Circumbinary Planet Detection with PLATO

1. 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 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 PLATO 2.0 WS

2. 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 PLATO 2.0 WS

3. 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 PLATO 2.0 WS

4. Circumbinary planet detection • Several photometric methods: • Eclipse timing variations (ETV) • Transits • ‘Eclipse Echos’ • No RV discovery, but ongoing TATOOINE Search (Konacki+ 2009) PLATO 2.0 WS

5. 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 PLATO 2.0 WS

6. 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 PLATO 2.0 WS

7. eclipse in reflected light from planet Eclipse Echos Detection of binary eclipses in planet’s reflected light Deeg & Doyle 2011 PLATO 2.0 WS

8. 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 PLATO 2.0 WS

9. 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) Planet-period Planet-mass Deeg+ 2000 Max. a for Transit-discovery given by inclination of binary, assuming coplanar planet

10. 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) K47 K35K64 K16 K34 PLATO: 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. P=41d PLATO 2.0 WS

11. 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. PLATO 2.0 WS

12. Thank you ¡Gracias! PLATO 2.0 WS