THE DISTANCE SCALE TO GAMMA-RAY BURSTS

We do not yet know the distance scale to gamma-ray bursts. Here I disc uss several observational results and theoretical calculations which p rovide evidence about the distance scale. First, I describe the recent discovery that many neutron stars have high enough velocities to esca pe from the Milky Way. These high-velocity neutron stars form a distan t, previously unknown Galactic ''corona.'' This distant corona is isot ropic when viewed from Earth, and consequently, the population of neut ron stars in it can easily explain the angular and brightness distribu tions of the BATSE bursts. If this were all of the evidence that we co nsidered, we could not distinguish the cosmological and Galactic hypot heses. I contend that we can go further, by considering other importan t evidence. I draw attention to the many similarities between soft gam ma-ray repeaters, which are known to be high-velocity neutron stars, a nd gamma-ray bursts. I point out that the source of the famous 1979 Ma rch 5 event, which is a high-velocity neutron star 50 kpc away from us , demonstrates that high-velocity neutron stars are capable of produci ng bursts which have the energy, the duration, and the spectrum of gam ma-ray bursts. Finally, I comment that high-velocity neutron stars in a distant Galactic corona can account for cyclotron lines and repeatin g, and naturally explain the absence of bright optical counterparts in gamma-ray-burst error boxes, whereas all of these present major diffi culties for cosmological models. I conclude that when we consider all of the evidence, it adds up to a strong case for the Galactic hypothes is.