Year: 2019
Type: article
Abstract: Binary pulsars provide some of the tightest current constraints on modified theories of gravity and these constraints will only get tighter as radio astronomers continue timing these systems. These binary pulsars are particularly good at constraining scalar–tensor theories in which gravity is mediated by a scalar field in addition to the metric tensor. Scalar–tensor theories can predict large deviations from general relativity due to the fact that they allow for violation of the strong-equivalence principle through a phenomenon known as scalarization. This effect appears directly in the timing model for binary pulsars, and as such, it can be tightly constrained through precise timing. In this paper, we investigate these constraints for two scalar–tensor theories and a large set of realistic equations of state. We calculate the constraints that can be placed by saturating the current bounds on single post-Keplerian parameters, as well as employing Bayesian methods through Markov-chain-Monte-Carlo simulations to explore the constraints that can be achieved when one considers all measured parameters simultaneously. Our results demonstrate that both methods are able to place similar constraints and that they are both indeed dominated by the measurements of the orbital period decay. The Bayesian approach, however, allows one to simultaneously explore the posterior distributions of not only the theory parameters but of the masses as well.
Source: Classical and Quantum Gravity
Authors: David Anderson, Paulo Freire, Nicolás Yunes
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: bronze
Awards: THIS PROPOSAL IS FOCUSED ON (I) NUCLEAR PHYSICS IN EXTREME GRAVITY (II) EXPERIMENTAL RELATIVITY IN EXTREME GRAVITY AND (III) MULTIMESSENGER ASTROPHYSICS IN EXTREME GRAVITY. REGARDING (I) WE PROPOSE TO IMPROVE AND DEVELOP NEW TOOLS TO EXTRACT THE MOST ASTROPHYSICS FROM X-RAY DATA OBTAINED WITH NASA'S NEUTRON STAR INTERIOR COMPOSITION EXPLORER (NICER). THESE TOOLS WILL ALLOW FOR PRECISE CONSTRAINTS ON THE NEUTRON STAR EQUATION OF STATE THROUGH MEASUREMENTS OF THEIR MASS AND RADIUS. REGARDING (II) WE PROPOSE TO CREATE A FRAMEWORK THROUGH WHICH TO TEST GENERAL RELATIVITY WITH BOTH GRAVITATIONAL WAVE DATA FROM THE LASER INTERFEROMETER SPACE ANTENNA (LISA) AND X-RAY DATA FROM NICER IN A ROBUST AND MODEL-INDEPENDENT FASHION. THIS FRAMEWORK WILL ALLOW FOR CONSISTENCY CHECKS OF EINSTEIN'S THEORY AND THE SEARCH FOR MODIFIED GRAVITY ANOMALIES WITH NEUTRON STARS AND BLACK HOLES. REGARDING (III) WE PROPOSE TO LEARN ABOUT NUCLEAR PHYSICS AND GENERAL RELATIVITY BY COMBINING X-RAY INFORMATION FROM NICER GAMMA-RAY INFORMATION FROM NASA'S FERMI AND SWIFT TELESCOPES AND GRAVITATIONAL WAVE INFORMATION FROM ADVANCED LIGO. THE PROPOSED WORK IS OF DIRECT RELEVANCE TO NASA'S STRATEGIC MISSION TO BETTER UNDERSTAND THE UNIVERSE THROUGH OBSERVATION AND NASA'S MISSION OF DISCOVERY AND KNOWLEDGE. THE REGION OF THE UNIVERSE WHERE GRAVITY IS UNBEARABLY STRONG AND DYNAMICALLY CHANGING (THE EXTREME GRAVITY UNIVERSE) IS ONE OF THE LAST UNTURNED STONES. THIS IS IN PART BECAUSE EXTREME GRAVITY OBJECTS LIKE NEUTRON STARS AND BLACK HOLES ARE DIFFICULT TO RESOLVE DUE TO THEIR SIZE AND DISTANCE FROM EARTH. NASA'S INVESTMENTS IN NEUTRON STAR ASTROPHYSICS AND IN SPACE-BORNE GRAVITATIONAL WAVE ASTROPHYSICS ARE AIMED AT RESOLVING SUCH OBJECTS AND FOR THE FIRST TIME EXPLORING THE EXTREME GRAVITY UNIVERSE IN DETAIL. THE FOCUS OF THIS PROPOSAL IS TO AID IN THIS ENDEAVOR BY DEVELOPING THE TOOLS AND THE UNDERSTANDING NEEDED TO EXTRACT THE MOST INFORMATION FROM THE DATA., A SPACE BASED GRAVITATIONAL WAVE DETECTOR WILL OPEN UP THE SOURCE RICH LOW FREQUENCY PORTION OF THE SPECTRUM THAT CAN NOT BE ACCESSED FROM THE GROUND, The Extreme Gravity Dynamics and Gravitational Waves of Generic Compact Binary Inspirals
OpenAlex ID: W2907688498