Vol. 617
In section 1: Letters to the Editor

Surface waves in protoplanetary disks induced by outbursts: Concentric rings in scattered light

This Letter presents a remarkably simple idea for treating the variations observed in circumstellar protoplanetary disks during outbursts of the central star. The authors propose that during an EXOr or FXOr event, the outer disk is sufficiently heated by irradiation that it is no longer static (it remains in global dynamical balance but expands and contracts to respond to the additional heating) and that this leaves a fingerprint in the line profiles. The response is wavelike in space because the time duration of the outburst is finite, the different parts of the circumstellar disk respond with different phases so it appears that a wave moves outward in the disk when t is actually only an excitation of a localized response. The time-delayed responses can also produce moving features in emission or absorption, and the light curves in different infrared bands will certainly show the effect.