A Planet as the Possible Cause of the HD 181327 Debris Disk Asymmetry

The debris disk around HD 181327 shows a significant asymmetry in its surface brightness profile when viewed in visible light. Observations from the Hubble Space Telescope STIS instrument show an arc of approximately 90○ of higher optical depth at a distance of 84 au from the star. Here we explore whether a planet could be the driver of this asymmetry. Through N-body simulations, we find that a 2–4 Jupiter-mass planet on a circular orbit at 70 au can produce and maintain a similar feature if the collisional lifetime of dust in the disk is between 4 and 8 kyr, so long as a modest fraction of the grains are ejected with high (≲1 km s−1) speeds. We also find that the surface brightness asymmetry is much less pronounced at larger particle sizes, which may account for the fact that observations of HD 181327 at longer wavelengths have not reported such an arc.