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Circumbinary Planet Detection with PLATO. WP112510: Hans Deeg (WP leader) Instituto de Astrofísica de Canarias, ES José Manuel Almenara LAM, FR Stefan Dreizler University of Goettingen, DE Rudolf Dvorak Univ. Vienna, AT Francesca Faedi Warwick University, GB Petr Kabath ESO fellow

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Circumbinary planet detection with plato
Circumbinary Planet Detection with PLATO


Hans Deeg (WP leader) Instituto de Astrofísica de Canarias, ES

José Manuel Almenara LAM, FR

Stefan Dreizler University of Goettingen, DE

Rudolf Dvorak Univ. Vienna, AT

Francesca Faedi Warwick University, GB

Petr Kabath ESO fellow

Maciej Konacki Nicolaus Copernicus Astron. Ctr., Torun, PL

Willy Kley Univ. Tübingen, D

Tsevi Mazeh Tel Aviv University, IS

Aviv Ofir University of Göttingen, DE

Jean Schneider Observatoire de Paris, FR


Circumbinary planets
Circumbinary Planets

Planets in orbit around both binary components (P-type orbit)

Spielberg et al, 1977: Planet Tatooine

Backer 1993: Timing of PSR B1620-26: Pulsar-WD binary plus low-mass object only 10-12 yrs later accepted as planet, 2.5Mjup, P=100y (Sigurðsson+03, Backer+ 05, Rasio 05 etc)

MacCabe et al 2003: HST-NICMOS obs of Circumbinary disk of GG Tau


Current status
Current status

  • 14 CBP known in 12 systems

  • All early (<2011) discoveries are on evolved stars; by eclipse timing variations

  • ≥2011: CBPs on MS stars in Kepler data

  • No CBP discovered by radial velocity

ADS, in abstract: CIsource RCUMBINARY and PLANET

Circumbinary AND planet

in abstract

Source: ADS

  • Pierens & Nelson (2007, 2008a,b): series on CBP formation, migration and evolution. Inward drift of protoplanet may stop near binary cavity..

  • Most Kepler CBPs (except 34b, 47c) within few % of critical orbital semi-major axis. apl/ab = 3.1 to 3.6 (Welsh+ 2012; Orosz+ 2012).

  • Pierens & Nelson (2013) on 3 Kepler CBP: Scenario in which a core forms, migrates inward and accretes gas


Circumbinary planet detection
Circumbinary planet detection

  • Several photometric methods:

  • Eclipse timing variations (ETV)

  • Transits

  • ‘Eclipse Echos’

  • No RV discovery, but ongoing TATOOINE Search (Konacki+ 2009)


Cbp t ransit detection
CBP transit detection

  • Transits likely to occur: Planet disks preferentially aligned with binary plane (strong missalingmentimpossible, Bate + 2000)

  • Unique transit signal, low False Alarm prob. Details of transit depend on EB phase.

Kepler 16(AB)b

Kepler 16b

  • Specific detection algorithms needed: (Doyle+ 2000, Ofir+ 09, Kostov+ 13,

  • Removal of binary signal

  • Detection of semi-periodic transits within ‘transit window’ (Doyle+ 2000, Armstrong+ 13)

Doyle + 2011

Kepler38b (Orosz+ 12)

Deeg+ 1998


Detection of 3 rd bodies by eclipse time variations etv
Detection of 3rd bodies by eclipse time variations (ETV)

  • First use: Botsula 1956 for TX Her

  • All ‘pre-Kepler’ CBPs found by ETV

    Amplitude of variation

    of minimum time from light-time variation:

    DTmin~ Mpl MEB-2/3 p2/3

  • Stronger ETVs from planets with mean-motionresonances ≥3:1 (Schwarz+ 11)

  • ETV used to verify transit detec.; set masses

  • Planets found by ETV long-periodic ≥7.5yr


Eclipse echos

eclipse in reflected light from planet

Eclipse Echos

Detection of binary eclipses in planet’s reflected light

Deeg & Doyle 2011


Detectability of CBP in Kepler data from Eclipse Echos

Detectability of 1Rj CPB at inner orbital stability limit in 4yr data of Kepler EBs

Green: Detached

Blue: Semi-detach.

Red: Over-contact

Bold symbols:

Targets for EE search with σdet > 3:

38 Detached

62 Semi-detached

350 Over-contact

σdet~ 10

σdet~ 3

Adapted from Deeg & Doyle 2011; Kepler EBs from Prsa et al. 2011


Etv versus transit detection
ETV versus Transit detection

Example: Cm Dra M4.5/M4.5 binary; MCM DRA = 0.44 Msol6 yrs /1000hr ground obs. for Transits (Deeg+ 1998, Doyle+ 2000)

with 54 eclipses, st0 ≈ 6 sec (Deeg+ 2000)



Deeg+ 2000

Max. a for Transit-discovery given by inclination of binary, assuming coplanar planet

Plato cbp detection
PLATO CBP detection

  • 2410 EBs out of Kepler sample of ~160k stars -> ~1.5% are Ebs

  • (Kepler Eclipsing Binary Catalogue V3 (Villanova U.; Kirk+ 13 in rep))

  • 6 CBP detected, all with transits, rather long periods 50-303d

  • Absence of CBP on shorter-periodic binaries?

  • Several detection efforts to find shallow-transit CBPs ongoing

  • Detection effort to find Eclipse Echoes, also on non-eclipsing binaries; (Doyle)






long-monitoring 2-3yrs: 267k stars 80ppm/√h

First order, multiply Kepler detection rates by 1.66 -> 10 ‘Kepler CBP’

Step&stare 2-5 months: 106 stars

Reduced detection capability for longer-periodic (p>0.2yr) CBPs.

Assuming that ½ of known Kepler CBP detected in such data: -> 20 ‘Kepler CBP’

Estimates for short-periodic CBP and those found by Eclipse Echo: depending strongly on findings from Kepler.



Tasks of the cbp working group
Tasks of the CBP working group

  • Sample definition: definition of expected sample for circumbinary planet searches (e.g. sample size and characteristics). This needs to be performed in light of capabilities of the available detection methods. It consists in an initial estimate for the sample, which will be refined and updated alongside the evolution and eventual freezing of PLATO mission specs.

  • Detection methods:

    • Initially: revision of existing methods and algorithms. This includes: evaluation of their sensitivity, requirements onto PLATO data; need for auxiliary data or parameters (e.g. stellar masses); potential results ('discovery space').

    • Selection of one or two methods and their development towards implementation in PLATO data analysis protocol. Testing of these methods with simulated data and definition of their performance.

  • Feedback to PLATO science coordination about design aspects that may allow an optimization of the mission towards the WP objectives

  • Definition of auxiliary data that will be needed: revising their availability in literature or databases or defining the observations required from other instruments (ground or space). Pre-launch catalogue of EBs needed? Some Algorithms (e.g. CB-BLS) need stellar mass-ratio.


Thank you