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"Merand A."

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Davidson, J. W., Jr., Horch, E. P., & Majewski, S. R. (2018). Speckle imaging through a coherent fiber bundle. In Tuthill P.G., Creech-Eakman M.J., & Merand A. (Eds.), Proc SPIE Int Soc Opt Eng (Vol. 10701). SPIE. Scopus. https://doi.org/10.1117/12.2323856

Speckle imaging is a well known method to achieve diffraction-limited (DL) imaging from ground-based telescopes. The traditional observing method for speckle has been to observe a single, unresolved, source per telescope pointing over a relatively small field of view (FOV). The need for large DL surveys of targets with high sky density motivates a desire for simultaneous speckle imaging over large FOVs, however it is currently impractical to attain this by covering the entire focal plane with fast readout detectors. An alternative approach is to connect a relatively small number of detector pixels to multiple interesting targets spanning a large FOV through the use of optical fibers, a technique employed in spectroscopy for decades. However, for imaging we require the use of coherent fiber bundles (CFBs). We discuss various design considerations for coherent fiber speckle imaging with an eye toward a multiplexed system using numerous configurable CFBs, and we test its viability with a prototype instrument that uses a single CFB to transport speckle images from the telescope focal plane to a traditionally designed, fast readout speckle camera. Using this device on University of Virginia's Fan Mountain Observatory 40-inch telescope we have for the first time successfully demonstrated speckle imaging through a CFB, using both optical and NIR detectors. Results are presented of DL speckle imaging of well-known close (including subarcsecond) binary stars resolved with this fiber-fed speckle system and compared to both literature results and traditional speckle imaging taken with the same camera directly, with no intervening CFB. © 2018 SPIE.

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Klaucke, P. M., Pellegrino, R. A., Weiss, S. A., & Horch, E. P. (2020). Toward an imaging capability with the Southern Connecticut Stellar Interferometer. In Tuthill P.G., Merand A., & Sallum S. (Eds.), Proc SPIE Int Soc Opt Eng (Vol. 11446). SPIE. Scopus. https://doi.org/10.1117/12.2576346

The Southern Connecticut Stellar Interferometer (SCSI) is an intensity interferometer that is designed to use correlated photon arrival times to determine the geometry of stars. Originally a low-cost, two-telescope instrument that used a 1-pixel single-photon avalanche diode (SPAD) detector at the focal plane of each telescope to record photon events, it is now being upgraded to include a third telescope. This will allow for the simultaneous detection of the photon correlation at three baselines, and thus the ability to map out the two-dimensional geometry of the source much more efficiently than with the two-telescope arrangement. Recent papers in the literature suggest that it may be possible to derive phase information in the Fourier domain from such triple correlations for the brightest stars, potentially giving SCSI an imaging capability. Prior to investigating this possibility, steps must be taken to maximize the observing efficiency of the SCSI. We present here our latest efforts in achieving better pointing, tracking, and collimation with our telescopes, and we discuss our first modeling results of the three-telescope situation in order to understand under what conditions the upgraded SCSI could retrieve imaging information. © COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only.

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Hahne, F. W., Horch, E. P., Van Belle, G. T., Clark, C., Winters, J. G., & Henry, T. J. (2018). Two-color speckle imaging of M-dwarfs with the Discovery Channel telescope. In Tuthill P.G., Creech-Eakman M.J., & Merand A. (Eds.), Proc SPIE Int Soc Opt Eng (Vol. 10701). SPIE. Scopus. https://doi.org/10.1117/12.2314024

Lowell Observatory and Southern Connecticut State University are currently involved in a joint project to determine the stellar multiplicity rates and the fundamental stellar parameters of M dwarf stars using the Differential Speckle Survey Instrument (DSSI) at Lowell's Discovery Channel Telescope (DCT). DSSI observes speckle patterns simultaneously at two separate wavelengths, allowing color measurements of the components of a binary system to be made in a single observation. This paper will describe the initial data gathering process, which began in 2016. Since then, over 1000 stars have been observed. We summarize the analysis on these objects so far, and discuss the relevance of these observations for existing and future space missions such as TESS, JWST, and Gaia. © 2018 SPIE.

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Hess, N. M., Thayer, P. R., Horch, E. P., Davidson, J. W., Jr., Baptista, B. J., Everett, M. E., & Howell, S. B. (2018). Speckle imaging of KOI binary stars with the WIYN telescope. In Tuthill P.G., Creech-Eakman M.J., & Merand A. (Eds.), Proc SPIE Int Soc Opt Eng (Vol. 10701). SPIE. Scopus. https://doi.org/10.1117/12.2313008

Binary star systems where one of the stars is an exoplanet host appear to be more common than expected prior to the Kepler mission. The Kepler mission and subsequent ground-based follow-up work have revealed a number of Kepler Objects of Interest (KOIs) that have nearby stellar companions (within ∼1 arcsec). KOIs with stellar companions and at least one suspected exoplanet were selected for this work. Recent work on these stars has mainly focused on placing the companions on the H-R diagram and inferring if they are likely to be gravitationally bound based on whether their locations are consistent with a common isochrone. However, we have been observing these KOI double stars with speckle imaging over several years and are now in a position to assess whether these systems have components with a common proper motion, and can be seen as physically associated on that basis. We will give sample results of KOI double stars that are in fact common proper motion pairs. We compare our results with estimates of the multiplicity rate of exoplanet hosts from other methods and comment on the use of our data for constraining orbital parameters at this point, particularly the inclination angle. For transit observations, the inclination of the planetary orbit is already known, and the relationship between planetary and stellar orbital planes could have implications for star and planet formation. © 2018 SPIE.

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Clark, C. A., Van Belle, G. T., Horch, E. P., Trilling, D. E., Hartman, Z. D., Collins, M., Von Braun, K., & Gehring, J. (2020). The optomechanical design of the Quad-camera Wavefront-sensing Six-channel Speckle Interferometer (QWSSI). In Tuthill P.G., Merand A., & Sallum S. (Eds.), Proc SPIE Int Soc Opt Eng (Vol. 11446). SPIE. Scopus. https://doi.org/10.1117/12.2563055

The Quad-camera Wavefront-sensing Six-channel Speckle Interferometer (QWSSI) is a new speckle imaging instrument available on the 4.3-m Lowell Discovery Telescope (LDT). QWSSI is built to efficiently make use of collected photons and available detector area. The instrument images on a single Electron Multiplying CCD (EMCCD) at four wavelengths in the optical (577, 658, 808, and 880nm) with 40nm bandpasses. Longward of 1μm, two imaging wavelengths in the NIR are collected at 1150 and 1570nm on two InGaAs cameras with 50nm bandpasses. All remaining non-imaging visible light is then sent into a wavefront EMCCD. All cameras are operated synchronously via concurrent triggering from a timing module. With the simultaneous wavefront sensing, QWSSI characterizes atmospheric aberrations in the wavefront for each speckle frame. This results in additional data that can be utilized during post-processing, enabling advanced techniques such as Multi-Frame Blind Deconvolution. The design philosophy was optimized for an inexpensive, rapid build; virtually all parts were commercial-off-the-shelf (COTS), and custom parts were fabricated or 3D printed on-site. QWSSI's unique build and capabilities represent a new frontier in civilian high-resolution speckle imaging. © COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only.

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