TOI-1259Ab-a gas giant planet with 2.7 per cent deep transits and a bound white dwarf companion

We present TOI-1259Ab, a 1.0R(Jup) gas giant planet transiting a 0.71R(circle dot) K-dwarf on a 3.48d orbit. The system also contains a bound white dwarf companion TOI-1259B with a projected distance of similar to 1600 au from the planet host. Transits are observed in nine TESS sectors and are 2.7 per cent deep - among the deepest known - making TOI-1259Ab a promising target for atmospheric characterization. Our follow-up radial velocity measurements indicate a variability of semiamplitude K = 71 ms(-1), implying a planet mass of 0.44M(Jup). By fitting the spectral energy distribution of the white dwarf, we derive a total age of 4.08(-0.53)(+1.21) Gyr for the system. The K dwarfs light curve reveals rotational variability with a period of 28 d, which implies a gyrochronology age broadly consistent with the white dwarf's total age.

Automated summary

TOI-1259Ab is a gas giant planet orbiting a K-dwarf, with a white dwarf companion in its system. Its deep transits make it a promising target for atmospheric characterization. By analyzing the age of the system through various measurements, there is consistency in the estimated total age.