Benchmark problems for wavelength dependent continuum radiative transfer

When verifying a sophisticated numerical code, it is a usual practice to compare the results with reliable solutions obtained by other means. This work provides such solutions for the wavelength dependent dust radiative transfer problem. We define a set of benchmark problems in spherical geometry and solve them by three radiative transfer codes which implement different numerical schemes. Results for the dust temperature and emerging spectra agree to better than 0.1%, and can be used as benchmark solutions for the verification of the dust radiative transfer codes.