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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 |
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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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Eberhardt, J.; Trifonov, T.; Kurster, M.; Stock, S.; Henning, T.; Wollbold, A.; Reffert, S.; Lee, M.H.; Zechmeister, M.; Rodler, F.; Zakhozhay, O.; Heeren, P.; Gandolfi, D.; Barragan, O.; Pinto, M.T.; Wolthoff, V.; Sarkis, P.; Brems, S.S. |
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Title |
Dynamical Architecture of the HD 107148 Planetary System |
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Year |
2022 |
Publication |
Astronomical Journal |
Abbreviated Journal |
Astron. J. |
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163 |
Issue |
5 |
Pages |
198 |
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Keywords |
LOMB-SCARGLE PERIODOGRAM; EXTRA-SOLAR PLANETS; RADIAL-VELOCITIES; ORBITAL SOLUTIONS; CARMENES SEARCH; M DWARFS; COMPANIONS; PRECISION; STARS; EXOPLANETS |
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We present an independent Doppler validation and dynamical orbital analysis of the two-planet system HD 107148, which was recently announced in Rosenthal et al. Our detailed analyses are based on literature HIRES data and newly obtained HARPS and CARMENES radial-velocity (RV) measurements as part of our survey in search for additional planets around single-planet systems. We perform a periodogram analysis of the available HIRES and HARPS precise RVs and stellar activity indicators. We do not find any apparent correlation between the RV measurements and the stellar activity indicators, thus linking the two strong periodicities to a moderately compact multiplanet system. We carry out orbital fitting analysis by testing various one- and two-planet orbital configurations and studying the posterior probability distribution of the fitted parameters. Our results solidify the existence of a Saturn-mass planet (HD 107148b, discovered first) with a period of P (b) similar to 77.2 days and a second, eccentric (e (c) similar to 0.4), Neptune-mass exoplanet (HD 107148c) with an orbital period of P (c) similar to 18.3 days. Finally, we investigate the two-planet system's long-term stability and overall orbital dynamics with the posterior distribution of our preferred orbital configuration. Our N-body stability simulations show that the system is long-term stable and exhibits large secular osculations in eccentricity but in no particular mean motion resonance configuration. The HD 107148 system, consisting of a solar-type main-sequence star with two giant planets in a rare configuration, features a common proper-motion white dwarf companion and is therefore a valuable target for understanding the formation and evolution of planetary systems. |
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0004-6256 |
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WOS:000778725000001 |
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UAI @ alexi.delcanto @ |
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1562 |
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