paper

Revised Masses for Low Density Planets Orbiting the Disordered M-dwarf System TOI-1266

arXiv:2410.20282

Abstract

We present an analysis of 126 new radial velocity measurements from the MAROON-X spectrograph to investigate the TOI-1266 system, which hosts two transiting sub-Neptunes at 10.8 and 18.8 days. We measure masses of $M_{b} = 4.01 \pm 0.55 M_{\oplus}$ for TOI-1266 b and $M_{c} = 2.00 \pm 0.72 M_{\oplus}$ for TOI-1266 c. Our mass measurements agree with existing HARPS-N observations which we combined using a weighted average yielding masses for TOI-1266 b, and c of $M_{b} = 4.10 \pm 0.43 M_{\oplus}$ , $M_{c} = 2.4 \pm 0.54 M_{\oplus}$ respectively. The combined dataset enabled a $\approx 30%$ improvement in mass precision. With bulk densities of $I ¨ _{b}$ = 1.25 $\pm$ 0.36 g cm $^{- 3}$ and $I ¨ _{c}$ = 1.36 $\pm$ 0.31 g cm $^{- 3}$ , the planets are among the lowest density sub-Neptunes orbiting an M dwarf. They are both consistent with rocky cores surrounded by hydrogen helium envelopes. TOI-1266 c may also be consistent with a water-rich composition, but we disfavor that interpretation from an Occam's razor perspective.

8 pages, 6 figures