Image credit: X-ray: NASA/CXXC/UMass/D. Wang et al.; Optical: NASA/ESA/STScI/D. Wang et al.; IR: NASA/JPL-Caltech/SSC/S. Stolovy

High Energy Astrophysics

We look at many different aspects of neutron stars, pulsars, X-ray binaries, and supernova remnants to answer fundamental questions about compact object physics, Galactic cosmic-ray production and propagation, particle acceleration mechanisms, accretion physics, and the population of Galactic X-ray sources as a whole (including neutron stars, black holes, X-ray binaries, micro-quasars).

Neutron stars are collapsed stars whose surfaces are hot enough to emit radiation in ultraviolet and X-rays. In addition, young neutron stars with active (populated with particles) magnetospheres manifest themselves as pulsars - objects that emit short but intense bursts of radio waves, X-rays, or visible electromagnetic radiation at regular intervals. Due to the extreme conditions in the neutron star interiors, these objects can be used as natural laboratories for studying the poorly understood properties of the superdense, strongly magnetized, superconducting matter. Such conditions can never be reproduced in Earth laboratories and therefore studying neutron stars provides the only way to learn about the nuclear reactions and interactions of the elementary particles under these extreme conditions. This information is of fundamental importance for particle and quantum field physics. Studying pulsar winds allows one to understand the complicated PWN morphologies, elucidate the dynamics of relativistic magnetized outflows and their interaction with the ambient medium and extremely efficient (up to PeV energies) particle acceleration in relativistic magnetized outflows. The mentioned physical processes are also relevant for a wide range of astrophysical phenomena (e.g. AGN and micro-quasar jets).

We also study dynamics of accretion flows and jets in accreting black hole and neutron star binaries as well as accretion flows fueling supermassive central black holes in the galaxies. These tell us about extreme astrophysical environments near black holes and probe the physics of accretion such as angular momentum transfer and connection between the accretion disk and jets.

Current active research areas: 1) pulsar winds and pulsar-wind nebulae, 2) thermal emission from neutron stars, 3) galactic GeV/TeV sources, 4) interaction processes in tight relativistic binaries, 5) modeling of relativistic magnetized outflows, 6) extended emission from microquasars, 7) searching galactic surveys for compact objects, 8) studies of X-ray source population near the Galactic center, and 9) searches for nearby, relic neutron stars and isolated black holes (theory and observations) . We are actively engaged in radio, optical, X-ray, and gamma-ray observations that provide valuable diagnostics of all these processes. Current observing projects involve VLA and ATCA, Hubble Space Telescope, Chandra X-ray Observatory, XMM-Newton, Suzaku, Fermi, and VERITAS. Our group has representation in the Chandra ACIS team and VERITAS collaboration.

Faculty Research

Neutron stars, pulsars, pulsar winds, astrophysical jets, black holes, accretion flows in binaries and galaxies, microquasars, Galactic Center population, X-ray, TeV, cosmic rays.

Stephen Eikenberry

Jonathan Tan