Monte-Carlo imaging for optical interferometry

We present a flexible code created for imaging from the bispectrum and V². By using a simulated annealing method, we limit the probability of converging to local chi-squared minima as can occur when traditional imaging methods are used on data sets with limited phase information. We present the results of our code used on a simulated data set utilizing a number of regularization schemes including maximum entropy. Using the statistical properties from Monte-Carlo Markov chains of images, we show how this code can place statistical limits on image features such as unseen binary companions

Monte-Carlo imaging for optical interferometry

We present a flexible code created for imaging from the bispectrum and V². By using a simulated annealing method, we limit the probability of converging to local chi-squared minima as can occur when traditional imaging methods are used on data sets with limited phase information. We present the results of our code used on a simulated data set utilizing a number of regularization schemes including maximum entropy. Using the statistical properties from Monte-Carlo Markov chains of images, we show how this code can place statistical limits on image features such as unseen binary companions

CHARA Michigan phase-tracker (CHAMP): a preliminary performance report

The CHARA Michigan Phase-tracker (CHAMP) is a real-time fringe tracker for the CHARA Array, a six-telescope long baseline optical interferometer on Mount Wilson, California. CHAMP has been optimized for tracking sensitivity at J, H, or K bands and is not meant as a science instrument itself. This ultimately results in maximum sensitivity for all the science beam combiners that benefit from stabilized fringes. CHAMP was designed, built, and tested in the laboratory at the University of Michigan and will be delivered to the CHARA Array in 2008. We present the final design of CHAMP, highlighting some its key characteristics, including a novel post-combination transport and imaging system. We also discuss testing and validation studies and present first closed-loop operation in the laboratory

Interferometry of ϵ\epsilon Aurigae: Characterization of the asymmetric eclipsing disk

We report on a total of 106 nights of optical interferometric observations of the $\epsilon$ Aurigae system taken during the last 14 years by four beam combiners at three different interferometric facilities. This long sequence of data provides an ideal assessment of the system prior to, during, and after the recent 2009-2011 eclipse. We have reconstructed model-independent images from the 10 in-eclipse epochs which show that a disk-like object is indeed responsible for the eclipse. Using new 3D, time-dependent modeling software, we derive the properties of the F-star (diameter, limb darkening), determine previously unknown orbital elements ($\Omega$, $i$), and access the global structures of the optically thick portion of the eclipsing disk using both geometric models and approximations of astrophysically relevant density distributions. These models may be useful in future hydrodynamical modeling of the system. Lastly, we address several outstanding research questions including mid-eclipse brightening, possible shrinking of the F-type primary, and any warps or sub-features within the disk.Comment: 105 pages, 57 figures. This is an author-created, un-copyedited version of an article accepted for publication in Astrophysical Journal Supplement Series. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from i

Last technology and results from the IOTA interferometer

The infrared optical telescope array (IOTA), one of the most productive interferometers in term of science and new technologies was decommissioned in summer 2006. We discuss the testing of a low-resolution spectrograph coupled with the IOTA-3T integrated-optics beam combiner and some of the scientific results obtained from this instrument

In the Shadow of the Transiting Disk: Imaging epsilon Aurigae in Eclipse

Eclipses of the single-line spectroscopic binary star, epsilon Aurigae, provide an opportunity to study the poorly-defined companion. We used the MIRC beam combiner on the CHARA array to create interferometric images during eclipse ingress. Our results demonstrate that the eclipsing body is a dark disk that is opaque and tilted, and therefore exclude alternative models for the system. These data constrain the geometry and masses of the components, providing evidence that the F-star is not a massive supergiant star.Comment: As submitted to Nature. Published in Nature April 8, 2010

CHARA Michigan phase-tracker (CHAMP): a preliminary performance report

The CHARA Michigan Phase-tracker (CHAMP) is a real-time fringe tracker for the CHARA Array, a six-telescope long baseline optical interferometer on Mount Wilson, California. CHAMP has been optimized for tracking sensitivity at J, H, or K bands and is not meant as a science instrument itself. This ultimately results in maximum sensitivity for all the science beam combiners that benefit from stabilized fringes. CHAMP was designed, built, and tested in the laboratory at the University of Michigan and will be delivered to the CHARA Array in 2008. We present the final design of CHAMP, highlighting some its key characteristics, including a novel post-combination transport and imaging system. We also discuss testing and validation studies and present first closed-loop operation in the laboratory

Michigan Infrared Combiner (MIRC): commissioning results at the CHARA Array

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)

Last technology and results from the IOTA interferometer

The infrared optical telescope array (IOTA), one of the most productive interferometers in term of science and new technologies was decommissioned in summer 2006. We discuss the testing of a low-resolution spectrograph coupled with the IOTA-3T integrated-optics beam combiner and some of the scientific results obtained from this instrument