What question did this study set out to answer?

The study aims to report the discovery of a second giant planet orbiting HD 164604 and analyze its orbital characteristics.

March 12, 2026Open Access

HD 164604 c: A Second Giant Planet on a 15 Yr Orbit and Constraints on the Planet–Planet Mutual Inclination*

Key Points

The study aims to report the discovery of a second giant planet orbiting HD 164604 and analyze its orbital characteristics.
Combined high-precision radial velocity data analysis.
Utilized astrometric data from Hipparcos and Gaia.
Refined orbital parameters of the inner planet HD 164604 b.
HD 164604 c has an orbital semi-major axis of approximately 5.55 AU and an eccentricity of 0.19.
The mass of HD 164604 c is estimated to be around 9.5 Jupiter masses.
The orbital parameters of HD 164604 b were refined to an approximate semi-major axis of 1.36 AU.

Abstract

Abstract We report the discovery of a new massive giant planet, HD 164604 c ( a c = 5.55 6 − 0.10 + 0.093 au, e c = 0.19 6 − 0.078 + 0.078 , and m c = 9 . 5 − 1.25 + 1.2 , or 7 . 6 − 1.0 + 1.0 M Jup ), orbiting a K3.5 dwarf, The result is based on the combined analysis of high-precision radial velocity data and astrometry from Hipparcos and the second and third data releases of Gaia. We refine the orbital parameters of the inner planet HD 164604 b to a b = 1.36 2 − 0.012 + 0.012 au, e b = 0.47 9 − 0.021 + 0.027 , and m b = 13 . 2 − 1.5 + 1.8 M Jup (or

HD 164604 c: A Second Giant Planet on a 15 Yr Orbit and Constraints on the Planet–Planet Mutual Inclination*

Key Points

Abstract

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