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Author (up) Bergsten, G.J.; Pascucci, I.; Hardegree-Ullman, K.K.; Fernandes, R.B.; Christiansen, J.L.; Mulders, G.D.
Title No Evidence for More Earth-sized Planets in the Habitable Zone of Kepler's M versus FGK Stars Type
Year 2023 Publication Astronomical Journal Abbreviated Journal Astron. J.
Volume 166 Issue 6 Pages 234
Keywords MAIN-SEQUENCE STARS; LOW-MASS STARS; M DWARFS; OCCURRENCE RATES; STELLAR-MASS; TERRESTRIAL PLANETS; GAIA DR2; CANDIDATES; SAMPLE; RELIABILITY
Abstract Reliable detections of Earth-sized planets in the habitable zone remain elusive in the Kepler sample, even for M dwarfs. The Kepler sample was once thought to contain a considerable number of M-dwarf stars ( T-eff < 4000 K), which hosted enough Earth-sized ([0.5, 1.5] R-circle plus) planets to estimate their occurrence rate (eta(circle plus)) in the habitable zone. However, updated stellar properties from Gaia have shifted many Kepler stars to earlier spectral type classifications, with most stars (and their planets) now measured to be larger and hotter than previously believed. Today, only one partially reliable Earth-sized candidate remains in the optimistic habitable zone, and zero in the conservative zone. Here we performed a new investigation of Kepler's Earth-sized planets orbiting M-dwarf stars, using occurrence rate models with considerations of updated parameters and candidate reliability. Extrapolating our models to low instellations, we found an occurrence rate of eta(circle plus) = 8.58( – 8.22 )(+ 17.94) % for the conservative habitable zone (and 14.22 (- 12.71) (+ 24.96 )% for the optimistic one), consistent with previous works when considering the large uncertainties. Comparing these estimates to those from similarly comprehensive studies of Sun-like stars, we found that the current Kepler sample does not offer evidence to support an increase in eta(circle plus) from FGK to M stars. While the Kepler sample is too sparse to resolve an occurrence trend between early and mid-to-late M dwarfs for Earth-sized planets, studies including larger planets and/or data from the K2 and TESS missions are well suited to this task.
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Corporate Author Thesis
Publisher Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0004-6256 ISBN Medium
Area Expedition Conference
Notes WOS:001103102000001 Approved
Call Number UAI @ alexi.delcanto @ Serial 1925
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Author (up) Bergsten, G.J.; Pascucci, I.; Mulders, G.D.; Fernandes, R.B.; Koskinen, T.T.
Title The Demographics of Kepler's Earths and Super-Earths into the Habitable Zone Type
Year 2022 Publication Astronomical Journal Abbreviated Journal Astron. J.
Volume 164 Issue 5 Pages 190
Keywords POWERED MASS-LOSS; PLANET OCCURRENCE RATES; RADIUS DISTRIBUTION; RELIABILITY; DEPENDENCE; EXOPLANETS; MISSION; VALLEY; TRENDS
Abstract Understanding the occurrence of Earth-sized planets in the habitable zone of Sun-like stars is essential to the search for Earth analogs. Yet a lack of reliable Kepler detections for such planets has forced many estimates to be derived from the close-in (2 < P-orb < 100 days) population, whose radii may have evolved differently under the effect of atmospheric mass-loss mechanisms. In this work, we compute the intrinsic occurrence rates of close-in super-Earths (similar to 1-2 R-circle plus and sub-Neptunes (similar to 2-3.5 R-circle plus) for FGK stars (0.56-1.63 M-circle dot) as a function of orbital period and find evidence of two regimes: where super-Earths are more abundant at short orbital periods, and where sub-Neptunes are more abundant at longer orbital periods. We fit a parametric model in five equally populated stellar mass bins and find that the orbital period of transition between these two regimes scales with stellar mass, like P-trans proportional to M-*(1.7 +/- 0.2). Ptrans These results suggest a population of former sub-Neptunes contaminating the population of gigayear-old close-in super-Earths, indicative of a population shaped by atmospheric loss. Using our model to constrain the long-period population of intrinsically rocky planets, we estimate an occurrence rate of Gamma(circle plus) = 15(-4)(+6)% for Earth-sized habitable zone planets, and predict that sub-Neptunes may be similar to twice as common as super-Earths in the habitable zone (when normalized over the natural log-orbital period and radius range used). Finally, we discuss our results in the context of future missions searching for habitable zone planets.
