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

Published online by Cambridge University Press:  10 November 2011

Rainer J. Klement ,
Johny Setiawan ,
Thomas Henning ,
Hans-Walter Rix ,
Boyke Rochau ,
Jens Rodmann  and
Tim Schulze-Hartung
Rainer J. Klement
Affiliation:
Max-Planck-Institute for Astronomy Königstuhl 17, D-69121 Heidelberg, Germany email: klement@mpia.de
Johny Setiawan
Affiliation:
Max-Planck-Institute for Astronomy Königstuhl 17, D-69121 Heidelberg, Germany email: klement@mpia.de
Thomas Henning
Affiliation:
Max-Planck-Institute for Astronomy Königstuhl 17, D-69121 Heidelberg, Germany email: klement@mpia.de
Hans-Walter Rix
Affiliation:
Max-Planck-Institute for Astronomy Königstuhl 17, D-69121 Heidelberg, Germany email: klement@mpia.de
Boyke Rochau
Affiliation:
Max-Planck-Institute for Astronomy Königstuhl 17, D-69121 Heidelberg, Germany email: klement@mpia.de
Jens Rodmann
Affiliation:
European Space Agency, Space Environment and Effects Section, ESTEC
Tim Schulze-Hartung
Affiliation:
Max-Planck-Institute for Astronomy Königstuhl 17, D-69121 Heidelberg, Germany email: klement@mpia.de
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Abstract

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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 Mjup 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.

Keywords

galaxy: solar neighborhoodplanetary systems: formationstars: horizontal-branchstars: individual (HIP 13044)techniques: radial velocities
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 6 , Symposium S276: The Astrophysics of Planetary Systems: Formation, Structure, and Dynamical Evolution , October 2010 , pp. 121 - 125
Copyright
Copyright © International Astronomical Union 2011

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