Limits to the analogue Hawking temperature in a Bose-Einstein condensate

Quasi-one dimensional outflow from a dilute gas Bose-Einstein condensate reservoir is a promising system for the creation of analogue Hawking radiation. We use numerical modeling to show that stable sonic horizons exist in such a system under realistic conditions, taking into account the transverse dimensions and three-body loss. We find that loss limits the analogue Hawking temperatures achievable in the hydrodynamic regime, with sodium condensates allowing the highest temperatures. A condensate of 30,000 atoms, with transverse confinement frequency omega_perp=6800*2*pi Hz, yields horizon temperatures of about 20 nK over a period of 50 ms. This is at least four times higher than for other atoms commonly used for Bose-Einstein condensates.