Einstein's theory of general relativity predicts that gravitational waves (GWs) are tensor-polarized, with two modes of polarization: plus ($h_+$) and cross ($h_\times$). The unmodeled GW burst analysis pipeline, \textit{BayesWave}, offers two tensor-polarized signal models: the elliptical polarization model ($E$) and the relaxed polarization model ($R$). Future expansion of the global GW detector network will enable more accurate studies of GW polarizations with GW bursts. Here a multi-detector analysis is conducted to compare the performance of $E$ and $R$ in characterizing elliptical and nonelliptical GW polarizations, using nonprecessing and precessing binary black holes (BBHs) respectively as representative synthetic sources. It is found that both models reconstruct the elliptical nonprecessing BBH signals accurately, but $E$ has a higher Bayesian evidence than $R$ as it is has fewer model parameters. The same is true for precessing BBHs that are reconstructed equally well by both models. However, for some events with high precession and especially with three or more detectors, the reconstruction accuracy and evidence of $R$ surpass $E$. The analysis is repeated for BBH events from the third LIGO-Virgo-KAGRA observing run, and the results show that $E$ is preferred over $R$ for existing detections. Although $E$ is generally preferred for its simplicity, it insists on elliptical polarizations, whereas $R$ can measure generic GW polarization content in terms of Stokes parameters. The accuracy of $R$ in recovering polarization content improves as the detector network expands, and the performance is independent of the GW signal morphology.
A central challenge in Gravitational Wave Astronomy is identifying weak signals in the presence of non-stationary and non-Gaussian noise. The separation of gravitational wave signals from noise requires good models for both. When accurate signal models are available, such as for binary Neutron star systems, it is possible to make robust detection statements even when the noise is poorly understood. In contrast, searches for "un-modeled" transient signals are strongly impacted by the methods used to characterize the noise. Here we take a Bayesian approach and introduce a multi-component, variab…
The global gravitational-wave detector network achieves higher detection rates, better parameter estimates, and more accurate sky localisation, as the number of detectors, $\mathcal{I}$ increases. This paper quantifies network performance as a function of $\mathcal{I}$ for BayesWave, a source-agnostic, wavelet-based, Bayesian algorithm which distinguishes between true astrophysical signals and instrumental glitches. Detection confidence is quantified using the signal-to-glitch Bayes factor, $\mathcal{B}_{\mathcal{S},\mathcal{G}}$. An analytic scaling is derived for $\mathcal{B}_{\mathcal{S},\m…
We describe updates and improvements to the BayesWave gravitational wave transient analysis pipeline, and provide examples of how the algorithm is used to analyze data from ground-based gravitational wave detectors. BayesWave models gravitational wave signals in a morphology-independent manner through a sum of frame functions, such as Morlet-Gabor wavelets or chirplets. BayesWave models the instrument noise using a combination of a parametrized Gaussian noise component and non-stationary and non-Gaussian noise transients. Both the signal model and noise model employ trans-dimensional sampling,…
With the advanced LIGO and Virgo detectors taking observations the detection of gravitational waves is expected within the next few years. Extracting astrophysical information from gravitational wave detections is a well-posed problem and thoroughly studied when detailed models for the waveforms are available. However, one motivation for the field of gravitational wave astronomy is the potential for new discoveries. Recognizing and characterizing unanticipated signals requires data analysis techniques which do not depend on theoretical predictions for the gravitational waveform. Past searches …
The LIGO-Virgo collaboration uses a variety of techniques to detect and characterize gravitational waves. One approach is to use templates - models for the signals derived from Einstein's equations. Another approach is to extract the signals directly from the coherent response of the detectors in LIGO-Virgo network. Both approaches played an important role in the first gravitational wave detections. Here we extend the BayesWave analysis algorithm, which reconstructs gravitational wave signals using a collection of continuous wavelets, to use a generalized wavelet family, known as chirplets, th…
We investigate the detectability of massive mode of polarization of Gravitational Waves (GWs) in f(R) theory of gravity associated with Gamma Ray Bursts (GRBs) sources. We obtain the beam pattern function of Laser Interferometric Gravitational wave Observatory (LIGO) corresponding to the massive polarization of GWs and perform Bayesian analysis to study this polarization. It is found that the massive polarization component with a mass of 10^-22eV/c2 is too weak to be detected at LIGO with its current configuration.
