The visitor from an ancient galaxy: A planetary companion around an old, metal-poor red horizontal branch star

Rainer J. Klement; Johny Setiawan; Thomas Henning; Hans-Walter Rix; Boyke Rochau; Jens Rodmann; Tim Schulze-Hartung; MPIA Heidelberg; ESTEC

doi:10.1017/s1743921311020059

arXiv · 1011.4938

The visitor from an ancient galaxy: A planetary companion around an old, metal-poor red horizontal branch star

Rainer J. Klement·Johny Setiawan·Thomas Henning·Hans-Walter Rix·Boyke Rochau·Jens Rodmann·Tim Schulze-Hartung·MPIA Heidelberg·ESTEC

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Abstract

We report the detection of a planetary companion around HIP 13044, a metal-poor red horizontal branch star belonging to a stellar halo stream that results from the disruption of an ancient Milky Way satellite galaxy. The detection is based on radial velocity observations with FEROS at the 2.2-m MPG/ESO telescope. The periodic radial velocity variation of P=16.2 days can be distinguished from the periods of the stellar activity indicators. We computed a minimum planetary mass of 1.25 Jupiter masses and an orbital semimajor axis of 0.116 AU for the planet. This discovery is unique in three aspects: First, it is the first planet detection around a star with a metallicity much lower than few percent of the solar value; second, the planet host star resides in a stellar evolutionary stage that is still unexplored in the exoplanet surveys; third, the planetary system HIP 13044 most likely has an extragalactic origin in a disrupted former satellite of the Milky Way.

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Rainer J. Klement, Johny Setiawan, Thomas Henning, Hans-Walter Rix, Boyke Rochau, Jens Rodmann, Tim Schulze-Hartung, MPIA Heidelberg, ESTEC. 2010-11-22. The visitor from an ancient galaxy: A planetary companion around an old, metal-poor red horizontal branch star. https://doi.org/10.1017/s1743921311020059

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