Search

We present the fourth Open Gravitational-wave Catalog (4-OGC) of binary neutron star (BNS), binary black hole (BBH), and neutron star–black hole (NSBH) mergers. The catalog includes observations from 2015 to 2020 covering the first through third observing runs (O1, O2, O3a, and O3b) of Advanced LIGO and Advanced Virgo. The updated catalog includes seven BBH mergers that were not previously reported with high significance during O3b for a total of 94 observations: 90 BBHs, 2 NSBHs, and 2 BNSs. The most confident new detection, GW200318_191337, has component masses 49.1 − 12.0 + 16.4 M ⊙ and 31.6 − 11.6 + 12.0 M ⊙ ; its redshift of 0.84 − 0.35 + 0.4 (90% credible interval) may make it the most distant merger so far. We estimate the merger rate of BBH sources, assuming a power-law mass distribution containing an additive Gaussian peak, to be 16.5 − 6.2 + 10.4 (25.0 − 8.0 + 12.6) Gpc−3 yr−1 at a redshift of z = 0 (0.2). For BNS and NSBH sources, we estimate a merger rate of 200 − 148 + 309 Gpc−3 yr−1 and 19 − 14 + 30 Gpc−3 yr−1, respectively, assuming the known sources are representative of the total population. We provide reference parameter estimates for each of these sources using an up-to-date model accounting for instrumental calibration uncertainty. The corresponding data release also includes our full set of subthreshold candidates. [ABSTRACT FROM AUTHOR]

We present a search for gravitational waves from subsolar mass compact-binary mergers that allows for nonnegligible orbital eccentricity. Subsolar mass black holes are a signature of primordial origin black holes, which may be a component of dark matter. To produce binary coalescences, primordial black holes may form close binaries either in the early universe or more recently through dynamical interactions. A signature of dynamical formation would be the observation of noncircularized orbits. We search for black hole mergers where the primary mass is 0.1–7M⊙ and the secondary mass is 0.1–1M⊙. We allow for eccentricity up to ∼0.3 at a dominant-mode gravitational-wave frequency of 10 Hz for binaries with component masses >0.5M⊙. We find no convincing candidates in the public LIGO data from 2015–2017. The two most promising candidates have a false alarm rate of 1 per 3 and 4 yr, respectively, which combined is only a ∼2.4σ deviation from the expected Poisson rate. Given the marginal statistical significance, we place upper limits on the rate of subsolar mass mergers under the assumption of a null observation and compare how these limits may inform the possible dark matter contribution. [ABSTRACT FROM AUTHOR]

Due to their small mass, subsolar mass black hole binaries would have to be primordial in origin instead of the result of stellar evolution. Soon after formation in the early universe, primordial black holes can form binaries after decoupling from the cosmic expansion. Alternatively, primordial black holes as dark matter could also form binaries in the late universe due to dynamical encounters and gravitational-wave braking. A significant feature for this channel is the possibility that some sources retain nonzero eccentricity in the LIGO/Virgo band. Assuming all dark matter is primordial black holes with a delta function mass distribution, 1M⊙–1M⊙ binaries formed in this late-universe channel can be detected by Advanced LIGO and Virgo with their design sensitivities at a rate of yr−1, where 12%(3%) of events have eccentricity at a gravitational-wave frequency of 10 Hz, e10 Hz ≥ 0.01(0.1), and nondetection can constrain the binary formation rate within this model. Third generation detectors would be expected to detect subsolar mass eccentric binaries as light as 0.01M⊙ within this channel, if they accounted for the majority of the dark matter. Furthermore, we use simulated gravitational-wave data to study the ability to search for eccentric gravitational-wave signals using a quasi-circular waveform template bank with Advanced LIGO design sensitivity. For a match-filtering targeted search, assuming binaries with a delta function mass of 0.1(1)M⊙ and the eccentricity distribution derived from this late-universe formation channel, 41%(6%) of the signals would be missed compared to the ideal detection rate due to the mismatch in the gravitational-wave signal from eccentricity. [ABSTRACT FROM AUTHOR]

Einstein's general relativity, as the most successful theory of gravity, is one of the cornerstones of modern physics. However, the experimental tests for gravity in the high energy region are limited. The emerging gravitational-wave astronomy has opened an avenue for probing the fundamental properties of gravity in a strong and dynamical field, and in particular, a high energy regime. In this work, we test the parity conservation of gravity with gravitational waves. If the parity symmetry is broken, the left- and right-handed modes of gravitational waves would follow different equations of motion, dubbed as birefringence. We perform full Bayesian inference by comparing the state-of-the-art waveform with parity violation with the compact binary coalescence data released by LIGO and Virgo collaboration. We do not find any violations of general relativity, thus constrain the lower bound of the parity-violating energy scale to be 0.09 GeV through the velocity birefringence of gravitational waves. This provides the most stringent experimental test of gravitational parity symmetry to date. We also find third generation gravitational-wave detectors can enhance this bound to GeV if there is still no violation, comparable to the current energy scale in particle physics, which indicates gravitational-wave astronomy can usher in a new era of testing the ultraviolet behavior of gravity in the high energy region. [ABSTRACT FROM AUTHOR]

The variation mechanism of blazars is a long-standing open question. Observations of polarization can provide us with more information to constrain models. In this work, we collect long-term multiwavelength data on AO 0235+164, and analyse the correlations between them by using the local cross-correlation function. We find that both γ-ray and the optical V-band light curves are correlated with the radio light curve beyond the 3σ significance level. The regions emitting the γ-ray and optical radiation coincide within errors, and are located pc upstream of the core region of 15 GHz, which is beyond the broad-line region. The color index shows the redder-when-brighter trend in the low flux state, but turns to the bluer-when-brighter trend in the high flux state, while the γ-ray spectral index always shows the softer-when-brighter trend. We propose that such complex variation trends can be explained by the increasing jet component with two constant components. The optical polarization degree (PD) flares and optical flux flares are not synchronous. It seems that one flux peak is sandwiched by two PD peaks, which have inverse rotation trajectories in the qu plane. The helical jet model can schematically show these characteristics of polarization with fine-tuned parameters. The change in viewing angle is suggested to be the primary variable that leads to all these variations, although other possibilities such as the shock-in-jet model or the hadronic model are not excluded completely. [ABSTRACT FROM AUTHOR]