) [11]. The two matched-filter searches tar- the sky location is primarily determined by the differences get GWs from compact binaries with a redshifted total mass M(1 + z) of 2-500M for PyCBC and 2-400M for Gst- LAL, where z is the cosmological redshift of the source bi- nary [12], and with maximal dimensionless spins of 0.998 for 1 The event GW151012 was previously referred to as LVT151012. Here, we black holes (BHs) and 0.05 for neutron stars (NSs). The re- retire the LVT nomenclature; all candidate events with an estimated false sults of a matched-filter search for sub-solar mass compact alarm rate (FAR) less than 1 per 30 days and a probability > 0:5 of being of objects in O1 can be found in Ref. [13]; the results for O2 astrophysical origin (see Eq. (10) for the definition) are henceforth denoted will be discussed elsewhere. The burst search, cWB, does not with the GW prefix. All other candidates are referred to as marginal. 2 in the times of arrival of the GW signal at the different de- II. INSTRUMENTAL OVERVIEW AND DATA tector sites, LIGO-Virgo coincident events have a vastly im- proved sky localization, which is crucial for electromagnetic A. LIGO Instruments follow-up campaigns [18–21]. The reanalysis of the O1 data did not result in the discovery of any new GW events, but The Advanced LIGO detectors [57, 58] began scientific GW151012 is now detected with increased significance. In operations in September 2015 and almost immediately de- addition, we list 14 GW candidate events that have an esti- tected the first gravitational waves from the BBH merger mated false alarm rate (FAR) less than 1 per 30 days in ei- GW150914. ther of the two matched-filter analyses but whose astrophysi- Between O1 and O2 improvements were made to both cal origin cannot be established nor excluded unambiguously LIGO instruments. At LIGO-Livingston (LLO) a malfunc- (Sec. VII). tioning temperature sensor [59] was replaced immediately af- ter O1 contributing to an increase in BNS range from ∼60 Gravitational waves from compact binaries carry informa- Mpc to ∼80 Mpc.2 Other major changes included adding pas- tion about the properties of the source such as the masses and sive tuned mass dampers on the end test mass suspensions to spins. These can be extracted via Bayesian inference by using reduce ringing up of mechanical modes, installing a new out- theoretical models of the GW signal that describe the inspiral, put Faraday isolator, adding a new in-vacuum array of pho- merger and ringdown of the final object for BBH [22–29], and todiodes for stabilizing the laser intensity, installing higher the inspiral (and merger) for BNS [30–32]. Such models are quantum-efficiency photo-diodes at the output port, and re- built by combining post-Newtonian calculations [33–37], the placing the compensation plate on the input test mass suspen- effective-one-body formalism [38–43] and numerical relativ- sion for the Y-arm. An attempt to upgrade the LLO laser ity [44–49]. Based on a variety of theoretical models, we pro- to provide higher input power was not successful. During vide key source properties of all confident GW detections. For O2, improvements to the detector sensitivity continued and previously reported detections, we provide updated parameter sources of scattered light noise were mitigated. As a result the estimates which exploit refined instrumental calibration, data sensitivity of the LLO instrument rose from a BNS range of cleaning (for O2 data) [50, 51] and updated amplitude power 80 Mpc at the beginning of O2 to greater than 100 Mpc by spectral density estimates [52, 53]. run’s end. The observation of these GW events allows us to place con- The LIGO-Hanford (LHO) detector had a range of ∼80 straints on the rates of stellar-mass BBH and BNS mergers Mpc as O1 ended, and it was decided to concentrate on in- in the Universe and probe their mass and spin distributions, creasing the input laser power and forgo any incursions into putting them into astrophysical context. The non-observation the vacuum system. Increasing the input laser power to 50 W of GWs from a neutron star–black hole binary (NSBH) yields was successful, but since this did not result in an increase in a stronger 90% upper limit on the rate. The details of the as- sensitivity, the LHO detector operated with 30 W input power trophysical implications of our observations are discussed in during O2. It was eventually discovered that there was a point Ref. [54]. absorber on one of the input test mass optics which we spec- ulate led to increased coupling of input “jitter” noise from the This paper is organised as follows: In Sec.II we provide laser table into the interferometer.
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