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Constrain short-period super-Earth occurrence at metallicities −0.75 ≤ [Fe/H] ≤ −1.0

Ascertain whether the occurrence rate of short-period (1–10 day) super-Earths continues to decrease in the host star metallicity interval −0.75 ≤ [Fe/H] ≤ −1.0 and determine its quantitative value, overcoming current limitations by expanding the sample size by approximately a factor of four within that metallicity range to enable constraints relative to Kepler/K2 extrapolations.

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Background

The authors detect no super-Earth candidates in the −0.75 ≤ [Fe/H] ≤ −1.0 bin and derive only an upper limit due to the limited sample size. They explicitly state that they cannot further constrain the occurrence rate in this bin compared to extrapolations from Kepler/K2.

They specify that determining whether the occurrence rate continues to decline at these metallicities requires increasing the sample size by roughly fourfold, indicating a concrete unresolved question tied to available data volume.

References

However, given the limited sample size of 20,148 stars within this bin, we cannot further constrain super-Earth occurrence rate compared to Kepler and K2 extrapolations (Figure \ref{fig:occur}). To determine whether in super-Earth occurrence rate would continue to decrease in the [$-0.75$,$-1.0$] bin would require a sample $\sim$ 4 times larger within that metallicity range based on our detection efficiency.

— The First Evidence of a Host Star Metallicity Cut-off In The Formation of Super-Earth Planets (2407.13821 - Boley et al., 18 Jul 2024) in Section 5 (Results)