Scaling K2 VIII: Short-Period Sub-Neptune Occurrence Rates Peak Around Early-Type M Dwarfs

Fuente: arXiv
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Main Authors: Hardegree-Ullman, Kevin K., Bergsten, Galen J., Christiansen, Jessie L., Zink, Jon K., Bhure, Sakhee, Boley, Kiersten M., Fernandes, Rachel B., Giacalone, Steven, Karpoor, Preethi R.
Format: Preprint
Published: 2025
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author Hardegree-Ullman, Kevin K.
Bergsten, Galen J.
Christiansen, Jessie L.
Zink, Jon K.
Bhure, Sakhee
Boley, Kiersten M.
Fernandes, Rachel B.
Giacalone, Steven
Karpoor, Preethi R.
author_facet Hardegree-Ullman, Kevin K.
Bergsten, Galen J.
Christiansen, Jessie L.
Zink, Jon K.
Bhure, Sakhee
Boley, Kiersten M.
Fernandes, Rachel B.
Giacalone, Steven
Karpoor, Preethi R.
contents We uniformly combined data from the NASA Kepler and K2 missions to compute planet occurrence rates across the entire FGK and M dwarf stellar range. The K2 mission, driven by targets selected by guest observers, monitored nine times more M dwarfs than the Kepler mission. Combined, Kepler and K2 observed 130 short-period ($P=1-40$ days) Earth to Neptune-sized candidate planets orbiting M dwarfs. K2 observed 3.5 times more of these planets than Kepler for host stars below 3700 K. Our planet occurrence rates show that short-period sub-Neptunes peak at $3750^{+153}_{-97}$ K and drop for cooler M dwarfs. A peak near this location was predicted by pebble accretion planet formation models and confirmed here by observations for the first time. Super-Earths continue to increase in occurrence toward cooler stars and show no clear evidence of a peak in the host star range considered here (3200 K$-$6900 K). Our observations provide critical input to further refine planet formation models. We strongly recommend further study of mid-to-late M dwarfs with TESS and soon the Nancy Grace Roman Space Telescope and PLATO to identify additional small planet trends.
format Preprint
id arxiv_https___arxiv_org_abs_2508_05734
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Scaling K2 VIII: Short-Period Sub-Neptune Occurrence Rates Peak Around Early-Type M Dwarfs
Hardegree-Ullman, Kevin K.
Bergsten, Galen J.
Christiansen, Jessie L.
Zink, Jon K.
Bhure, Sakhee
Boley, Kiersten M.
Fernandes, Rachel B.
Giacalone, Steven
Karpoor, Preethi R.
Earth and Planetary Astrophysics
Solar and Stellar Astrophysics
We uniformly combined data from the NASA Kepler and K2 missions to compute planet occurrence rates across the entire FGK and M dwarf stellar range. The K2 mission, driven by targets selected by guest observers, monitored nine times more M dwarfs than the Kepler mission. Combined, Kepler and K2 observed 130 short-period ($P=1-40$ days) Earth to Neptune-sized candidate planets orbiting M dwarfs. K2 observed 3.5 times more of these planets than Kepler for host stars below 3700 K. Our planet occurrence rates show that short-period sub-Neptunes peak at $3750^{+153}_{-97}$ K and drop for cooler M dwarfs. A peak near this location was predicted by pebble accretion planet formation models and confirmed here by observations for the first time. Super-Earths continue to increase in occurrence toward cooler stars and show no clear evidence of a peak in the host star range considered here (3200 K$-$6900 K). Our observations provide critical input to further refine planet formation models. We strongly recommend further study of mid-to-late M dwarfs with TESS and soon the Nancy Grace Roman Space Telescope and PLATO to identify additional small planet trends.
title Scaling K2 VIII: Short-Period Sub-Neptune Occurrence Rates Peak Around Early-Type M Dwarfs
topic Earth and Planetary Astrophysics
Solar and Stellar Astrophysics
url https://arxiv.org/abs/2508.05734