Conveners
Electromagnetic Counterparts of Compact Binary Mergers: Block 1
- Paz Beniamini (Caltech)
- Jonathan Granot (The Open University of Israel)
Description
Electromagnetic (EM) counterparts of merging compact binaries containing neutron stars (two neutron stars or a neutron star and a black hole) can arise from different components of the merger ejecta. Examples include the prompt gamma-ray signal associated with emission from the relativistic jet or cocoon, the multi-wavelength afterglow associated with the interaction of the jet with the surrounding medium, the kilonova resulting from the r-process heated ejecta and the kilonova afterglow arising from the interaction of the latter ejecta with its environment. The first detection of a gravitational wave signal from a binary neutron star merger, GW 170817, has vividly confirmed three of these predicted EM counterparts, as its violent burst of gravitational waves was accompanied by the short GRB 170817A, a spectacular kilonova and a long-lived afterglow. This triple association has already significantly boosted our understanding of each of those components individually and helps us construct a more comprehensive picture of compact binary mergers in an astrophysical context. Furthermore, it has even enabled us to put significant constraints on topics of broad interest in physics from the neutron star equation of state to the expansion rate of the Universe. It is an exceptional demonstration of the power of multi-messenger astrophysics. Future compact binary mergers detected in gravitational waves and / or EM counterparts and further observations of the (still detectable) EM counterparts of GW 170817, therefore hold great promise to boost our understanding further. This session aims to explore the lessons learned from the observed counterparts and to prepare the community for future detections.
I will provide a critical review of what we learned from the NS-NS merger GW170817 during year of electromagnetic follow up across the spectrum. Specifically, I will focus on recent developments from our coordinated radio-X-ray monitoring campaign that revealed the emergence of a new component of emission.
The outcome of a binary neutron star depends sensitively on the mass of the binary and the equation of state of dense nuclear matter. All else being equal, lower mass binaries tend to produce rapidly rotating magnetar remnants that survive longer (if not indefinitely) before collapsing into black holes. I will discuss some of the implications of the resulting diversity imprinted by a range...
The unprecedented coincident detection of a short gamma-ray burst (GRB) with gravitational waves from a binary neutron star (BNS) merger in GW170817/GRB170817A, followed by the long-lasting broadband afterglow, put our understanding of the structure of GRB jets to the test. GRB170817A turned out to be a particularly interesting event, due to its nearby distance (~40 Mpc) and emission from an...
Radio afterglows of neutron star mergers are excellent probes of the fast ejecta (relativistic jets and fast tail of the dynamical ejecta) and provide strong constraints on the inclination angle, ejecta morphology and energetics. This information is complementary to the ejecta mass and composition derived from the early-time UV-optical-infrared emission (called the kilonova/macronova). Radio...
The CALorimetric Electron Telescope (CALET) cosmic ray detector on the International Space Station (ISS) has been in operation since its launch in 2015.
The main instrument, the CALorimeter (CAL), is monitoring the gamma ray sky from ~1 GeV up to ~10 TeV with a field-of-view of about 2 sr for more than five years.
In this paper, we describe the analysis of gamma ray candidate events observed...
The connection between binary neutron star mergers and short gamma-ray bursts (GRBs) was solidified by the simultaneous detection of GW170817 and GRB 170817A. These events were followed by bright kilonova emission arising from the radioactive decay of freshly synthesized r-process ejecta, which were expelled during the neutron star merger. Kilonova emission is a fundamental signature of...
When two Neutron Stars (NSs) merge a multi-band electromagnetic (EM) emission, known as Kilonova (KN), follows. It is believed to be powered by the radioactive decay of ejecta products. In this contribution we discuss how future measurements of KN light curves and spectra could constrain some interesting features of the NSs in the coalescing binary. In particular we will focus on the impact...
A kilonova signal is generally expected after a Black Hole - Neutron Star merger. The strength of the signal is related to the Equation of State of neutron star matter and it increases with the stiffness of the latter. The recent results obtained by NICER suggest a rather stiff Equation of State and the expected kilonova signal is therefore strong, at least if the mass of the Black Hole does...
The rich EM phenomenology in the first few hours after a compact object merger encodes the nature of the post-merger remnant, and a wide array of other compelling physics. Unfortunately, the requirement to find, and classify a counterpart within the large GW localization regions before followup with sensitive instruments can begin, excludes access to these first few hours, even for the most...
GRB 170817A was markedly dissimilar to any other detected short gamma-ray burst as it was observed off-axis. This was further made evident by the information gained from the accompanying observation of GW170817. The event has since sparked discussion into the short gamma-ray burst beam profile and how it can link the observed luminosity of GRB 170817A with the rest of the observed on-axis...
