Using the sub-milli-arcsecond resolution of the CHARA interferometer array and
combining light with the 2-telescope combiner CHARA Classic, we have detected
strong near-infrared (NIR) emission interior to the dust-sublimation radius of
Herbig Ae stars MWC275 and AB Aur. The large contribution of this emission
component, which we argue to be hot gas, to the total NIR spectral energy distribution
(SED) is not predicted by current models of the dust evaporation front,
indicating that the NIR disk is more complicated than expected. Furthermore,
we demonstrate that the structure of the evaporation front in MWC275 is time
variable, making single epoch, large uv coverage observations critical to decoding
front geometry. With the commissioning of CHARA Michigan Phase Tracker
in the summer of 2008, the Michigan Infrared Combiner (a 6 telescope combiner
at CHARA) will become an ideal instrument for studying the evaporation
front, achieving the required sensitivities to begin the first "true" interferometric
imaging of the gas-dust transition region in young stellar objects (YSOs).
Here, we summarize results on the evaporation front structure obtained with
CHARA Classic and describe future prospects with CHARA MIRC in elucidating
morphology of the gas-dust transition region.
We report the first scientific results from the Michigan Infrared Combiner (MIRC), including the first resolved
image of a main-sequence star besides the Sun. Using the CHARA Array, MIRC was able to clearly resolve the
well-known elongation of Altair's photosphere due to centrifugal distortion, and was also able to unambiguously
image the effect of gravity darkening. In this report, we also show preliminary images of the interacting binary
β Lyr and give an update of MIRC performance.
The Michigan Infrared Combiner (MIRC) has been designed for two primary goals: 1) imaging with all six CHARA telescopes simultaneously in the near-infrared, 2) direct detection of "hot Jupiter" exoplanets using precision closure phases. In September 2005, MIRC was commissioned on-sky at the CHARA Array on Mt. Wilson, CA, successfully combining light from 4 telescopes simultaneously. After a brief overview of MIRC features and design philosophy, we provide detailed description of key components and present results of laboratory tests. Lastly, we present first results from the commissioning run, focusing on engineering performance. We also present remarkable on-sky closure phase results from the first night of recorded data with the best-ever demonstrated closure phase stability and precision (ΔΦ = 0.03 degrees).