Searches for Periodic Modulation in Astronomical Gamma-ray and X-ray Sources
Dr. Robin Corbert, Center for Space Sciences and Technology.
Binary star systems containing a compact object i.e. a neutron star, black hole or white dwarf, can be strong emitters of X-ray and gamma-ray emission. This can be modulated on several timescales including the spin period of the compact object, the orbital period of the system, and poorly understood coherent modulation on periods longer than the orbital period (“superorbital modulation”). Long-term light curves provided by missions such as the Fermi and Swift satellites, and the MAXI instrument on the International Space Station can provide a means of detecting these periodicities from light curves that are ~20 years long. From searches for this modulation we have previously identified modulation from gamma-ray binaries, which are a very rare class of object, and also modulation on spin, orbital and superorbital periods in X-ray binaries. We are now also starting to detect modulated high-energy emission from a number of white dwarf systems known as cataclysmic variables.