Detecting a rotation in the ! Eridani debris disc

Theevidenceforarotationofthe" Eridanidebrisdiscisexamined.Dataat850-µmwavelength were previously obtained using the Submillimetre Common User Bolometer Array (SCUBA) over periods of 1997‐1998 and 2000‐2002. By # 2 fitting after shift and rotation operations, images from these two epochs were compared to recover proper motion and orbital motion of the disc. The same procedures were then performed on simulated images to estimate the accuracy of the results. Minima in the # 2 plots indicate a motion of the disc of approximately 0.6 arcsec per year in thedirectionofthestar’spropermotion.Thisunderestimatesthetruevalueof1arcsecperyear, implyingthatsomeofthestructureinthediscregionisnotassociatedwith" Eridani,originating instead from background galaxies. From the # 2 fitting for orbital motion, a counterclockwise rotation rate of ! 2. " 75 per year is deduced. Comparisons with simulated data in which the