John A. Tomsick

General Information

I am a Senior Fellow/Associate Director/Research Scientist at the University of California, Berkeley's Space Science Laboratory focusing on observations of compact objects (black holes, neutron stars, and even, occasionally, a white dwarf).  I have been involved in gamma-ray, X-ray, UV, optical, infrared, and radio observations of X-ray binaries, and I also am involved in instrumentation projects.  Please see my CV (pdf) for more  information.

Research

• X-Ray Binaries:  X-ray binaries are objects that consist of a normal star orbiting a neutron star or a black hole.  X-rays are produced when the compact object rips material off the normal star.  As the matter falls toward the compact object it forms an accretion disk.  In these systems, one finds the highest densities, strongest magnetic fields and strongest gravitational potentials in the universe, providing an opportunity to study extreme conditions and allowing for tests of physical theories in these conditions.  Many of these objects also produce relativistic jets and are sometimes called "microquasars" because of their similarity to the super-massive black holes found in quasars.
• Black hole spin:  I am interested in using X-ray observations to determine the spins of black holes in X-ray binaries.  Techniques for this include modeling reflection components and thermal emission from accretion disks.  It is especially interesting to compare the measured spins to the spins that are starting to be measured when black holes merge with other black holes, producing gravitational waves.
• Positron annihilation emission:  When electrons and positrons annihilate with each other, their rest mass is converted to photons.  This leads to an annihilation emission line at 511 keV, and an excess of this emission is seen coming from the Galactic bulge.  This very interesting signal is partly due to the decay of radioactive Al, but it may also be related to jets from black holes, certain types of supernovae, or X-ray binaries.  A connection to mysterious dark matter is also possible.
  

• The Nuclear Spectroscopic Telescope Array (NuSTAR): This satellite focuses high-energy X-rays from 3 to 79 keV.

• The Compton Spectrometer and Imager (COSI): This is a balloon mission sensitive to 0.2-5 MeV gamma-rays that had a 46 day flight in 2016.

• The Chandra X-ray Observatory:  Chandra provides unprecedented angular and spectral resolution for X-ray observations.

• International Gamma-Ray Astrophysics Laboratory:  INTEGRAL is a hard X-ray and gamma-ray mission.  It has excelled in taking hard X-ray images of the Galactic plane, and has been finding many new and interesting IGR sources.

• A Satellite for Astrophysics of Positrons and Polarization:  ASAPP is a SmallSat mission concept that operates in the 0.05-5 MeV range.
  

• See also the HEASARC page for information about other high energy observatories (XMM-Newton, Swift, Fermi) that I use for my research.