TESS Discovery of Twin Planets near 2:1 Resonance around Early M Dwarf TOI 4342

With data from the Transiting Exoplanet Survey Satellite (TESS), we showcase improvements to the MIT Quick Look Pipeline (QLP) through the discovery and validation of a multiplanet system around M dwarf TOI 4342 ( T _mag = 11.032, M _⋆ = 0.63 M _⊙ , R _⋆ = 0.60 R _⊙ , T _eff = 3900 K, d = 61.54 pc). With updates to QLP, including a new multiplanet search, as well as faster cadence data from TESS’s First Extended Mission, we discovered two sub-Neptunes ( ${R}_{b}={2.266}_{-0.038}^{+0.038}$ R _⊕ and ${R}_{c}={2.415}_{-0.040}^{+0.043}$ R _⊕ ; P _b = 5.538 days and P _c = 10.689 days) and validated them with ground-based photometry, spectra, and speckle imaging. Both planets notably have high transmission spectroscopy metrics of 36 and 32, making TOI 4342 one of the best systems for comparative atmospheric studies. This system demonstrates how improvements to QLP, along with faster cadence full-frame images, can lead to the discovery of new multiplanet systems.