Low-mass protoplanetary disk of the herbig Ae star DDser: Thermal radiation of dust and possible presence of massive planets

We detected thermal IR radiation from DDSer, a low-activity UXOri-type star, the source of which is a disk with a complex structure (an inner ring with the dust temperature of about 900 K and an outer disk with the temperature below 300 K). The 15.1-year period, which we estimated from our longterm photometric observations, indicates the perturbation of this ring by a low-mass companion (a planet perhaps) with an orbital radius of 8 a.u. In general, the detected characteristics of the DDSer disk (a dust ring with the densitymodulated with a 10-year scale period, the presence of compact dust clumps inside the ring's inner lobe) are almost identical to the characteristics of the RZ Psc disk, where an active asteroid belt inside the orbit of a planet or a similar low-mass companion is assumed. Although the suggestion about a collisional source of the dust in these systems is disputable, the complex structure of their disks,manifested in the IR spectrum shape and photometric variability, especially the long-period variability, gives evidence for massive planets already formed in these systems.