GWTC-1: A Gravitational-Wave Transient Catalog of Compact Binary Mergers Observed by LIGO and Virgo during the First and Second Observing Runs

TL;DR

GWTC-1 compiles the first two LIGO-Virgo observing runs into a unified catalog of 11 confident compact-binary-merger events (10 BBH, 1 BNS) plus marginal candidates, using three independent pipelines (PyCBC, GstLAL, cWB). The study leverages reanalyzed O1 data and recalibrated O2 data to improve event significances, refine source-property inferences, and constrain merger-rate densities across BBH, BNS, and NSBH populations; GW170817 provides stringent tidal-deformability bounds. The analysis demonstrates that higher-order waveform harmonics are not essential for the current measurements, while multi-detector networks significantly improve sky localization, enabling EM follow-ups. Collectively, GWTC-1 delivers updated population insights, tests of GR in the strong-field regime, and a robust foundation for upcoming observing runs (O3+).

Abstract

We present the results from three gravitational-wave searches for coalescing compact binaries with component masses above 1$\mathrm{M}_\odot$ during the first and second observing runs of the Advanced gravitational-wave detector network. During the first observing run (O1), from September $12^\mathrm{th}$, 2015 to January $19^\mathrm{th}$, 2016, gravitational waves from three binary black hole mergers were detected. The second observing run (O2), which ran from November $30^\mathrm{th}$, 2016 to August $25^\mathrm{th}$, 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 holes have total masses between $18.6_{-0.7}^{+3.2}\mathrm{M}_\odot$, and $84.4_{-11.1}^{+15.8} \mathrm{M}_\odot$, and range in distance between $320_{-110}^{+120}$ Mpc and $2840_{-1360}^{+1400}$ 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 $110\, -\, 3840$ $\mathrm{Gpc}^{-3}\,\mathrm{y}^{-1}$ for binary neutron stars and $9.7\, -\, 101$ $\mathrm{Gpc}^{-3}\,\mathrm{y}^{-1}$ for binary black holes assuming fixed population distributions, and determine a neutron star - black hole merger rate 90% upper limit of $610$ $\mathrm{Gpc}^{-3}\,\mathrm{y}^{-1}$.

Figures (17)

• Figure 1: Left: BNS range for each instrument during$O 2$. The break at week 3 is for the 2016 end-of-year holidays. There is an additional break in the run at week 23 to make improvements to instrument sensitivity. The Montana earthquake's impact on the LHO instrument sensitivity can be seen at week 31 . Virgo joins $O 2$ in week 34 . Right: Amplitude spectral density of the total strain noise of the Virgo, LHO, and LLO detectors. The curves are representative of the best performance of each detector during $O 2$.
• Figure 2: Cumulative histograms of search results for the matched-filter searches, plotted versus inverse false-alarm rate. The dashed lines show the expected background, given the analysis time. Shaded regions denote sigma uncertainty bounds for Poisson uncertainty. The blue dots are the named gravitational-wave events found by each respective search. Any events with a measured or bounded inverse false-alarm rate greater than 3000 y are shown with an arrow pointing right. Left: PyCBC results. Right: GstLAL results.
• Figure 3: Cumulative histograms of search results for the cWB search, plotted versus the inverse false-alarm rate. The dashed lines show the expected background, given the analysis time. Shaded regions denote sigma uncertainty bounds for Poisson uncertainty. The blue dots are the named gravitational-wave events found by each respective search. Any events with a measured or bounded inverse false-alarm rate greater than 3000 y are shown with an arrow pointing right.
• Figure 4: Parameter estimation summary plots I. Posterior probability densities of the component masses and final masses and spins of the GW events. For the two-dimensional distributions, the contours show$90 \%$ credible regions. Left: Source-frame component masses $m_{1}$ and $m_{2}$. We use the convention that $m_{1} \geq m_{2}$, which produces the sharp cut in the two-dimensional distribution. Lines of constant mass ratio $q=m_{2} / m_{1}$ are shown for $1 / q=2,4,8$. For low-mass events, the contours follow lines of constant chirp mass. Right: The mass $M_{f}$ and dimensionless spin magnitude $a_{f}$ of the final black holes. The colored event labels are ordered by source-frame chirp mass. The same color code and ordering (where appropriate) apply to Figs. 5-8.
• Figure 5: Parameter estimation summary plots II. Posterior probability densities of the mass ratio and spin parameters of the GW events. The shaded probability distributions have equal maximum widths, and horizontal lines indicate the medians and$90 \%$ credible intervals of the distributions. For the two-dimensional distributions, the contours show $90 \%$ credible regions. Events are ordered by source-frame chirp mass. The colors correspond to the colors used in summary plots. For GW170817, we show results for the high-spin prior $a_{i}<0.89$. Top left: The mass ratio $q=m_{2} / m_{1}$. Top right: The effective aligned spin magnitude $\chi_{\text{eff }}$. Bottom left: Contours of $90 \%$ credible regions for the effective aligned spin and mass ratio of the binary components for low- (high-) mass binaries are shown in the upper (lower) panel. Bottom right: The effective precession spin posterior (colored) and its effective prior distribution (white) for BBH (BNS) events. The priors are conditioned on the $\chi_{\text{eff }}$ posterior distributions.