Session E07: Astrophysics: Binary Systems

Black holes, neutron stars, and gravitational waves

Recently, LIGO and VIRGO have detected the first gravitational waves from binary black hole mergers, and one binary neutron star merger. This latter event, GW170817, was particularly exciting because it was also observed in the electromagnetic spectrum, from gamma-rays to the radio, making it truly a multi-messenger event. The detections of binary mergers provide a new way to study compact objects--black holes and neutron stars--in the universe. I will discuss some of the scientific questions that gravitational waves will help us address, such as testing general relativity, studying matter inside neutron stars, learning how large black holes can form, and finding the origin of heavy elements in the universe. I will also discuss computational models of merging binaries that help us interpret the gravitational wave data, and introduce Dendro-GR, the new computer code we are using to study intermediate-mass black holes.   

Towards modeling high mass ratio binary black hole inspirals and mergers

Einstein's general theory of relativity has made various accurate predictions in the relatively weak gravitational fields of our solar system. Gravitational wave astronomy has provided scientists with the opportunity to test general relativity in the strong gravitational fields of binary black hole mergers. Massively parallel numerical relativity codes have modeled black hole inspirals and mergers and obtained the resulting gravitational waveforms. As the mass ratio of the two black holes is increased, the computational time required to model the system rises as well. We present a new code, Dendro-GR, which when fully functional will be able to model binary black hole inspirals and mergers with mass ratios of up to 100:1. This represents a significant improvement over the current highest mass ratio modeled of 15:1. Dendro-GR has demonstrated excellent weak scalability up to 131K cores, and has a variety of techniques included to numerically solve partial differential equations.  We also present a Dendro-GR sub-module which solves the Maxwell Equations and compare our results to other results presented in the literature, suggesting that the full Dendro-GR code is nearly ready to generate previously unknown gravitational waveforms.   

Numerical relativity and simulating merging compact object binaries with very different masses

The intersection of general relativity and computational physics has provided important theoretical input for the recent detection of gravitational waves.  Indeed, numerical relativity is likely to continue providing important insights to the emerging field of gravitational wave astronomy.   We will review some of this work together with some of the computational ingredients necessary to simulate sources of gravitational radiation; one example being binary compact objects of roughly equal mass.  We will also describe some current work and some of the additional computational elements needed to simulate binaries of very different mass ratios.

  

Data integration challenges in astronomy

Astronomical objects emit electromagnetic waves at different wavelengths from radio waves to gamma-rays. Measurements obtained with each wavelength bring a unique piece of information about the environment of the object. Different instruments at different wavelengths have observed astronomical objects with unprecedented quality. However, integrating these data to form a coherent view is a challenging task. Recent, rapid development of software algorithms allow us to develop frameworks to incorporate low-level data that comes in different formats and have different handling procedures. We are developing a framework, called 3ML, for combining data from astronomical observations made with different instruments to form a coherent model. I will present the challenges of data integration, the structure of the 3ML framework, and updates from our work on generating a multi-wavelength compatible model for the Crab Pulsar Wind Nebula.