We report the discovery of GJ 1252 b , a planet with a radius of 1.193 \pm 0.074 R _ { \earth } and an orbital period of 0.52 days around an M3-type star ( 0.381 \pm 0.019 M _ { \sun } , 0.391 \pm 0.020 R _ { \sun } ) located 20.4 pc away .
We use TESS data , ground-based photometry and spectroscopy , Gaia astrometry , and high angular resolution imaging to show that the transit signal seen in the TESS data must originate from a transiting planet .
We do so by ruling out all false positive scenarios that attempt to explain the transit signal as originating from an eclipsing stellar binary .
Precise Doppler monitoring also leads to a tentative mass measurement of 2.09 \pm 0.56 M _ { \earth } .
The host star proximity , brightness ( V = 12.19 mag , K = 7.92 mag ) , low stellar activity , and the system ’ s short orbital period make this planet an attractive target for detailed characterization .