Status and Future Prospects for Gamma-Ray Polarimetry.pdf

a r X i v : a s t r o - p h / 0 5 0 8 3 1 5 v 1 1 4 A u g 2 0 0 5 Chin. J. Astron. Astrophys. Vol. 0, No. 0, (200x) 000–000 (http:/ ) Chinese Journal of Astronomy and Astrophysics Status and Future Prospects for γ-ray Polarimetry M. L. McConnell1 ? and P. F. Bloser1 Space Science Center, University of New Hampshire, Durham, NH 03824 Received 2001 month day; accepted 2001 month day Abstract The recent detection of linear polarization from GRB120206 has piqued the interest of the community in this relatively unexplored avenue of research. Here, we review the current status and prospects for GRB polarimetry at hard X-ray and soft γ-ray energies. After reviewing the most recent results, we present a brief survey of current and planned experiments that are capable of making GRB polarization measurements in the energy range between 30 keV and 30 MeV. Key words: instrumentation: polarimeters — gamma rays: bursts — gamma rays: observations — polarization — Sun: X-rays, gamma rays 1 INTRODUCTION For many years, polarimetry has been used as a useful tool throughout much of the electro- magnetic spectrum. At high photon energies, however, astronomers have been slow to adopt polarimetry as a standard tool. This has been both because of the experimental difficulty in making such a measurement and because the levels of polarization were expected to be quite low. Even at lower X-ray energies (1–10 keV), where source fluxes are considerably greater, the community has been slow to embrace the potential value of polarimetry. All this may have changed, however, with the recent detection of γ-ray polarization from GRB021206. This result, although controversial, has served to invigorate interest in this area. This paper provides a brief overview of the experimental status and future prospects of polarimetry at energies above ～ 30 keV. 2 SCIENCE BACKGROUND Many emission processes that can generate γ-ray photons can also result in the linear polar- ization of those photons (e.g., Le