The quest of gaining better insights into neutron stars has led a theorist in astrophysics at the University of Texas at Arlington (UTA) to study the explosive phenomena of X-ray bursts.
Nevin Weinberg, associate professor of physics, The University of Texas at Arlington. Image Credit: Randy Gentry/University of Texas at Arlington.
Nevin Weinberg, associate professor of physics, will head the study titled “Spectral and Radiation Hydrodynamic Models of Photospheric Radius Expansion X-ray Bursts.” The project will also involve students from UTA and physicists from the University of Virginia. This study is financially supported by a three-year grant from the National Science Foundation’s Division of Astronomical Sciences.
The formation of a neutron star happens when a massive star tends to explode in a supernova and the remains condense and crash upon themselves as a result of extremely strong gravitation. The packing of the material is done so tightly that electrons and protons integrate to form neutrons— thus the name called neutron stars is obtained.
If the neutron star is present in a binary system with another star, it can pull the material that is rich in hydrogen or helium from the other star that further develops a thin layer on its surface. As soon as the neutron star reaches the state of critical mass, this layer kindles in a thermonuclear explosion, thereby heating the complete surface of the neutron star to tens of millions of degrees Kelvin and discharging a quick burst of X-rays.
Nearly 20% of such X-ray bursts are known to be photospheric radius expansion (PRE) bursts. Here, the burst’s luminosity is so high that the radiation forces an optically thick wind that uplifts the photosphere (the outer shell from which light is radiated) off the surface of the neutron star.
Apart from a black hole, a neutron star is the most dense, compact known stellar object. It has a mass that’s one and a half to two times the mass of our sun, but a radius of only 10 kilometers, so it’s extremely compact. If you took a teaspoon of this material, it would weigh more than a billion tons.
Nevin Weinberg, Associate Professor of Physics, The University of Texas at Arlington
The advanced numerical simulation tools will be utilized by the study to offer the highly refined simulation of PRE X-ray bursts to date. The scientists will make a comparison of their results directly with observations made from the telescopes.
Neutron stars are interesting objects not just for astrophysics, but for fundamental physics. At these very high densities—densities higher than the nucleus of an atom—we don’t actually know how matter behaves.
Nevin Weinberg, Associate Professor of Physics, The University of Texas at Arlington
Since the 1970s, telescopes have been detecting X-ray bursts. However, there is still a lot that we don't know about them.
This is where our project comes in. We’re going to try to improve the models of X-ray bursts. The goal is to understand them better and to have a better agreement between the models and the observations, which will allow us to make more precise statements about the underlying neutron star that’s supporting the burst.
Nevin Weinberg, Associate Professor of Physics, The University of Texas at Arlington
The research team from UTA and the University of Virginia will explore the physics of PRE X-ray bursts through a combination of advanced computer models. The expected simulations will enable astronomers to better comprehend neutron stars, the burning processes during X-ray bursts and the composition of the wind expelled in the course of a burst.
Three years of financial support will be offered by the project for a graduate student in Weinberg’s research group. Also, it will enable him to mentor undergraduates from UTA’s Louis Stokes Alliances for Minority Participation Summer Research Academy. This offers study opportunities for students from groups historically underrepresented in STEM education.
Alex Weiss, professor, and chair of the UTA Department of Physics felt that Weinberg’s project could provide exciting new insights into the properties of neutron stars.
Weiss stated, “The computer simulations of X-ray bursts that will be used in this study, together with observations from X-ray telescopes, could provide answers to some of the questions we have about neutron stars. This project being led by Dr. Weinberg is a great example of the kind of innovative and collaborative work being done in the Department of Physics.”