Gravitational Waves and Gamma-Rays from a Binary Neutron Star Merger: GW170817 and GRB 170817A

Abstract

On 2017 August 17, the gravitational-wave event GW170817 was observed by the Advanced LIGO and Virgo detectors, and the gamma-ray burst (GRB) GRB170817A was observed independently by the Fermi Gamma-ray Burst Monitor, and the Anti-Coincidence Shield for the Spectrometer for the International Gamma-Ray Astrophysics Laboratory. The probability of the near-simultaneous temporal and spatial observation of GRB170817A and GW170817 occurring by chance is 5.0 10 8 -. We therefore confirm binary neutron star mergers as a progenitor of short GRBs. The association of GW170817 and GRB170817A provides new insight into fundamental physics and the origin of short GRBs. We use the observed time delay of 1.74 0.05 s +  () between GRB170817A and GW170817 to: (i) constrain the difference between the speed of gravity and the speed of light to be between 3 10 15 -´and 7 10 16 +´times the speed of light, (ii) place new bounds on the violation of Lorentz invariance, (iii) present a new test of the equivalence principle by constraining the Shapiro delay between gravitational and electromagnetic radiation. We also use the time delay to constrain the size and bulk Lorentz factor of the region emitting the gamma-rays. GRB170817A is the closest short GRB with a known distance, but is between 2 and 6 orders of magnitude less energetic than other bursts with measured redshift. A new generation of gamma-ray detectors, and subthreshold searches in existing detectors, will be essential to detect similar short bursts at greater distances. Finally, we predict a joint detection rate for the Fermi Gamma-ray Burst Monitor and the Advanced LIGO and Virgo detectors of 0.1-1.4 per year during the 2018-2019 observing run and 0.3-1.7 per year at design sensitivity.

Localization of binary neutron star mergers with second and third generation gravitational-wave detectors

“…This multimessenger data provided convincing answers to many outstanding questions. For instance, the detection of a short gamma ray burst (GRB) 1.7 seconds after GW170817 [24][25][26], and subsequent kilonova [27][28][29][30][31][36][37][38][39][40][41][42][43][44], confirmed that BNS mergers are a progenitor of these events. Lanthanide signatures in the kilonova light curves also showed BNS mergers to be a major site for nucleosynthesis of elements heavier than iron [40,44,47,48].…”

The Polarizations of Gravitational Waves

“…Finally, let us mention that Einstein-aether theory is highly constrained by various experimental observations, especially the speed bound derived from GW170817 and GRB 170817A [5,[43][44][45]. Apart from this speed bound and the absence of the gravitational Cherenkov radiation, there are constraints from the observations of pulsars (such as the post-Newtonian parameters, |α 1 | < 4 × 10 −5 [65] and |α 2 | < 2 × 10 −9 [66,67] …”

“…[33] also discussed the constraints that the generalized TeVeS theory should satisfy. Similarly to Einstein-aether theory, it is also constrained by the solar system test (i.e., the constraints on α 1 and α 2 2 ), the absence of the gravitational Cherenkov radiation, and the recent GW speed bound [45], etc. Taking all the constraints into account, it was found that the speed of the one 2 The expressions for α 1 and α 2 in generalized TeVeS theory are even more complicated, so they are not presented here, either.…”

“…Since the observation of GW170817 and GRB 170817A [5,43,44], many alternative theories of gravity have been highly constrained by the speed bound of the GW [45],…”

On the High-Energy Neutrino Emission from Active Galactic Nuclei

“…So when a magnetic jet system is newly established in a new direction [58] during a merger event, the jet flow has to be re-established (the characteristic velocity for this may be the relativistic speed of sound c/ √ 3), particles have be newly injected, and built up as a viable population. The observation of a time lag between the GW event and the HE photons [59] of 1.74 s is compatible with this characteristic distance for a central black hole of a mass of order 1 to 2 Solar masses: the characteristic distance introduced above yields a range of expected time lags of 10 −0.45 to 10 +1.05 s for a neutron star merger resulting in a black hole, fully compatible with the observations; the additional time lags due to the build-up of a viable population of energetic particles may be as fast or even faster. This time scales with the mass of the central black hole, and so the merger of two super-massive black holes of order 10 8 Solar masses the corresponding time scale is then about 3 years.…”