The Influence of Forming Companions on the Spectral Energy Distributions of Stars with Circumstellar Discs

We study a possibility to detect signatures of brown dwarf companions in a circumstellar disc based on spectral energy distributions. We present the results of spectral energy distribution simulations for a system with a 0.8 M-circle dot central object and a companion with amass of 30M(J) embedded in a typical protoplanetary disc. We use a solution to the one-dimensional radiative transfer equation to calculate the protoplanetary disc flux density and assume, that the companion moves along a circular orbit and clears a gap. The width of the gap is assumed to be the diameter of the brown dwarf Hill sphere. Our modelling shows that the presence of such a gap can initiate an additional minimum in the spectral energy distribution profile of a protoplanetary disc at lambda = 10-100 mu m. We found that it is possible to detect signatures of the companion when it is located within 10 AU, even when it is as small as 3 M-J. The spectral energy distribution of a protostellar disc with a massive fragment (of relatively cold temperature similar to 400 K) might have a similar double peaked profile to the spectral energy distribution of a more evolved disc that contains a gap.