The Fourier-Kelvin Stellar Interferometer (FKSI) is a mission concept for an imaging and nulling interferometer for the mid-infrared spectral region (5-30 microns). FKSI is conceived as a scientific and technological pathfinder to TPF/DARWIN as well as SPIRIT, SPECS, and SAFIR. It will also be a high angular resolution system complementary to NGST. The scientific emphasis of the mission is on the evolution of protostellar systems, from just after the collapse of the precursor molecular cloud core, through the formation of the disk surrounding the protostar, the formation of planets in the disk, and eventual dispersal of the disk material. FKSI will also search for brown dwarfs and Jupiter mass and smaller planets, and could also play a very powerful role in the investigation of the structure of active galactic nuclei and extra-galactic star formation. We have been studying alternative interferometer architectures and beam combination techniques, and evaluating the relevant science and technology tradeoffs. Some of the technical challenges include the development of the cryocooler systems necessary for the telescopes and focal plane array, light and stiff but well-damped truss systems to support the telescopes, and lightweight and coolable optical telescopes. We present results of detailed design studies of the FKSI starting with a design consisting of five one meter diameter telescopes arranged along a truss structure in a linear non-redundant array, cooled to 35 K. A maximum baseline of 20 meters gives a nominal resolution of 26 mas at 5 microns. Using a Fizeau beam combination technique, a simple focal plane camera could be used to obtain both Fourier and spectral data simultaneously for a given orientation of the array. The spacecraft will be rotated to give sufficient Fourier data to reconstruct complex images of a broad range of astrophysical sources. Alternative and simpler three and two telescope designs emphasizing nulling and spectroscopy also have been investigated and will be discussed.

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The X-ray polarization probe mission concept

Bulletin of the American Astronomical Society (2019)

Rachael M. Roettenbacher Ryan Norris Fabien Baron Kenneth G. Carpenter M. J. Creech‐Eakman

The X-ray Polarization Probe is a medium class mission concept to study the accretion flow onto black holes, to use neutron stars as fundamental physics laboratories, and to probe the role of magnetic fields in cosmic particle accelerators. XPP measures linear polarization from 0.2 to 60 keV and provides imaging polarimetry from 2-8 keV.

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Vortex Fiber Nulling for Exoplanet Observations: First Direct Detection of M Dwarf Companions around HIP 21543, HIP 94666, and HIP 50319

arXiv (Cornell University) (2024)

Daniel Echeverri Jerry W. Xuan John D. Monnier Jacques-Robert Delorme Jason Wang

Vortex fiber nulling (VFN) is a technique for detecting and characterizing faint companions at small separations from their host star. A near-infrared ($\sim2.3 \mu$m) VFN demonstrator mode was deployed on the Keck Planet Imager and Characterizer (KPIC) instrument at the Keck Observatory and presented earlier. In this paper, we present the first VFN companion detections. Three targets, HIP 21543 Ab, HIP 94666 Ab, and HIP 50319 B, were detected with host-companion flux ratios between 70 and 430 at and within one diffraction beamwidth ($\lambda/D$). We complement the spectra from KPIC VFN with flux ratio and position measurements from the CHARA Array to validate the VFN results and provide a more complete characterization of the targets. This paper reports the first direct detection of these three M dwarf companions, yielding their first spectra and flux ratios. Our observations provide measurements of bulk properties such as effective temperatures, radial velocities, and v$\sin{i}$, and verify the accuracy of the published orbits. These detections corroborate earlier predictions of the KPIC VFN performance, demonstrating that the instrument mode is ready for science observations.

10.48550/arxiv.2403.17295

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An update on the CHARA array

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE (2016)

Theo A. ten Brummelaar Douglas Gies Harold A. McAlister Stephen T. Ridgway J. Sturmann

The CHARA Array, operated by Georgia State University, is located at Mount Wilson Observatory just north of Los Angeles in California. The CHARA consortium includes many groups, including LIESA in Paris, Observatoire de la Cote d'Azur, the University of Michigan, Sydney University, the Australian National University, the NASA Exoplanet Science Institute, and most recently the University of Exeter. The CHARA Array is a six-element optical/NIR interferometer, and for the time being at least, has the largest operational baselines in the world. In this paper we will give a brief introduction to the array infrastructure with a focus on our Adaptive Optics program, and then discuss current funding as well as opportunities of funding in the near future.