We report polarization measurements in two prompt emissions of gamma-ray bursts, GRB 110301A and GRB 110721A, observed with the Gamma-ray burst polarimeter (GAP) aboard IKAROS solar sail mission. We detected linear polarization signals from each burst with polarization degree of $Π= 70 \pm 22$% with statistical significance of $3.7 σ$ for GRB 110301A, and $Π= 84^{+16}_{-28}$% with $3.3 σ$ confidence level for GRB 110721A. We did not detect any significant change of polarization angle. These two events had shorter durations and dimmer brightness compared with GRB 100826A, which showed a signifi…
Gamma-ray bursts and their afterglows are thought to be produced by an ultra-relativistic jet. One of the most important open questions is the outflow composition: the energy may be carried out from the central source either as kinetic energy (of baryons and/or pairs), or in electromagnetic form (Poynting flux). While the total observable flux may be indistinguishable in both cases, its polarization properties are expected to differ markedly. The prompt emission and afterglow polarization are also a powerful diagnostic of the jet geometry. Again, with subtle and hardly detectable differences i…
We report the strictest observational verification of CPT invariance in the photon sector, as a result of gamma-ray polarization measurement of distant gamma-ray bursts (GRBs), which are brightest stellar-size explosions in the universe. We detected the gamma-ray polarization of three GRBs with high significance, and the source distances may be constrained by a well-known luminosity indicator for GRBs. For the Lorentz- and CPT-violating dispersion relation E_{\pm}^2=p^2 \pm 2ξp^3/M_{Pl}, where \pm denotes different circular polarization states of the photon, the parameter ξis constrained as |ξ…
Lorentz invariance violations (LIV) can yield vacuum birefringence, which results in an energy-dependent rotation of the polarization vector of linearly polarized emission from astrophysical sources. It is believed that if the relative rotation angle ($ΔΘ$) of the polarization vector of high energy photons with respect to that of low energy photons is larger than $π/2$, then the net polarization of the signal would be significantly depleted and could not be as high as the observed level. Hence, the measurement of high polarization implies that $ΔΘ$ should not be too large. In this work, we ass…
Significant gravitational wave emission is expected from gamma-ray bursts arising from compact stellar mergers, and possibly also from bursts associated with fast-rotating massive stellar core collapses. These models have in common a high angular rotation rate, and observations provide evidence for jet collimation of the photon emission, with properties depending on the polar angle, which may also be of relevance for X-ray flashes. Here we consider the gravitational wave emission and its polarization as a function of angle which is expected from such sources. We discuss possible correlations b…
A possible birefringence effect that arises in quantum gravity leads to a frequency-dependent rotation of the polarization angle of linearly polarized emission from distant sources. Here we use the UV/optical polarization data of the afterglows of GRB 020813 and GRB 021004 to constrain this effect. We find an upper limit on the Gambini & Pulin birefringence parameter $| η| <2\times 10^{-7}$. This limit is of 3 orders better than the previous limits from observations of AGNs and of the Crab pulsar. Much stronger limits may be obtained by the future observation of polarization of the prompt $γ$-…
The Einstein's equivalence principle can be tested by using parameterized post-Newtonian parameters, of which the parameter $γ$ has been constrained by comparing the arrival times of photons with different energies. It has been constrained by a variety of astronomical transient events, such as gamma-ray bursts (GRBs), fast radio bursts as well as pulses of pulsars, with the most stringent constraint of $Δγ\lesssim 10^{-15}$. In this letter, we consider the arrival times of lights with different circular polarization. For a linearly polarized light, it is the combination of two circularly polar…
Constraints on possible Lorentz invariance violation (LIV) to first order in $E/M_{\rm Planck}$ for photons in the framework of effective field theory (EFT) are discussed, taking cosmological factors into account. Then, using the reported detection of polarized soft $γ$-ray emission from the $γ$-ray burst GRB041219a that is indicative of an absence of vacuum birefringence, together with a very recent improved method for estimating the redshift of the burst, we derive constraints on the dimension 5 Lorentz violating modification to the Lagrangian of an effective local QFT for QED. Our new const…
If the weak equivalence principle (WEP) is broken, the measured values of the parametrized post-Newtonian parameter $γ$ from photons with left- and right-handed circular polarizations should differ slightly, leading to the arrival-time difference of these two circular components. Thus, the polarization vector of a linearly polarized light may rotate during the propagation. The rotation angle of the polarization vector depends on both the photon energy and the distance of the source. It is believed that if the rotation angle differs by more than $π/2$ over an energy range, then the net polariza…
We present a unified general formalism for ultraviolet Lorentz invariance violation (LV) testing through electromagnetic wave propagation, based on both dispersion and rotation measure data. This allows for a direct comparison of the efficacy of different data to constrain LV. As an example we study the signature of LV on the rotation of the polarization plane of $γ$-rays from gamma ray bursts in a LV model. Here $γ$-ray polarization data can provide a strong constraint on LV, 13 orders of magnitude more restrictive than a potential constraint from the rotation of the cosmic microwave backgrou…
We show that the recent measurements of linear polarization in gamma rays from GRB 930131 and GRB 960924 constrain certain types of relativity violations in photons to less than parts in 10^{37}, representing an improvement in sensitivity by a factor of 100,000.
