TOI-3757 b: A Low-density Gas Giant Orbiting a Solar-metallicity M Dwarf

We present the discovery of a new Jovian-sized planet, TOI-3757 b, lowest density planet orbiting an M dwarf (M0V). It orbits solar-metallicity discovered using TESS photometry and confirmed with precise radial velocities (RV) from HPF NEID. With planetary radius $12.0^{+0.4}_{-0.5}$ $R_{\oplus}$ mass $85.3^{+8.8}_{-8.7}$ $M_{\oplus}$, not only does this object add to small sample gas giants ($\sim 10$) around dwarfs, but also, its low ($\rho =$ $0.27^{+0.05}_{-0.04}$ $\textrm{g~cm}^{-3}$) provides opportunity test theories formation. two hypotheses explain density; first, we posit that metallicity stellar host ($\sim$ 0.3 dex lower than median dwarfs hosting giants) could have played role in delayed formation solid core massive enough initiate runaway accretion. Second, eccentricity estimate $0.14 \pm 0.06$ determine it is also plausible for tidal heating at least partially be responsible inflating TOI-3757b b. The large scale height b makes excellent target transmission spectroscopy studies atmospheric escape composition (TSM $\sim$ 190). use perform helium 10830 \AA~ line. Doing this, place upper limit 6.9 \% (with 90\% confidence) on maximum depth absorption metastable transition He \AA, which can help constraint loss rate energy limited regime.