Scaling K2. VII. Evidence For a High Occurrence Rate of Hot Sub-Neptunes at Intermediate Ages
The NASA K2 mission obtained high-precision time-series photometry for four young clusters, including the near-twin 600–800 Myr old Praesepe and Hyades clusters. Hot sub-Neptunes are highly prone to mass-loss mechanisms, given their proximity to the host star and the weakly bound gaseous envelopes,...
| Main Authors: | , , , , , , , , |
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| Format: | Article |
| Language: | English |
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IOP Publishing
2023-01-01
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| Series: | The Astronomical Journal |
| Subjects: | |
| Online Access: | https://doi.org/10.3847/1538-3881/acf9f9 |
| _version_ | 1797627489828208640 |
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| author | Jessie L. Christiansen Jon K. Zink Kevin K. Hardegree-Ullman Rachel B. Fernandes Philip F. Hopkins Luisa M. Rebull Kiersten M. Boley Galen J. Bergsten Sakhee Bhure |
| author_facet | Jessie L. Christiansen Jon K. Zink Kevin K. Hardegree-Ullman Rachel B. Fernandes Philip F. Hopkins Luisa M. Rebull Kiersten M. Boley Galen J. Bergsten Sakhee Bhure |
| author_sort | Jessie L. Christiansen |
| collection | DOAJ |
| description | The NASA K2 mission obtained high-precision time-series photometry for four young clusters, including the near-twin 600–800 Myr old Praesepe and Hyades clusters. Hot sub-Neptunes are highly prone to mass-loss mechanisms, given their proximity to the host star and the weakly bound gaseous envelopes, and analyzing this population at young ages can provide strong constraints on planetary evolution models. Using our automated transit detection pipeline, we recover 15 planet candidates across the two clusters, including 10 previously confirmed planets. We find a hot sub-Neptune occurrence rate of 79%–107% for GKM stars in the Praesepe cluster. This is 2.5–3.5 σ higher than the occurrence rate of ${16.54}_{-0.98}^{+1.00}$ % for the same planets orbiting the ∼3–9 Gyr old GKM field stars observed by K2, even after accounting for the slightly supersolar metallicity ([Fe/H] ∼ 0.2 dex) of the Praesepe cluster. We examine the effect of adding ∼100 targets from the Hyades cluster and extending the planet parameter space under examination, and we find similarly high occurrence rates in both cases. The high occurrence rate of young, hot sub-Neptunes could indicate either that these planets are undergoing atmospheric evolution as they age, or that planetary systems that formed when the Galaxy was much younger are substantially different than from today. Under the assumption of the atmospheric mass-loss scenario, a significantly higher occurrence rate of these planets at the intermediate ages of Praesepe and Hyades appears more consistent with the core-powered mass-loss scenario for the origin of the planet radius valley, compared to the photoevaporation scenario. |
| first_indexed | 2024-03-11T10:24:58Z |
| format | Article |
| id | doaj.art-be67bcfe34e448c1b46a0e1c85514704 |
| institution | Directory Open Access Journal |
| issn | 1538-3881 |
| language | English |
| last_indexed | 2024-03-11T10:24:58Z |
| publishDate | 2023-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astronomical Journal |
| spelling | doaj.art-be67bcfe34e448c1b46a0e1c855147042023-11-15T16:58:11ZengIOP PublishingThe Astronomical Journal1538-38812023-01-01166624810.3847/1538-3881/acf9f9Scaling K2. VII. Evidence For a High Occurrence Rate of Hot Sub-Neptunes at Intermediate AgesJessie L. Christiansen0https://orcid.org/0000-0002-8035-4778Jon K. Zink1https://orcid.org/0000-0003-1848-2063Kevin K. Hardegree-Ullman2https://orcid.org/0000-0003-3702-0382Rachel B. Fernandes3https://orcid.org/0000-0002-3853-7327Philip F. Hopkins4https://orcid.org/0000-0003-3729-1684Luisa M. Rebull5https://orcid.org/0000-0001-6381-515XKiersten M. Boley6https://orcid.org/0000-0001-8153-639XGalen