HD 1397b: A Transiting Warm Giant Planet Orbiting A V = 7.8 mag Subgiant Star Discovered by TESS
Abstract
We report the discovery of a transiting planet first identified as a candidate in Sector 1 of the Transiting Exoplanet Survey Satellite (TESS), and then confirmed with precision radial velocities. HD 1397b has a mass of {M}{{P}} ={0.367}-0.023+0.022 {M}{{J}}, a radius of {R}{{P}}={1.023}-0.013+0.013 {R}{{J}}, and orbits its bright host star (V = 7.8 mag) with an orbital period of 11.5366+/- 0.0003 d on a moderately eccentric orbit (e={0.216}-0.026+0.027). With a mass of {M}\star ={1.257}-0.029+0.029 {M}⊙ , a radius of {R}\star ={2.341}-0.019+0.022 {R}⊙ , and an age of 4.46+/- 0.25 Gyr, the solar-metallicity host star has already departed from the main sequence. We find evidence in the radial velocity measurements of a secondary signal with a longer period. We attribute it to the rotational modulation of stellar activity, but a long-term radial velocity monitoring would be necessary to discard if this signal is produced by a second planet in the system. The HD 1397 system is among the brightest ones currently known to host a transiting planet, which will make it possible to perform detailed follow-up observations in order to characterize the properties of giant planets orbiting evolved stars.
- Publication:
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The Astronomical Journal
- Pub Date:
- July 2019
- DOI:
- arXiv:
- arXiv:1811.02156
- Bibcode:
- 2019AJ....158...45B
- Keywords:
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- planetary systems;
- planets and satellites: detection;
- planets and satellites: gaseous planets;
- Astrophysics - Earth and Planetary Astrophysics;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- 15 pages, submitted to AJ