KH 15D: A Star Eclipsed by a Large-Scale Dusty Vortex?

We propose that the large photometric variations of KH15D are due to aneclipsing swarm of solid particles trapped in giant gaseous vortex rotating at\~0.2 AU from the star. The efficiency of the capture-in-vortex mechanismeasily explains the observed large optical depth. The weaker opacity atmid-eclipse is consistent with a size segregation of the particles toward thecenter of the vortex. This dusty structure must extend over ~1/3 of an orbit toaccount for the long eclipse duration. The estimated size of the trappedparticles is found to range from 1 to 10cm, consistent with the gray extinctionof the star. The observations of KH15D support the idea that giant vortices cangrow in circumstellar disks and play a central role in planet formation.Comment: Accepted in ApJ Letters - 4 pages - 2 figure