FU Orionis Resolved by Infrared Long-Baseline Interferometry at a 2 AU Scale

Abstract

We present the first infrared interferometric observations of a young stellar object with a spatial projected resolution better than 2 AU. The observations were obtained with the Palomar Testbed Interferometer (PTI). FU Orionis exhibits a visibility of for a m–projected baseline at mm. On the 2 V ϭ 0.72 ‫ע‬ 0.07 103 ‫ע‬ 5 l ϭ 2.2 spatial scale probed by the PTI, the data are consistent with both a binary system scenario (a maximum magnitude difference of mag and the smallest separation of AU) and a standard luminous accretion 2.7 ‫ע‬ 0.5 0.35 ‫ע‬ 0.05 disk model (M , yr Ϫ1), where the thermal emission dominates the stellar scattering, and are Ϫ5 ˙ M ∼ 6 # 10 inconsistent with a single stellar photosphere.