J. Bergsten7https://orcid.org/0000-0003-4500-8850Sakhee Bhure8NASA Exoplanet Science Institute , IPAC, MS 100-22, Caltech, 1200 E. California Blvd, Pasadena, CA 91125, USA ; christia@ipac.caltech.eduDepartment of Astronomy, Caltech , 1200 E. California Blvd, Pasadena, CA 91125, USASteward Observatory, The University of Arizona , Tucson, AZ 85721, USADepartment of Astronomy & Astrophysics, Center for Exoplanets and Habitable Worlds, The Pennsylvania State University , University Park, PA 16802, USA; Lunar and Planetary Laboratory, The University of Arizona , Tucson, AZ 85721, USATAPIR , MS 350-17, Caltech, 1200 E. California Blvd, Pasadena, CA 91125, USAInfrared Science Archive (IRSA) , IPAC, MS 100-22, Caltech, 1200 E. California Blvd, Pasadena, CA 91125, USADepartment of Astronomy, The Ohio State University , Columbus, OH 43210, USALunar and Planetary Laboratory, The University of Arizona , Tucson, AZ 85721, USANASA Exoplanet Science Institute , IPAC, MS 100-22, Caltech, 1200 E. California Blvd, Pasadena, CA 91125, USA ; christia@ipac.caltech.eduThe NASA K2 mission obtained high-precision time-series photometry for four young clusters, including the near-twin 600–800 Myr old Praesepe and Hyades clusters. Hot sub-Neptunes are highly prone to mass-loss mechanisms, given their proximity to the host star and the weakly bound gaseous envelopes, and analyzing this population at young ages can provide strong constraints on planetary evolution models. Using our automated transit detection pipeline, we recover 15 planet candidates across the two clusters, including 10 previously confirmed planets. We find a hot sub-Neptune occurrence rate of 79%–107% for GKM stars in the Praesepe cluster. This is 2.5–3.5 σ higher than the occurrence rate of ${16.54}_{-0.98}^{+1.00}$ % for the same planets orbiting the ∼3–9 Gyr old GKM field stars observed by K2, even after accounting for the slightly supersolar metallicity ([Fe/H] ∼ 0.2 dex) of the Praesepe cluster. We examine the effect of adding ∼100 targets from the Hyades cluster and extending the planet parameter space under examination, and we find similarly high occurrence rates in both cases. The high occurrence rate of young, hot sub-Neptunes could indicate either that these planets are undergoing atmospheric evolution as they age, or that planetary systems that formed when the Galaxy was much younger are substantially different than from today. Under the assumption of the atmospheric mass-loss scenario, a significantly higher occurrence rate of these planets at the intermediate ages of Praesepe and Hyades appears more consistent with the core-powered mass-loss scenario for the origin of the planet radius valley, compared to the photoevaporation scenario.https://doi.org/10.3847/1538-3881/acf9f9ExoplanetsExoplanet atmospheric evolution |
| spellingShingle | Jessie L. Christiansen Jon K. Zink Kevin K. Hardegree-Ullman Rachel B. Fernandes Philip F. Hopkins Luisa M. Rebull Kiersten M. Boley Galen J. Bergsten Sakhee Bhure Scaling K2. VII. Evidence For a High Occurrence Rate of Hot Sub-Neptunes at Intermediate Ages The Astronomical Journal Exoplanets Exoplanet atmospheric evolution |
| title | Scaling K2. VII. Evidence For a High Occurrence Rate of Hot Sub-Neptunes at Intermediate Ages |
| title_full | Scaling K2. VII. Evidence For a High Occurrence Rate of Hot Sub-Neptunes at Intermediate Ages |
| title_fullStr | Scaling K2. VII. Evidence For a High Occurrence Rate of Hot Sub-Neptunes at Intermediate Ages |
| title_full_unstemmed | Scaling K2. VII. Evidence For a High Occurrence Rate of Hot Sub-Neptunes at Intermediate Ages |
| title_short | Scaling K2. VII. Evidence For a High Occurrence Rate of Hot Sub-Neptunes at Intermediate Ages |
| title_sort | scaling k2 vii evidence for a high occurrence rate of hot sub neptunes at intermediate ages |
| topic | Exoplanets Exoplanet atmospheric evolution |
| url | https://doi.org/10.3847/1538-3881/acf9f9 |
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