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

TL;DR

TOI-1259Ab is a deep-transit gas giant exoplanet orbiting a K-dwarf, with a white dwarf companion, offering valuable insights into planetary systems with stellar remnants and promising atmospheric study potential.

Contribution

This study reports the discovery and characterization of TOI-1259Ab, a deep-transit gas giant with a white dwarf companion, providing new data on such complex stellar systems.

Findings

Deep 2.7% transits make it ideal for atmospheric studies.

Radial velocity data indicate a planet mass of 0.44 Jupiter masses.

System age estimated at around 4 Gyr from white dwarf and stellar data.

Abstract

We present TOI-1259Ab, a 1.0 Rjup gas giant planet transiting a 0.71 Rsun K-dwarf on a 3.48 day orbit. The system also contains a bound white dwarf companion TOI-1259B with a projected distance of approximately 1600 AU from the planet host. Transits are observed in nine TESS sector 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 m/s, implying a planet mass of 0.44 Mjup. By fitting the spectral energy distribution of the white dwarf we derive a total age of 4.08 (+1.21 -0.53) Gyr for the system. The K-dwarf's light curve reveals a rotational variability with a period of 28 days, which implies a gyrochronology age broadly consistent with the white dwarf's total age.