Multiplicity Study of Exoplanet Host Stars


The team | Latest resultsOur current Projects | Our Publications | Student Thesis Work | Press Releases


A key aspect in the diversity of exoplanets is the multiplicity of their host stars.

As described by theories stellar companions of exoplanet host stars can significantly influence the formation process of planets around these stars as well as the long-term evolution of their orbits. On the one hand, in close binary systems, planet formation and long-term stable orbits of planets are restricted to the close vicinity (only a few astronomical units) around the host stars. On the other hand, in wide binary systems, the orbital evolution of the star system itself, for example under the influence of galactic tides or perturbations from other passing stars, can significantly affect the orbits of exoplanets around their host stars.

How planets form and evolve in multiple star systems is a very important question in modern astrophysics, since a large fraction of the stars in our galaxy are members of binary or even higher order multiple star systems. Furthermore, the efficiency of planet formation in these systems also affects the total number of planets in the Milky Way.

In order to detect such stellar systems with exoplanets, we have initiated several surveys to search for stellar companions of exoplanet host stars, using either seeing-limited, lucky-, or high-contrast adaptive optics imaging, as well as data releases of the European Space Agency (ESA) Gaia mission. With these different surveys, we are able to cover the entire detection space for possible stellar companions around the exoplanet host stars and can thus accurately determine the multiplicity rate of these stars, and characterize the properties of their companions. Eventually, our efforts will allow us to determine the true impact of stellar multiplicity on planet formation and evolution.

Latest Results:

Detection of White Dwarf Companions of (potential) Exoplanet Host Stars

Left and middle Figure: VIRCAM/VISTA Ks-band images of TOI 2486, and CTOI 161478895. The intrinsic faintness of the white dwarf companions TOI 2486 C and CTOI 161478895 A in the near infrared spectral range is clearly visible in these images.

Right Figure: A (RGB)-color-composite image of TOI 388 (alias WASP-71) with its white dwarf companion TOI 388 B, made of y-, i-, and g-band images, taken by Pan-STARRS.

Reference: Mugrauer, M., Zander, J., & Michel, K.-U. (2022) "Gaia Search for stellar Companions of TESS Objects of Interest III" AN, in press

 Follow-up Observations of the Exoplanet host Binary System g Cep 

Figure.: AstraLux i'-band images of the exoplanet host star g Cep A, and its close stellar companion g Cep B (marked with a white arrow in each image), taken between 2014 and 2020. The AstraLux astrometry is used to obtain an accurate orbital solution for this binary star system and to determine its system parameters.

Reference: Mugrauer, M., Schlagenhauf, S., Buder, S., Ginski, C., Fernández, M., (2022) "Follow-up observations of the binary system g Cep" AN, 343, e224014

The team

Principle Investigator:

Team Members:

  • Christian Adam (Centro de Astronomía de la Universidad de Antofagasta)
  • Lara Dürrenberg (FSU Jena)

  • Matilde Fernández Hernández (IAA-CSIC)

  • Christian Ginski (Anton Pannekoek Institute for Astronomy)

  • Ann-Kathrin Kollak (AIU Jena)
  • Kai-Uwe Michel (AIU Jena)
  • Ralph Neuhäuser (AIU Jena)

  • Johanna Rück (AIU Jena)
  • Saskia Schlagenhauf (AIU Jena)

  • Nikolaus Vogt (Universidad de Valparaíso)
  • Jule Zander (AIU Jena)

Former Team Members:

  • Sven Buder
  • Therese Heyne

  • Tsevi Mazeh
  • Friedemann Reum

  • Tristan Röll

  • Martin Seeliger

  • Andreas Seifahrt

Our current Projects

  • Long-term Multiplicity Survey of northern Exoplanet host Stars with the Lucky-Imager AstraLux at CAHA/2.2m (started in 2008)

    → for results see publications below
  • Long-term Multiplicity Survey of southern Exoplanet host Stars using the extreme Adaptive Optics SPHERE/VLT (started in 2016)

    → for results see publications below
  • Multiplicity Study of Exoplanet Hosts using Data of the ESA-Gaia mission (started in 2018)

    → for results see publications below & VizieR catalogues of detected companions (Link1, Link2)

  • ESA-Gaia Search for stellar companions of TESS Objects of Interest (started in 2020)

    → for results see publications below & VizieR catalogues of detected companions (Link1, Link2, Link3) & Our online image library of detected companions

Our Publications

Student Thesis Work

  • Lara Dürrenberg: "TBA"
  • Ann-Kathrin Kollak: "Suche nach stellaren Begleitern von (C)TOIs"
  • Kai-Uwe Michel: "Search for (sub)stellar Companions of Exoplanet Hosts by using Data from the ESA-Gaia mission"
  • Johanna Rück: "Suche nach stellaren Begleitern potentieller Planeten-Muttersterne"
  • Saskia Schlagenhauf: "AstraLux Lucky-Imaging Observations of Exoplanet host Stars

  • Jule Zander: "ESA-Gaia Search for stellar Companions of TESS Objects of Interest"

Press Releases

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