Future Prospects for MeV Polarimetry

Prof. Mark McConnell

University of New Hampshire / SwRI

Gamma ray polarimetry has the potential to provide important new insights into the underlying physics of astrophysical jets and other particle acceleration regions. Although gamma-ray polarimetry has not quite reached maturity as a useful astronomical tool, prospects are good that the next generation of MeV instruments will finally achieve important breakthrough measurements. Polarimetry is capable of probing relativistic jets over a range of Lorentz values, from galactic X-ray binaries, to active galactic nuclei (AGN), to gamma-ray bursts (GRBs). The acquisition of a definitive set of GRB polarization measurements will help to clarify the current picture of GRB polarization. Future polarization measurements of Cygnus X-1 will serve to (hopefully) verify the results from INTEGRAL, with subsequent observations extending these measurements to other galactic sources. Although there have not yet been any reported polarization measurements from AGN, there is every reason to expect that AGN gamma-ray emission is polarized. Polarimetry of the Crab nebula and solar flares will probe additional sites of particle acceleration. We will review the prospects for gamma-ray polarimetry, focusing on measurements in the Compton regime (roughly 0.2 - 30 MeV), where there exists the greatest potential for exciting new results. In particular, we will review the potential science to be gained from the next generation of gamma-ray instruments, including COSI, AMEGO and eASTROGAM.