Stars Would Remember a Recent Gravitational Transition: Testing G-step Resolutions of the Hubble Tension with Red Dwarfs

Abstract

We test the hypothesis that Newton's gravitational constant underwent a rapid transition approximately $73$-$130\mathrm{Myr}$ ago, as proposed in some resolutions of the Hubble tension. Fully convective red dwarf stars with masses below $\sim 0.35M_{\odot }$ have thermal timescales comparable to the proposed transition look-back times, so an appreciable present-day memory can remain. We show that a rapid step in $G$ induces measurable changes in their radii and confront these predictions with mass-radius measurements of eight red dwarfs in detached eclipsing binaries. We find that the $G$-step models proposed to resolve the Hubble tension, corresponding to a $4\%$ change in $G$ at a look-back time of $73\mathrm{Myr}$ and an $11\%$ change at $130\mathrm{Myr}$, are excluded at significances of $3.1\sigma$ and $4.0\sigma$, respectively.

arXiv comment9 pages, three figures, one table