Detecting exoplanets through direct imaging at lower angular separations, where more planets are expected to be, is limited by the variability of the stellar point spread function. Integral field spectrographs like OSIRIS at the Keck Observatory can leverage high spectral resolution to search for new planets at smaller separations (< 0.3 arcseconds) by detecting their distinct spectral signature compared to the diffracted starlight. In this thesis, we present the mid-survey results of a search for planets around 23 targets in the Ophiuchus and Taurus star-forming regions.
\r\n\r\nWe use this pathfinder survey with Keck/OSIRIS to demonstrate our technique and compare the final sensitivities to other classical imaging techniques, particularly at separations of 0.05-0.3 arcseconds. We detect an M dwarf companion around HD 148352 at a \u2248 34\u03c3 significance level. We measure this binary star companion to be at an angular separation of roughly $0.11$ milliarcseconds, with a contrast of $0.38\\%$, effective temperature Teff \u2248 3200 K, and radial velocity RV \u2248 12 km/s. We also present other low-significance objects, along with detection maps and sensitivity limits around these 23 targets.
\r\n\r\nWe use our open-source data analysis pipeline, called the Broad Repository for Exoplanet Analysis, Detection, and Spectroscopy (breads), as the framework for this planet search. breads operates on high spectral resolution data from existing and in-development instruments. Our code is based on a forward-modeling framework, which is statistically more accurate than classical cross-correlation techniques. It includes a built-in optimization and analytical marginalization of linear parameters in the forward model, therefore limiting the number of parameters to be explored by the posterior sampling method. We allow users to select forward models, parameters to detect and analyze, and fitting methods like Markov Chain Monte Carlo sampling, grid optimization, and gradient descent. breads provides a flexible framework to retrieve radial velocity, spin, and atmospheric parameters of high-contrast companions. We also describe wavelength and resolution calibration, transmission and spectra calculation, and bad pixel identification techniques.
\r\n\r\nOur work will be applicable to future integral field spectrographs like NIRSpec on the James Webb Space Telescope and other first light instruments on the future Extremely Large Telescopes, which are poised to become the next generation of exoplanet detection facilities.
" }, { "name": "Johnson, Gwendolyn Brook", "degree": "PhD", "year": "2013", "title": "Modeling, Simulation, and Design of Self-Assembling Space Systems: Accurate Collision Detection, Robust Time Integration, and Optimal Control", "advisor": "Ortiz, Michael", "url": "https://resolver.caltech.edu/CaltechTHESIS:09132012-125328533", "creators": [ { "name": { "family": "Johnson", "given": "Gwendolyn Brook" }, "id": "Johnson-G-B", "display_name": "Johnson, Gwendolyn Brook" } ], "advisors": [ { "name": { "family": "Ortiz", "given": "Michael" }, "id": "Ortiz-M", "role": "advisor", "display_name": "Ortiz, Michael" } ], "committee": [ { "name": { "family": "Ravichandran", "given": "Guruswami" }, "id": "Ravichandran-G", "role": "chair", "display_name": "Ravichandran, Guruswami" }, { "name": { "family": "Ortiz", "given": "Michael" }, "id": "Ortiz-M", "role": "member", "display_name": "Ortiz, Michael" }, { "name": { "family": "Leyendecker", "given": "Sigrid" }, "id": "Leyendecker-S", "role": "member", "display_name": "Leyendecker, Sigrid" }, { "name": { "family": "Pellegrino", "given": "Sergio" }, "id": "Pellegrino-S", "role": "member", "display_name": "Pellegrino, Sergio" } ], "option_major": [ "aeronautics" ], "doi": "10.7907/73S0-Y593", "abstract": "Motivated by issues inherent in modeling and designing self-assembling systems (e.g. multiple collisions, collisions between non-smooth bodies, clumping and jamming behaviors, etc.), the goal of this thesis is to develop robust numerical tools that enable ecient and accurate direct simulation of self assembling systems and the application of optimal control methods to this type of system. The systems will be alternately modeled using linear nite elements, rigid bodies, or chains of rigid bodies. To this end, this work begins with development of a linear programming based collision detection algorithm for general convex polyhedral bodies. The resulting linear program has several features which render it extremely useful in determining the force system at the time of contact in numerical collision integrators. With robust collision detection in hand, three related numerical integration methods for dynamics with collisions are treated; a direct potential-based approach, and exact collision integrator in a discrete variational setting, and a decomposition-based algorithm, again in the discrete variational setting. Finally, several control problems are treated in the Discrete Mechanics and Optimal Control{Constrained (DMOCC) framework in which collisions between non-smooth bodies either need to be avoided or explicitly included in the optimal control problem. A globally stable feedback controller and a family of trajectories for spacecraft docking are also developed and tested with an accurate representation of an optimized CubeSat docking system." } ]