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Corporate Author Thesis
Publisher Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0004-6256 ISBN Medium
Area Expedition Conference
Notes WOS:000867413100001 Approved
Call Number UAI @ alexi.delcanto @ Serial 1665
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Author (up) Fernandes, R.B.; Hardegree-Ullman, K.K.; Pascucci, I.; Bergsten, G.J.; Mulders, G.D.; Cunha, K.; Mamajek, E.E.; Pearson, K.A.; Feiden, G.A.; Curtis, J.L.
Title Using Photometrically Derived Properties of Young Stars to Refine TESS's Transiting Young Planet Survey Completeness Type
Year 2023 Publication Astronomical Journal Abbreviated Journal Astron. J.
Volume 166 Issue 4 Pages 175
Keywords POWERED MASS-LOSS; RADIUS DISTRIBUTION; VALLEY
Abstract The demographics of young exoplanets can shed light on their formation and evolution processes. Exoplanet properties are derived from the properties of their host stars. As such, it is important to accurately characterize the host stars since any systematic biases in their derivation can negatively impact the derivation of planetary properties. Here we present a uniform catalog of photometrically derived stellar effective temperatures, luminosities, radii, and masses for 4865 young (<1 Gyr) stars in 31 nearby clusters and moving groups within 200 pc. We compared our photometrically derived properties to a subset of those derived from spectra and found them to be in good agreement. We also investigated the effect of stellar properties on the detection efficiency of transiting short-period young planets with TESS as calculated in Fernandes et al. (2022) and found an overall increase in the detection efficiency when the new photometrically derived properties were taken into account. Most notably, there is a 1.5 x increase in the detection efficiencies for sub-Neptunes/Neptunes (1.8-6 R-circle plus) implying that, for our sample of young stars, better characterization of host star properties can lead to the recovery of more small transiting planets. Our homogeneously derived catalog of updated stellar properties, along with a larger unbiased stellar sample and more detections of young planets, will be a crucial input to the accurate estimation of the occurrence rates of young short-period planets.
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Corporate Author Thesis
Publisher Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0004-6256 ISBN Medium
Area Expedition Conference
Notes WOS:001080623800001 Approved
Call Number UAI @ alexi.delcanto @ Serial 1910
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Author (up) Fernandes, R.B.; Mulders, G.D.; Pascucci, I.; Bergsten, G.J.; Koskinen, T.T.; Hardegree-Ullman, K.K.; Pearson, K.A.; Giacalone, S.; Zink, J.; Ciardi, D.R.; O'Brien, P.
Title pterodactyls: A Tool to Uniformly Search and Vet for Young Transiting Planets in TESS Primary Mission Photometry Type
Year 2022 Publication Astronomical Journal Abbreviated Journal Astron. J.
Volume 164 Issue 3 Pages 78
Keywords POWERED MASS-LOSS; ZODIACAL EXOPLANETS; RADIUS DISTRIBUTION; DWARF; HUNT; STAR; FREQUENCY; EFFICIENT; KEPLER; SYSTEM
Abstract Kepler's short-period exoplanet population has revealed evolutionary features such as the Radius Valley and the Hot Neptune desert that are likely sculpted by atmospheric loss over time. These findings suggest that the primordial planet population is different from the Gyr-old Kepler population, and motivates exoplanet searches around young stars. Here, we present pterodactyls, a data reduction pipeline specifically built to address the challenges in discovering exoplanets around young stars and to work with TESS Primary Mission 30-minute cadence photometry, since most young stars were not preselected TESS two-minute cadence targets. pterodactyls builds on publicly available and tested tools in order to extract, detrend, search, and vet transiting young planet candidates. We search five clusters with known transiting planets: the Tucana-Horologium Association, IC 2602, Upper Centaurus Lupus, Ursa Major, and Pisces-Eridani. We show that pterodactyls recovers seven out of the eight confirmed planets and one out of the two planet candidates, most of which were initially detected in two-minute cadence data. For these clusters, we conduct injection-recovery tests to characterize our detection efficiency, and compute an intrinsic planet occurrence rate of 49% +/- 20% for sub-Neptunes and Neptunes (1.8-6 R (circle plus)) within 12.5 days, which is higher than Kepler's Gyr-old occurrence rates of 6.8% +/- 0.3%. This potentially implies that these planets have shrunk with time due to atmospheric mass loss. However, a proper assessment of the occurrence of transiting young planets will require a larger sample unbiased to planets already detected. As such, pterodactyls will be used in future work to search and vet for planet candidates in nearby clusters and moving groups.
