Introduction

We study neutron star astrophysics and gravitational waves.

Neutron stars are the collapsed remnants of massive stars, the most compact astrophysical objects outside of black holes, and the place where matter makes it's last stand against the overwhelming force of gravity. Inside a neutron star, matter is compressed into strange new forms, pushing the limits of our understanding of condensed matter and particle interactions.

Like many stars, neutron stars can be found in binary systems, where pairs of neutron stars orbit. As they do so, they lose energy to gravitational waves, eventually spiraling towards each other and colliding. This will release huge amounts of energy in gravitational-wave signals that LIGO, the Laser Interferometer Gravitational-wave Observatory, hopes to observe. These collisions may also explain some of the Gamma Ray Bursts seen by space telescopes like NASA's Fermi.

You can read more about gravitational-wave physics at CSUF at the webpage for the Center for Gravitational-Wave Physics and Astronomy.

My group and I work to understand and model how neutron stars interact, collide, and radiate energy, so that observations can tell us new things about their structure and composition.

You can see a full list of things I've worked on at the Google Scholar Citations Page for Jocelyn Read

Research Group

My research relies on the hard work of many students here at CSUF. They include:

Areas of Research

Dense matter and gravitational waves

We search for the gravitational-wave signals from binary systems in LIGO data using templates calculated from the expected motions of the two objects. For systems involving neutron stars, most of this motion is approximate. Each neutron star or black hole is described by a point mass, and we add relativistic corrections to the Newtonian dynamics of the system.

The best indirect evidence for the existence of gravitational waves described by General Relativity comes from observing the binary dynamics of nearby neutron-star systems like the double pulsar system PSR J0737-3039 and comparing it to these approximate models.

The systems we observe in our neighborhood aren't detectable by LIGO; they orbit each other every few hours and radiate weakly. LIGO could only see them only after they spiral into tight enough orbits that they zip around more than ten times per second. For the systems we see in our galaxy, this won't happen for many millions of years. However, Advanced LIGO will be able to listen to many galaxies at a time; enough that we expect to catch about forty of these binary neutron star mergers every year.

The point-particle and post-Newtonian description will inevitably break down as the stars make their final approach; tidal forces will begin to distort the stars, and then their gravitational interaction will no longer have only small corrections to the Newtonian dynamics. Eventually, when the two stars crash into each other, their behavior won't be well-described by an orbit at all. Numerical simulations are required to understand what happens then.

Student projects

Incorporate tidal terms with realistic coefficients into the waveforms used by the LIGO Scientific Collaboration (the LIGO Algorithm Library,) so that they can be used in parameter estimation studies and to analyze future gravitational-wave detections.

Where will the templates used to search for gravitational waves break down? Use results of post-Newtonian calculations and numerical simulations to determine; when matter effects might lead to mistaken flags for poor waveform matches, or where they might contaminate parameter estimation.

Crust shattering and gamma-ray flares

A recent project looks at what might cause small flares before the main Gamma Ray Burst in a merging neutron star scenario. You can read a synopsis in Physics from a recent Physical Review Letters publication which was an Editor's Suggestion. My collaborator Dave Tsang has a webpage explaining the resonant shattering scenario.

Student projects

The crust response to the tidal field of the other star has not been fully explored. Even though this probably won't crack the crust directly, perhaps it would trigger other effects. How do different crusts get strained by tidal forces?

The frequency of the resonance depends on properties of the neutron-star matter. We have only looked at a few examples. Can we find systematic relationships between features of the equation of state and the frequency of the shattering resonance?

Research projects for students

Research in astrophysics will let you learn more about the Universe and help push the frontiers of human knowledge. Each research student can personally contribute something new to the scientific community.

The skills you build doing research will give you a head start for a future academic career. They are also used outside of physics. Each student will produce a publically-viewable portfolio of work: open-source code repositories, online demos and writeups, documentation, and/or published papers. Specific things you can work on:

  • Using python, a scripting language: a workhorse in astronomy as well as other sciences, used in today's software industry.
  • Use of modules like numpy (numeric python) and scipy (scientific python)
  • Use of Mathematica, matlab/pylab
  • Code development in c/c++
  • Unix-style command-line interface
  • Submitting jobs to computer clusters for parallel processing. Managing clusters. Writing parallelizable code.
  • Data analysis: dealing with big data. Pattern matching. Signal processing.
  • Technical writing. The LaTeX typesetting system.
  • Making clear figures and graphical communication.
  • Writing web demos for outreach, teaching, and illustrating ideas.
  • Applied mathematics:
    • working with general relativity, understanding coordinates, framing differential equations, using perturbation theory.
    • Developing mathematical models,
    • Statistics and data analysis.