A warm Sub-Neptune transiting the M3 dwarf TOI 1696

We present the discovery of a warm sub-Neptune around the M dwarf TIC 470381900 (TOI-1696), with a radius of 3.0 ± 0.2 Rearth and an orbital period of 2.5 days, using a combination of TESS and follow-up data. Simultaneous multi-band transit photometry from MuSCAT3 confirms the signal is achromatic and on-target, validating its planetary nature and refining the orbital ephemeris. High-resolution imaging with adaptive optics using Subaru/IRD and Gemini/’Alopeke shows no suspicious companion stars around the star. High-resolution spectroscopy from the Subaru / IRD rules out most spectroscopic binary scenarios. The expected planetary mass is 8-14 Mearth, corresponding to a radial velocity semi-amplitude 9-16 m/s. At J=12.2 mag, it is a promising target for atmospheric characterization with JWST, as well as potentially for mass measurement with NIR spectrographs.