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Corporate Author Thesis
Publisher Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0004-6256 ISBN Medium
Area Expedition Conference
Notes WOS:000835823800001 Approved
Call Number UAI @ alexi.delcanto @ Serial 1636
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Author (up) Mulders, G.D.; Drazkowska, J.; van der Marel, N.; Ciesla, F.J.; Pascucci, I.
Title Why Do M Dwarfs Have More Transiting Planets? Type
Year 2021 Publication Astrophysical Journal Letters Abbreviated Journal Astrophys. J. Lett.
Volume 920 Issue 1 Pages L1
Keywords TERRESTRIAL PLANETS; GRADUAL ACCUMULATION; GIANT PLANETS; EMBRYOS
Abstract We propose a planet formation scenario to explain the elevated occurrence rates of transiting planets around M dwarfs compared to Sun-like stars discovered by Kepler. We use a pebble drift and accretion model to simulate the growth of planet cores inside and outside of the snow line. A smaller pebble size interior to the snow line delays the growth of super-Earths, allowing giant planet cores in the outer disk to form first. When those giant planets reach pebble isolation mass they cut off the flow of pebbles to the inner disk and prevent the formation of close-in super-Earths. We apply this model to stars with masses between 0.1 and 2 M (circle dot) and for a range of initial disk masses. We find that the masses of hot super-Earths and of cold giant planets are anticorrelated. The fraction of our simulations that form hot super-Earths is higher around lower-mass stars and matches the exoplanet occurrence rates from Kepler. The fraction of simulations forming cold giant planets is consistent with the stellar mass dependence from radial-velocity surveys. A key testable prediction of the pebble accretion hypothesis is that the occurrence rates of super-Earths should decrease again for M dwarfs near the substellar boundary like Trappist-1.
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Corporate Author Thesis
Publisher Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 2041-8205 ISBN Medium
Area Expedition Conference
Notes WOS:000703719200001 Approved
Call Number UAI @ alexi.delcanto @ Serial 1478
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Author (up) Mulders, G.D.; Pascucci, I.; Ciesla, F.J.; Fernandes, R.B.
Title The Mass Budgets and Spatial Scales of Exoplanet Systems and Protoplanetary Disks Type
Year 2021 Publication Astrophysical Journal Abbreviated Journal Astrophys. J.
Volume 920 Issue 2 Pages 66
Keywords MINIMUM-MASS; PLANET OCCURRENCE; DEBRIS DISCS; CLASS-II; NEBULA; STAR; MULTIPLICITY; PROJECT
Abstract Planets are born from disks of gas and dust, and observations of protoplanetary disks are used to constrain the initial conditions of planet formation. However, dust mass measurements of Class II disks with ALMA have called into question whether they contain enough solids to build the exoplanets that have been detected to date. In this paper, we calculate the mass and spatial scale of solid material around Sun-like stars probed by transit and radial velocity exoplanet surveys and compare those to the observed dust masses and sizes of Class II disks in the same stellar-mass regime. We show that the apparent mass discrepancy disappears when accounting for observational selection and detection biases. We find a discrepancy only when the planet formation efficiency is below 100%, or if there is a population of undetected exoplanets that significantly contributes to the mass in solids. We identify a positive correlation between the masses of planetary systems and their respective orbital periods, which is consistent with the trend between the masses and the outer radii of Class II dust disks. This implies that, despite a factor 100 difference in spatial scale, the properties of protoplanetary disks seem to be imprinted on the exoplanet population.
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Corporate Author Thesis
Publisher Place of Publication Editor
Language Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0004-637X ISBN Medium
Area 0004-637X Expedition Conference
Notes WOS:000707456200001 Approved
Call Number UAI @ alexi.delcanto @ Serial 1475
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