  The relationship between gravitational anomalies and Hawking radiation of
black holes was revealed by Wilczek and Robinson. In this study, we apply their
method to an analogue de Sitter spacetime in the quantum Hall system with an
expanding edge. Because this system is chiral, there is no need to impose the
condition of ingoing modes near the horizon, which was assumed in the original
method. Moreover, this system is structured so that the de Sitter space is
sandwiched between two flat spaces, and although the effects of the anomaly
would not appear in an ordinal de Sitter spacetime, they manifest themselves as
boundary conditions between the de Sitter and the flat regions. By performing
calculations under these boundary conditions, we obtain the flux of Hawking
radiation in the outer flat region with the Gibbons-Hawking temperature of the
de Sitter horizon.
