As of December 11, 2023, there are just over 5555 confirmed exoplanet detections. Of these exoplanets, only around 200 have been spectroscopically characterized. Spectra are crucial since they provide unique insights into the physical and chemical properties of exoplanets, their atmospheres, and their formation history. Few exoplanet spectra have been obtained because the prevailing spectroscopic techniques, transit spectroscopy and direct imaging, access different physical separations around a star and leave a gap in coverage from about 1 to 10 AU. This gap coincides with the peak of the giant planet occurrence rate such that there is an important population of exoplanets whose spectra cannot be readily obtained with the prevailing techniques. Interferometry can unlock access to these exoplanets and provide spectra for them.
\r\n\r\nExoplanet interferometry has seen waves of interest in the past. However new developments, such as the first interferometric detections, have stoked a revived interest. Though VLTI/GRAVITY and other multi-aperture, long-baseline instruments currently dominate the field, there is a push to develop simpler interferometric architectures. Cross-aperture techniques are of particular interest as they can be readily implemented on existing and future direct imaging instruments with few-to-no modifications. Such single-telescope interferometers and nullers can reach well-within the inner working angle of conventional coronagraphs, but require significantly less infrastructure and investment than their long-baseline counterparts.
\r\n\r\nThis thesis presents vortex fiber nulling (VFN), a new cross-aperture technique for detecting and spectroscopically characterizing exoplanets at separations less than one diffraction beamwidth (\u227e1 \u03bb/D). VFN utilizes the full collecting area of a telescope to efficiently observe within the inner working angle of conventional coronagraphs. The first chapters of this thesis develop the VFN concept and how it can be readily implemented on existing and future instruments. Subsequent chapters present the laboratory demonstrations used to validate the technique and test its limits. Finally, the last chapters cover the design and deployment of a VFN mode to the KPIC instrument at the Keck Telescope. This includes a glimpse into VFN's capabilities with the first direct detection and spectroscopic characterization of three M dwarf companions previously known only from radial velocity and astrometry. This thesis therefore follows the development of VFN from a concept in 2018 to an operating mode with confirmed detections in 2023.
", "doi": "10.7907/92m5-9p38", "publication_date": "2024", "thesis_type": "phd", "thesis_year": "2024" }, { "id": "thesis:14542", "collection": "thesis", "collection_id": "14542", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:04052022-230213679", "primary_object_url": { "basename": "Thesis_JLLOP_SAYSON_finalv2.pdf", "content": "final", "filesize": 32579824, "license": "other", "mime_type": "application/pdf", "url": "/14542/1/Thesis_JLLOP_SAYSON_finalv2.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "New Methods for the Detection and Characterization of Exoplanets", "author": [ { "family_name": "Llop-Sayson", "given_name": "Jorge Domingo", "orcid": "0000-0002-3414-784X", "clpid": "Llop-Sayson-Jorge-Domingo" } ], "thesis_advisor": [ { "family_name": "Mawet", "given_name": "Dimitri", "orcid": "0000-0002-8895-4735", "clpid": "Mawet-D" } ], "thesis_committee": [ { "family_name": "Howard", "given_name": "Andrew W.", "orcid": "0000-0001-8638-0320", "clpid": "Howard-Andrew-W" }, { "family_name": "Mawet", "given_name": "Dimitri", "orcid": "0000-0002-8895-4735", "clpid": "Mawet-D" }, { "family_name": "Fuller", "given_name": "James", "orcid": "0000-0002-4544-0750", "clpid": "Fuller-J" }, { "family_name": "Jovanovic", "given_name": "Nemanja", "orcid": "0000-0001-5213-6207", "clpid": "Jovanovic-Nemanja" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "Advancements in detection technologies have allowed the discovery of thousands of exoplanets. These discoveries have revolutionized our understanding of the Universe; not only are planets ubiquitous, but the planetary systems they populate are as diverse as the complex processes that govern their formation allow. This thesis compiles several studies on the development and application of exoplanet detection and characterization methods, in particular for direct imaging and spectroscopy. From all the planets discovered to date, only a marginal portion have been imaged. This is due to the limited access of high contrast instruments into the parameter space where most exoplanets habitate. Developments in high contrast are key to reaching a full understanding of the exoplanet population. In particular, direct methods allow for an effective characterization of the atmospheric compositions, making it possible to probe exoplanet atmospheres in search of biosignatures.
\r\n\r\nA sure pathway to enhance exoplanet characterization capabilities is by taking full advantage of synergies between detection methods. In Chapter 2 these synergies are explored in the context of \u03b5 Eridani's elusive companion: three different methods are combined to constrain its mass and orbital parameters. Combining astrometry, radial velocity, and direct imaging data offers a complementarity that enhances the overall constraining power. In Chapter 3, the \u03b1 Centauri system is reviewed regarding the possibility of imaging an exoplanet with the JWST observatory in the infrared. The following chapters deal with technological development for high contrast imaging and spectroscopy instruments. In Chapter 4 a coronagraph design study is presented in which new design tools are discussed and evaluated, demonstrating better coronagraph performance. In this chapter the case study is the Nancy Grace Roman Space Telescope Coronagraph Instrument, in which its heavily obstructed pupil constitutes a huge challenge for coronagraph design. Along the same lines, Chapter 5 presents the technology demonstration of the apodized vortex coronagraph (AVC). The AVC is a coronagraph concept that effectively deals with the telescope pupil discontinuities. Chapters 6 and 7 introduce a novel wavefront sensing and control algorithm for the high contrast concept of a fiber injection unit in the image plane of a coronagraph. A single mode fiber (SMF) is placed in the position of the planet to extract its light and feed it into a spectrograph. Our algorithm leverages the synergies of the coronagraph and the mode selectivity of the SMF to maximize the signal-to-noise ratio of the planet.
", "doi": "10.7907/sxz3-d927", "publication_date": "2022", "thesis_type": "phd", "thesis_year": "2022" } ]