Chara

10.1117/12.2232125

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A novel image reconstruction software for optical/infrared interferometry

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE (2010)

Fabien Baron John D. Monnier Brian Kloppenborg

Imaging large intensity gradients for rapid rotators, complicated spot patterns on rotating RS CVn binaries, and diffuse disk emission around Young Stellar Objects requires advanced imaging methods beyond the current image reconstruction paradigms in optical/infrared interferometry. We report on the ongoing development of SQUEEZE, a flexible software for optical and infrared interferometry capable of simultaneous model-fitting and image reconstruction, and possessing useful new capabilities such as imaging on a spheroid. We treat the problem of the local minimas due to the "missing phase" and explore the use of non-pixel-based reconstructions within the Bayesian evidence and compressed sensing frameworks.

10.1117/12.857364

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Phases in interferometry

New Astronomy Reviews (2007)

John D. Monnier

Astrometry

Closure (psychology)

10.1016/j.newar.2007.06.006

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First Images of R Aquarii and Its Asymmetric H₂O Shell

The Astrophysical Journal (2008)

Sam Ragland H. Le Coroller Eugene Pluzhnik W. D. Cotton W. C. Danchi

We report imaging observations of the symbiotic long-period Mira variable R Aquarii (R Aqr) at near-infrared and radio wavelengths. The near-infrared observations were made with the IOTA imaging interferometer in three narrowband filters centered at 1.51, 1.64, and 1.78 μm, which sample mainly water, continuum, and water features, respectively. Our near-infrared fringe visibility and closure phase data are analyzed using three models. (1) A uniform disk model with wavelength-dependent sizes fails to fit the visibility data, and is inconsistent with the closure phase data. (2) A three-component model, consisting of a Mira star, water shell, and an off-axis point source, provide a good fit to all data. (3) A model generated by a constrained image reconstruction analysis provides more insight, suggesting that the water shell is highly nonuniform, i.e., clumpy. The VLBA observations of SiO masers in the outer molecular envelope show evidence of turbulence, with jetlike features containing velocity gradients.

Visibility

10.1086/529573

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MOPSS. I. Flat Optical Spectra for the Hot Jupiters WASP-4 b and WASP-52b

The Astronomical Journal (2018)

Erin May M. Zhao M. Haidar Emily Rauscher John D. Monnier

We present the first results from MOPSS, The Michigan Optical Planetary Spectra Survey, aimed at creating a database of optical planetary transmission spectra all observed, reduced, and analyzed with a uniform method for the benefit of enabling comparative exoplanet studies. We discuss our methods, and present results for our first two targets observed with the Magellan Baade 6.5 m telescope, one transit of the Hot Jupiter WASP-4b and two transits of the Hot Saturn WASP-52b. Both targets present flat, featureless spectra, corresponding to the presence of aerosols. We find that the cloud decks must begin no lower than 10−4 bar for both planets. For WASP-52b, we also consider the effects of star spots on the transmission spectrum, including unocculted spots and spots on the stellar limb influencing the light curve limb-darkening parameters. We discuss the usefulness of this program in the coming James Webb Space Telescope era.

Hot Jupiter

Spitzer Space Telescope

Eclipse

10.3847/1538-3881/aad4a8

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Status of the Planet Formation Imager (PFI) concept

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE (2016)

Michael Ireland John D. Monnier Stefan Kraus Andrea Isella Stefano Minardi

The Planet Formation Imager (PFI) project aims to image the period of planet assembly directly, resolving structures as small as a giant planet's Hill sphere. These images will be required in order to determine the key mechanisms for planet formation at the time when processes of grain growth, protoplanet assembly, magnetic fields, disk/planet dynamical interactions and complex radiative transfer all interact - making some planetary systems habitable and others inhospitable. We will present the overall vision for the PFI concept, focusing on the key technologies and requirements that are needed to achieve the science goals. Based on these key requirements, we will define a cost envelope range for the design and highlight where the largest uncertainties lie at this conceptual stage.

Envelope (radar)

Protoplanet

10.1117/12.2233926

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Imaging the Disk of Zeta Tau Using the CHARA Array

HAL (Le Centre pour la Communication Scientifique Directe) (2009)

Gail Schaefer Douglas R. Gies E. Baines Tabetha S. Boyajian Vincent Coudé Du Foresto

Chara

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