Om S. Salafia, Gabriele Ghisellini, Giancarlo Ghirlanda, Monica Colpi

We show that GRB170817A and the subsequent radio and X-ray observations can be interpreted as due to an isotropic fireball loaded with a small amount ($M\sim 3\times 10^{-6}\,{\rm M_\odot}$) of neutron-rich ($Y_{\rm e}\sim 0.06$) material, which expands relativistically reaching a Lorentz factor $\Gamma\sim 5$. The physical picture resembles that of a giant flare from a magnetar, and could have been driven by an ultra-strong magnetic field $B\sim 3\times 10^{16}\,{\rm G}$ produced through amplification by magnetohydrodynamic turbulence at the beginning of the merger phase of the progenitor double neutron-star binary. Within such picture, the X-ray and radio data indicate a very tenuous ($n\sim 10^{-5}\,{\rm cm^{-3}}$) circum-binary medium, suggesting that the binary was outside the host galaxy in our direction, or that some process has blown a cavity around the binary before the merger. No relativistic jet is needed to explain the observations published in the literature so far, but we show that future radio and X-ray observations can be used to rule out the proposed picture. If our interpretation turns out to be correct, it indicates that not all double neutron-star mergers produce a jet, while most should feature this isotropic, hard X-ray component that can be a powerful guide to the discovery of additional kilonovae associated to relatively nearby gravitational wave events.

Daniel George, E. A. Huerta

The recent Nobel-prize-winning detections of gravitational waves from merging black holes and the subsequent detection of the collision of two neutron stars in coincidence with electromagnetic observations have inaugurated a new era of multimessenger astrophysics. To enhance the scope of this emergent field of science, we pioneered the use of deep learning with convolutional neural networks, that take time-series inputs, for rapid detection and characterization of gravitational wave signals. This approach, Deep Filtering, was initially demonstrated using simulated LIGO noise. In this article, we present the extension of Deep Filtering using real data from LIGO, for both detection and parameter estimation of gravitational waves from binary black hole mergers using continuous data streams from multiple LIGO detectors. We demonstrate for the first time that machine learning can detect and estimate the true parameters of real events observed by LIGO. Our results show that Deep Filtering achieves similar sensitivities and lower errors compared to matched-filtering while being far more computationally efficient and more resilient to glitches, allowing real-time processing of weak time-series signals in non-stationary non-Gaussian noise with minimal resources, and also enables the detection of new classes of gravitational wave sources that may go unnoticed with existing detection algorithms. This unified framework for data analysis is ideally suited to enable coincident detection campaigns of gravitational waves and their multimessenger counterparts in real-time.

Rafael Bravo, Sander Mooij, Gonzalo A. Palma, Bastián Pradenas

We show that a perturbed inflationary spacetime, driven by a canonical single scalar field, is invariant under a special class of coordinate transformations together with a field reparametrization of the curvature perturbation in co-moving gauge. This transformation may be used to derive the squeezed limit of the 3-point correlation function of the co-moving curvature perturbations valid in the case that these do not freeze after horizon crossing. This leads to a generalized version of Maldacena's non-Gaussian consistency relation in the sense that the bispectrum squeezed limit is completely determined by spacetime diffeomorphisms. Just as in the case of the standard consistency relation, this result may be understood as the consequence of how long-wavelength modes modulate those of shorter wavelengths. This relation allows one to derive the well known violation to the consistency relation encountered in ultra slow-roll, where curvature perturbations grow exponentially after horizon crossing.

Shao-Long Chen, Zhaofeng Kang

The absence of any confirmative signals from extensive DM searching motivates us to go beyond the conventional WIMPs scenario. The feebly interacting massive particles (FIMPs) paradigm provides a good alternative which, despite of its feebly interaction with the thermal particles, still could correctly produce relic abundance without conventional DM signals. The Infrared-FIMP based on the renormalizable operators is usually suffering the very tiny coupling drawback, which can be overcome in the UltraViolet-FIMP scenario based on high dimensional effective operators. However, it is sensitive to the history of the very early Universe. The previous works terminates this sensitivity at the reheating temperature $T_{RH}$. We, motivated by its UV-sensitivity, investigate the effects from the even earlier Universe, reheating era. We find that in the usual case with $T_{RH}\gg m_{\rm DM}$, the production rate during reheating is very small as long as the effective operators dimension $d \leq 8$. Besides, we consider the contribution from the mediator, which may be produced during reheating. Moreover, we study the situation when $T_{RH}$ is even lower than $m_{\rm DM}$ and DM can be directly produced during reheating if its mass does not exceed $T_{MAX}$.

Eemeli Annala, Tyler Gorda, Aleksi Kurkela, Aleksi Vuorinen

The LIGO/Virgo detection of gravitational waves originating from a neutron-star merger, GW170817, has recently provided new stringent limits on the tidal deformabilities of the stars involved in the collision. Combining this measurement with the existence of two-solar-mass stars, we generate the most generic family of neutron-star-matter Equations of State (EoSs) that interpolate between state-of-the-art theoretical results at low and high baryon density. Comparing to results from similar calculations prior to the tidal deformability constraint, we witness a dramatic reduction in the family of allowed EoSs. Based on our analysis, we conclude that the maximal radius of a 1.4-solar-mass is 13.4 km, and that smallest allowed tidal deformability of a similar mass star is {\Lambda}(1.4*M_sol) = 224.

Djuna Croon, Ann E. Nelson, Chen Sun, Devin G. E. Walker, Zhong-Zhi Xianyu

We show that neutron star binaries can be ideal laboratories to probe hidden sectors with a long range force. In particular, it is possible for gravitational wave detectors such as LIGO and Virgo to resolve the correction of waveforms from ultralight dark gauge bosons coupled to neutron stars. We observe that the interaction of the hidden sector affects both the gravitational wave frequency and amplitude in a way that cannot be fitted by pure gravity.