http://arxiv.org/abs/2203.07178
We present the discovery of a new Jovian-sized planet, TOI-3757 b, the lowest density planet orbiting an M dwarf (M0V). It orbits a solar-metallicity M dwarf discovered using TESS photometry and confirmed with precise radial velocities (RV) from HPF and NEID. With a planetary radius of \plradius{} \earthradius{} and mass of \plmass{} \earthmass{}, not only does this object add to the small sample of gas giants ($\sim 10$) around M dwarfs, but also, its low density ($\rho =$ 0.27$^{+0.05}_{-0.04}$ \gcmcubed{}) provides an opportunity to test theories of planet formation. We present two hypotheses to explain its low density; first, we posit that the low metallicity of its stellar host ($\sim$ 0.3 dex lower than the median metallicity of M dwarfs hosting gas giants) could have played a role in the delayed formation of a solid core massive enough to initiate runaway accretion. Second, we use our eccentricity estimate of $0.14 \pm 0.06$ to estimate the significance of tidal heating for inflating the radius of TOI-3757 b. The low density and large scale height of TOI-3757 b makes it an excellent target for transmission spectroscopy studies of atmospheric escape and composition (TSM $\sim$ 190). We use HPF to perform transmission spectroscopy of TOI-3757 b using the helium line. Doing this, we place an upper limit of 6.9 \% (with 90\% confidence) on the maximum depth of the absorption from the metastable transition of He at $\sim$ 10830 \AA.
S. Kanodia, J. Libby-Roberts, C. Canas, et. al.
Tue, 15 Mar 22
75/108
Comments: Submitted to AAS journals