First Surface‐resolved Results with the Infrared Optical Telescope Array Imaging Interferometer: Detection of Asymmetries in Asymptotic Giant Branch Stars

Abstract

We have measured non-zero closure phases for about 29% of our sample of 56\nnearby Asymptotic Giant Branch (AGB) stars, using the 3-telescope Infrared\nOptical Telescope Array (IOTA) interferometer at near-infrared wavelengths (H\nband) and with angular resolutions in the range 5-10 milliarcseconds. These\nnonzero closure phases can only be generated by asymmetric brightness\ndistributions of the target stars or their surroundings. We discuss how these\nresults were obtained, and how they might be interpreted in terms of structures\non or near the target stars. We also report measured angular sizes and\nhypothesize that most Mira stars would show detectable asymmetry if observed\nwith adequate angular resolution.\n