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Bergsten, G.J.; Pascucci, I.; Hardegree-Ullman, K.K.; Fernandes, R.B.; Christiansen, J.L.; Mulders, G.D. |
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Title |
No Evidence for More Earth-sized Planets in the Habitable Zone of Kepler's M versus FGK Stars |
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2023 |
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Astronomical Journal |
Abbreviated Journal |
Astron. J. |
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166 |
Issue |
6 |
Pages  |
234 |
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Keywords |
MAIN-SEQUENCE STARS; LOW-MASS STARS; M DWARFS; OCCURRENCE RATES; STELLAR-MASS; TERRESTRIAL PLANETS; GAIA DR2; CANDIDATES; SAMPLE; RELIABILITY |
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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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0004-6256 |
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WOS:001103102000001 |
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UAI @ alexi.delcanto @ |
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1925 |
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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. |
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Title |
Using Photometrically Derived Properties of Young Stars to Refine TESS's Transiting Young Planet Survey Completeness |
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Year |
2023 |
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Astronomical Journal |
Abbreviated Journal |
Astron. J. |
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166 |
Issue |
4 |
Pages |
175 |
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Keywords |
POWERED MASS-LOSS; RADIUS DISTRIBUTION; VALLEY |
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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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0004-6256 |
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WOS:001080623800001 |
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UAI @ alexi.delcanto @ |
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1910 |
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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. |
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Title |
pterodactyls: A Tool to Uniformly Search and Vet for Young Transiting Planets in TESS Primary Mission Photometry |
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2022 |
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Astronomical Journal |
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Astron. J. |
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164 |
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3 |
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78 |
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POWERED MASS-LOSS; ZODIACAL EXOPLANETS; RADIUS DISTRIBUTION; DWARF; HUNT; STAR; FREQUENCY; EFFICIENT; KEPLER; SYSTEM |
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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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0004-6256 |
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WOS:000835823800001 |
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UAI @ alexi.delcanto @ |
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1636 |
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