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    Richard Schwarz

INTRODUCTION

1. Binary star systems
2. Multiple star systems
3. Statistics

Binary star systems

Many extrasolar planets were discovered orbiting around single stars, details are shown in the Extrasolar Planets Encyclopaedia . Nevertheless, in the solar neighbourhood around 70 percent of the main sequence stars are members of binary star and multiple star systems. Therefore, we expect that many more planets may exist in binary systems and in multiple star systems. There are several detection methods for extrasolar planets, the two most common ones are the radial velocity method and the transit method. Some of the planets were found with the space missions, CoRoT (launched 2006) and Kepler (launched 2009), GAIA (2013) and other were found by the help of ground-based observations. In the quest for new exoplanets close, eclipsing binaries are promising candidates because many lies in the discovery space of former and future space missions like e.g. Plato, Cheops, Tess. In general we distinguish three dynamical types of motion for extrasolar planets in binary star systems:

(i) S-Type: A planet orbits one of the two stars.
(ii) P-Type: A planet stays in an orbit around both stars.
(iii) T-Type: A planet may orbit close to one of the equilibrium points L4 and L5.


Figure 1 shows the schemata of the three configurations; published in Schwarz et al. 2011.

The catalogue is introduced in Schwarz et al. 2016. If you use the catalogue or the figures please cite this publication:
New prospects for observing and cataloguing exoplanets in well-detached binaries, Schwarz et al. 2016, MNRAS, 460, 3598. arXiv ADS

Multiple star systems

Beside binary star systems also multiple star systems may harbour exoplanets. The different possibilities for triple star systems are shown in Fig. 2, whereas quadruple star systems are presented in Fig. 3.


Figure 2 presents the scheme of the different dynamical possibilities of exoplanets in triple star systems.


Figure 3 presents the scheme of the different dynamical possibilities of exoplanets in quadruple star systems.

Statistics

1. Star systems:
~45% of solar like stars (F6- K3) with d < 25 pc are multiple star systems (Raghavan et al. 2010)



Single star systems	Double star systems	Multiple star systems	Reference
54%	33%	13%	Tokovinin et al. (2014)


Statistics of solar-type dwarfs were studied by Tokovinin (2014) with a distance-limited sample of 4847 targets.


2. Planetary systems: known exoplanet host stars



Single star systems	Double star systems	Multiple star systems	Reference
77%	20%	3%	Raghavan et al. (2006)
83%	15%	2%	Mugrauer & Neuhäuser (2009)
88%	10%	2%	Roell et al. (2012)
96%	3%	1%	Schwarz & Zechner Oct-2016
95.99%	3.19%	0.82%	last update Guggenberger Sept-2019


The difference to the upper table is because of the observational bias.

Statistics to the number of detected exoplanets.