A new distance scale for GRBs: The local group halo

Abstract

I would like to propose a new distance scale to Gamma Ray Bursters, where the characteristic distance is Megaparsecs. This distance scale is intermediate between those of the familiar galactic models (D∼100 kpc) and cosmological models (D∼1 Gpc). I envision bursters as being neutron stars shot with high velocities (>1000 km/s) out of our own Milky Way galaxy as well as nearby galaxies in the Local Group. The existence of such high velocity neutron stars has been recently discovered, and the inevitable fate of these is to escape the galaxy at high speeds. After a Hubble Time, these escapees can travel over 10 Mpc. I adopt the proposal by Duncan and Thompson that the high velocities are caused by extremely large magnetic fields, which will also beam the gamma rays into small cones directed along the velocity vector. With this preferred beaming, the Solar System will see bursts primarily coming from galaxies near our own. As such, my new distance scale is associated with a halo of neutron stars emitted by ou...