{"id":{"repo_id":"cambridge","oai_identifier":"oai:www.repository.cam.ac.uk:1810/370612"},"canonical_url":"https://search.dev.ndltd.org/etd/cambridge/oai:www.repository.cam.ac.uk:1810/370612","repository":{"repo_id":"cambridge","name":"Cambridge University","base_url":"https://api.repository.cam.ac.uk/server/oai/request"},"display":{"title":"Discovery and Characterisation of Long-Period Exoplanets with TESS and CHEOPS","abstract":"In this thesis, I present my work on the discovery and characterisation of long-period transiting exoplanets. Detecting exoplanets via the transit method is inherently biased towards short-period planets. Due to the nature of its observing strategy, the Transiting Exoplanet Survey Satellite (TESS) is particularly susceptible to this detection bias. To increase the number of long-period planets, I use TESS ‘duotransits’ — planet candidates with two observed transits separated by a large gap, typically two years. From the two non-consecutive transits the orbital period is unknown, but there exists a discrete set of allowed period aliases. With the CHaracterising ExOPlanet Satellite (CHEOPS), I perform targeted follow-up of TESS duotransits to determine their true periods and confirm them as long-period planets. I begin by describing the specialised pipeline that I created to discover TESS duotransits. My pipeline reads in TESS lightcurves, detrends them using a time-windowed sliding mean, runs a box least squares (BLS) transit search and outputs duotransit candidates. The process was optimised to discover duotransits suitable for CHEOPS follow-up by using injection-recovery tests and selecting BLS parameters based on typical duotransit properties. After running my pipeline on ∼ 40,000 stars, I discovered five duotransit systems that have since been observed by CHEOPS: HD 5806, TOI-5678, TIC 182992572, TIC 130843507 and HD 185619. For the four that have had their orbital period confirmed so far, I performed a joint TESS and CHEOPS analysis to derive each planet’s properties. I also present the TESS and CHEOPS discovery of two warm sub-Neptunes transiting the bright K-dwarf HD 15906, as reported in a publication which I led. In total, I contributed to the discovery of 19 long-period planets as a core member of the CHEOPS Duotransit Program. All of these new discoveries have orbital periods longer than 20 days, radii smaller than 5 R<sub>⊕</sub> and host stars brighter than a Gaia magnitude of 12. These small planets on long-period orbits around bright stars are amenable to detailed characterisation studies, for example radial velocity follow-up to measure their masses or transmission spectroscopy to probe their atmospheres. That makes them particularly valuable for understanding how exoplanet properties change as a function of stellar irradiation and improving our understanding of planet formation and evolution.","abstract_html":"In this thesis, I present my work on the discovery and characterisation of long-period transiting exoplanets. Detecting exoplanets via the transit method is inherently biased towards short-period planets. Due to the nature of its observing strategy, the Transiting Exoplanet Survey Satellite (TESS) is particularly susceptible to this detection bias. To increase the number of long-period planets, I use TESS ‘duotransits’ — planet candidates with two observed transits separated by a large gap, typically two years. From the two non-consecutive transits the orbital period is unknown, but there exists a discrete set of allowed period aliases. With the CHaracterising ExOPlanet Satellite (CHEOPS), I perform targeted follow-up of TESS duotransits to determine their true periods and confirm them as long-period planets. I begin by describing the specialised pipeline that I created to discover TESS duotransits. My pipeline reads in TESS lightcurves, detrends them using a time-windowed sliding mean, runs a box least squares (BLS) transit search and outputs duotransit candidates. The process was optimised to discover duotransits suitable for CHEOPS follow-up by using injection-recovery tests and selecting BLS parameters based on typical duotransit properties. After running my pipeline on ∼ 40,000 stars, I discovered five duotransit systems that have since been observed by CHEOPS: HD 5806, TOI-5678, TIC 182992572, TIC 130843507 and HD 185619. For the four that have had their orbital period confirmed so far, I performed a joint TESS and CHEOPS analysis to derive each planet’s properties. I also present the TESS and CHEOPS discovery of two warm sub-Neptunes transiting the bright K-dwarf HD 15906, as reported in a publication which I led. In total, I contributed to the discovery of 19 long-period planets as a core member of the CHEOPS Duotransit Program. All of these new discoveries have orbital periods longer than 20 days, radii smaller than 5 R&lt;sub&gt;⊕&lt;/sub&gt; and host stars brighter than a Gaia magnitude of 12. These small planets on long-period orbits around bright stars are amenable to detailed characterisation studies, for example radial velocity follow-up to measure their masses or transmission spectroscopy to probe their atmospheres. That makes them particularly valuable for understanding how exoplanet properties change as a function of stellar irradiation and improving our understanding of planet formation and evolution.","abstract_has_math":false,"creators":["Tuson, Amy"],"institution":"University of Cambridge","degree_name":"Doctor of Philosophy (PhD)","degree_level":"Doctoral","degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":["Queloz, Didier"],"committee_chairs":[],"committee_members":[],"year":2023,"date_issued":"2023-12-29","date_published":"2023-12-29","updated_at":"2026-07-22T22:24:21Z","subjects":["Astronomy","Exoplanets","Photometry"],"languages":["eng"],"rights":[],"rights_urls":["https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/c90ad804-2746-4194-be37-15534ff2c411/download","https://creativecommons.org/licenses/by/4.0/"],"identifier_entries":[]},"links":{"outbound_url":"https://doi.org/10.17863/CAM.109981","outbound_label":"DOI","outbound_source":"dc:identifier.doi"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.advisor","label":"Advisor","values":["Queloz, Didier"]},{"key":"dc:creator","label":"Author","values":["Tuson, Amy"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.issued","label":"Date","values":["2023-12-29"]},{"key":"dc:publisher.institution","label":"Dc Publisher Institution","values":["University of Cambridge"]},{"key":"dc:relation.isreferencedby.uri","label":"Dc Relation Isreferencedby URI","values":["https://www.repository.cam.ac.uk/handle/1810/370612"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]},{"key":"dc:type.qualificationlevel","label":"Dc Type Qualificationlevel","values":["Doctoral"]},{"key":"dc:type.qualificationname","label":"Dc Type Qualificationname","values":["Doctor of Philosophy (PhD)"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Astronomy","Exoplanets","Photometry"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["eng"]},{"key":"dc:rights","label":"Dc Rights","values":["https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/c90ad804-2746-4194-be37-15534ff2c411/download","https://creativecommons.org/licenses/by/4.0/"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.doi","label":"DOI","values":["https://doi.org/10.17863/CAM.109981"]},{"key":"dc:identifier.uri","label":"Identifier URI","values":["https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/4088c135-f338-4c24-83a8-1d972740edc4/download"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["In this thesis, I present my work on the discovery and characterisation of long-period transiting exoplanets. Detecting exoplanets via the transit method is inherently biased towards short-period planets. Due to the nature of its observing strategy, the Transiting Exoplanet Survey Satellite (TESS) is particularly susceptible to this detection bias. To increase the number of long-period planets, I use TESS ‘duotransits’ — planet candidates with two observed transits separated by a large gap, typically two years. From the two non-consecutive transits the orbital period is unknown, but there exists a discrete set of allowed period aliases. With the CHaracterising ExOPlanet Satellite (CHEOPS), I perform targeted follow-up of TESS duotransits to determine their true periods and confirm them as long-period planets. I begin by describing the specialised pipeline that I created to discover TESS duotransits. My pipeline reads in TESS lightcurves, detrends them using a time-windowed sliding mean, runs a box least squares (BLS) transit search and outputs duotransit candidates. The process was optimised to discover duotransits suitable for CHEOPS follow-up by using injection-recovery tests and selecting BLS parameters based on typical duotransit properties. After running my pipeline on ∼ 40,000 stars, I discovered five duotransit systems that have since been observed by CHEOPS: HD 5806, TOI-5678, TIC 182992572, TIC 130843507 and HD 185619. For the four that have had their orbital period confirmed so far, I performed a joint TESS and CHEOPS analysis to derive each planet’s properties. I also present the TESS and CHEOPS discovery of two warm sub-Neptunes transiting the bright K-dwarf HD 15906, as reported in a publication which I led. In total, I contributed to the discovery of 19 long-period planets as a core member of the CHEOPS Duotransit Program. All of these new discoveries have orbital periods longer than 20 days, radii smaller than 5 R<sub>⊕</sub> and host stars brighter than a Gaia magnitude of 12. These small planets on long-period orbits around bright stars are amenable to detailed characterisation studies, for example radial velocity follow-up to measure their masses or transmission spectroscopy to probe their atmospheres. That makes them particularly valuable for understanding how exoplanet properties change as a function of stellar irradiation and improving our understanding of planet formation and evolution."]},{"key":"dc:format.checksum.md5","label":"Dc Format Checksum Md5","values":["611db5219ba68d73a16c353e1e0496bb","87eda9de84448d1f82354d60eee3eb5f"]},{"key":"dc:title","label":"Title","values":["Discovery and Characterisation of Long-Period Exoplanets with TESS and CHEOPS"]}]}],"canonical_facts":{"dc:contributor.advisor":["Queloz, Didier"],"dc:creator":["Tuson, Amy"],"dc:date.issued":["2023-12-29"],"dc:description.abstract":["In this thesis, I present my work on the discovery and characterisation of long-period transiting exoplanets. 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The process was optimised to discover duotransits suitable for CHEOPS follow-up by using injection-recovery tests and selecting BLS parameters based on typical duotransit properties. After running my pipeline on ∼ 40,000 stars, I discovered five duotransit systems that have since been observed by CHEOPS: HD 5806, TOI-5678, TIC 182992572, TIC 130843507 and HD 185619. For the four that have had their orbital period confirmed so far, I performed a joint TESS and CHEOPS analysis to derive each planet’s properties. I also present the TESS and CHEOPS discovery of two warm sub-Neptunes transiting the bright K-dwarf HD 15906, as reported in a publication which I led. In total, I contributed to the discovery of 19 long-period planets as a core member of the CHEOPS Duotransit Program. All of these new discoveries have orbital periods longer than 20 days, radii smaller than 5 R<sub>⊕</sub> and host stars brighter than a Gaia magnitude of 12. These small planets on long-period orbits around bright stars are amenable to detailed characterisation studies, for example radial velocity follow-up to measure their masses or transmission spectroscopy to probe their atmospheres. 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