Hawking temperature and the bound on greybody factors in $D = 4$ double field theory

We investigate the basic properties of Hawking radiation for spherical solutions in $D = 4$ double field theory. We give the expression of the Hawking temperature for the solution and then discuss the results of various limits. We find that for all these limits only Schwarzschild solution and F-JNW solution can generate Hawking radiation. Moreover, we obtain the lower bound on greybody factors $\sigma_l(\omega)$ for the spherical solutions in $D = 4$ double field theory. In particular, we calculate the bound on greybody factors $\sigma_l(\omega)$ for F-JNW solution. For F-JNW solution, $\sigma_l(\omega)$ monotonically increases with the increase of $a(b)$ for fixed $b(a)$.