Michael J. Ireland

Photonic mid-infrared nulling for exoplanet detection on a planar chalcogenide platform

In exoplanet interferometry a null of 40~dB is a large step in achieving the ability to directly image an Earth-like planet that is in the habitable zone around a star like our own. Based on the standard procedure at the Australian National University we have created a nulling interferometer that has achieved a 25~dB null in the astronomical L~band under laboratory conditions. The device has been constructed on a 2-dimensional platform of chalcogenide glass: a three layered structure of

Image-plane fringe tracker for adaptive-optics assisted long baseline interferometry

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Planetary system, star formation, and black hole science with non-redundant masking on space telescopes

undercladding, 2~si{um} of

CHARA Array Measurements of HR 8799 and Their Implications for the Imaged Companions

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The Interferometric Orbit and Fundamental Parameters for Spica from the CHARA and SUSI Arrays

core and an angled deposition of

Elemental abundances of {alpha} Cir (Bruntt+, 2008)

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Compact Dust Shells Around Massive Evolved Stars

as a complete overcladding. Matching simulation from Rsoft and individual results of the MMIs the expected null should produce a null of 40~dB over a bandwidth of 400~nm but due to limitations in mask design and light contamination only a 25~dB extinction can be reliably achieved.The future of exoplanet detection lies in the mid-infrared (MIR). The MIR region contains the blackbody peak of both hot and habitable zone exoplanets, making the contrast between starlight and planet light less extreme. It is also the region where prominent chemical signatures indicative of life exist, such as ozone at 9.7 μm. At a wavelength of 4 μm the difference in emission between an Earth-like planet and a star like our own is 80 dB. However a jovian planet, at the same separation exhibits 60 dB of contrast, or only 20 dB if it is hot due to its formation energy or being close to its host star. A two dimensional nulling interferometer, made with chalcogenide glass, has been measured to produce a null of 20 dB depth, limited by scattered light. Measures to increase the null depth to the theoretical limit of 60 dB are discussed.

Angular Diameters, Temperatures, And Luminosities Of Massive Stars: Prospects For Sim-lite

Accurate fringe tracking is essential for sensitive long-wavelength thermal background limited operation of the current Very Large Telescope Interferometry (VLTI) and future Planet Formation Imager (PFI) facilities. We present and simulate a dual fringe tracking and low-order adaptive optics concept based on a combination of non-redundant aperture interferometry and eigenphase in asymmetric pupil wavefront sensing. This scheme can acquire fringes at many wavelengths of path length offset between telescopes, even with moderate tilt offset and pupil shifts between beams. Once locked to fringes, our technique can also be used for simultaneous low-order wavefront sensing, and has near-optimum sensitivity where there is a dominant point-source image component. This concept is part of the Heimdallr visitor instrument currently being investigated for VLTI.