Transits What questions to ask? What are the observables? Constraints on precision? Model interpretation? Ground-based? Space-borne? All-sky vs. pointed Follow-up observations (confirmation) issues What is already being done and what needs to be done? What are the risks?

10 Big Questions (1)Where are the earthlike planets, and what is their frequency? (2) What is the preferred method of gas giant planet formation? (3) Under which conditions does migration occur and stop? (4) What is the origin of the large planetary eccentricities? (5) Are multiple-planet orbits coplanar? (6) How many families of planetary systems can be identified from a dynamical viewpoint? (7) What are the atmospheres, inner structure, and evolutionary properties of gas giant planets, neptunes, and telluric planets? (8) Do stars with circumstellar dust disks actually shelter planets? (9) What are the actual mass and orbital element distributions of planetary systems? (10) How do planet properties and frequencies depend on the characteristics of the parent stars (spectral type, age, metallicity, and binarity/multiplicity)? ELSA School - Leiden, 11/22/2007

Transit Photometry * Observable: decrease of stellar brightness, when planet moves across the stellar disk * Condition of observability: planetary orbit must be (almost) perpendicular to the plane of the sky * The method allows a determination of parameters that are not accessible with Doppler spectroscopy, e.g. ratio of radii, orbital inclination, limb darkening of the star Probability of Eclipses: It is easier to detect an eclipse by a planet on a tight orbit ELSA School - Leiden, 11/22/2007 Must combine with RV in order to derive mass and radius of the planet

Transit Depth and Duration ELSA School - Leiden, 11/22/2007 Warning! Prone to a variety of astrophysical false alarms 52 Transiting systems are known to-date

Mimicking Planetary Transits Eclipsing binaries: - grazing - low-mass companion - multiple systems and blends Typically, 95%-99% of detections…

Ljubljana University, 4/15/2008 The M p -R p Relation Roughly OK Very large core? Coreless?? Default models have trouble! Transiting planets come in many flavors What are their actual interiors? How did they form?

Ljubljana University, 4/15/2008 The M c – [Fe/H] Connection ? Burrows et al. (ApJ, 2007): “The core mass of transiting planets scales linearly (or more) with [Fe/H]” Guillot et al. (A&A, 2006): “The heavy element content of transiting extrasolar planets should be a steep function of stellar metallicity”? Do inferred exoplanets core masses depend on metallicity?

How well do we know the Hosts? Main-stream approach: main-sequence stars astrophysics is a solved problem, for practical purposes For transiting systems, the star is most of the time the limit (mass, radius, limb- darkening)!

Ljubljana University, 4/15/2008 Improving R *, M *, R p, M p Sozzetti et al. (ApJ, 2007) 1<t<9 Gyr [Fe/H] = The uncertainty on R * is several times smaller if a/R * is used instead of log(g) By combining: 1)stellar properties, 2)spectroscopic mass function, 3)light-curve parameters One obtains improved values for: 1)planet radius, 2)planet mass, 3)planet gravity TrES-2

Transiting Systems Follow-up (1) Visible Transits: - radius, density, composition, moons or other planets, spin-orbit alignment ELSA School - Leiden, 11/22/2007 Winn et al Holman et al. 2005

Transiting Systems Follow-up (2) Infrared Transits Infrared Transits –Temperature, reflectivity and composition, rotation, winds ELSA School - Leiden, 11/22/2007 Knutson et al Burrows 2007 Charbonneau et al. 2005

Photometric Precision mag is achieved from the ground (high-cadence, meter-sized telescopes) For Earth-sized companions / solar-type stars, need better than mag The latter cannot be achieved from the ground (and again, the star is the likely limit!)

In addition… Transit timing variations allow to infer the presence of additional components If more than one transit, derive densities directly from photometry alone Must achieve very high timing precision (1-10 sec typically). Difficult from the ground

At present… CoRoT & Kepler, pointed, and possibly TESS, all-sky can provide much of the observational material of quality needed to address many issues There is a time niche from the ground for M dwarfs transit searches.

Plato

Confirmation observations Very time-consuming For CoRoT & Kepler (and all the more for Plato) targets may not even be feasible below a certain radius size. Followup Decision Tree

Astrometry What questions to ask? What observables? What constraints on precision? Model interpretation? Filled-aperture vs. diluted From the ground? From space? All-sky vs pointed. What is already being done and what needs to be done? What are the risks?

August 27, 2008 Exoplanets in Multi-Body Systems Torun, Poland What about Astrometry? Astrometry measures stellar positions and uses them to determine a binary orbit projected onto the plane of the sky Astrometry measures stellar positions and uses them to determine a binary orbit projected onto the plane of the sky Astrometry measures all 7 parameters of the orbit, in multiple systems it derives the Astrometry measures all 7 parameters of the orbit, in multiple systems it derives the relative inclination angles between pairs of orbits, regardless of the actual geometry. Mass is derived given a guess for the primary’s. In analysis, one has to take the proper motion and the stellar parallax into account In analysis, one has to take the proper motion and the stellar parallax into account The measured amplitude of the orbital motion (in milli-arcsec) is: The measured amplitude of the orbital motion (in milli-arcsec) is:

August 27, 2008 Exoplanets in Multi-Body Systems Torun, Poland Success: HST/FGS Follow-up A mass for GJ 876cA mass for GJ 876c A mass for ε Eri bA mass for ε Eri b A mass for the Neptune-sized ρ 1 Cnc d (if coplanar)A mass for the Neptune-sized ρ 1 Cnc d (if coplanar) Not a planet but an M dwarf: HD bNot a planet but an M dwarf: HD b Benedict et al. 2002, 2006; McArthur et al. 2004; Bean et al. 2007

August 27, 2008 Exoplanets in Multi-Body Systems Torun, Poland μas Astrometry is needed But it’s difficult! From the ground: photon noise, instrumental noise, atmospheric noise (turbulence+DCR) In space: more random/systematic noise sources: attitude errors (solar wind, micrometeorites, particle radiation, radiation pressure, thermal drifts and spacecraft jitter), CTI, and so on… Secular changes in the target motion (perspective accelerations), relativistic corrections due to a) the observer’s motion (aberration) and b) the gravitational fields in the observer’s vicinity (light deflection)Astrophysical ‘effects’: Secular changes in the target motion (perspective accelerations), relativistic corrections due to a) the observer’s motion (aberration) and b) the gravitational fields in the observer’s vicinity (light deflection) strometric ‘jitter’ intrinsic to the target: spots, faculae, flares, etc., astrometric ‘jitter’ due to environment: disks, stellar companionsAstrophysical ‘noise’: astrometric ‘jitter’ intrinsic to the target: spots, faculae, flares, etc., astrometric ‘jitter’ due to environment: disks, stellar companions

August 27, 2008 Exoplanets in Multi-Body Systems Torun, Poland VLTI/PRIMA The recorded distance between white fringes of the reference and the object is given by the sum of four terms: (ΔS. B) the Angular separation (< 1 arcmin) times Baseline; + (Ф ) the Phase of Visibility of Object observed for many baselines; + (ΔA) the Optical Path Difference caused by Turbulence (supposed averaged at zero in case of long time integration); + (ΔC) the Optical Path Difference measured by Laser Metrology inside the VLTI. n.b. For astrometry both Objects are supposed to have the Phase of their complex visibility = zero (point source object) Expected to reach the atmospheric limiting precision of ~10-20 μas

August 27, 2008 Exoplanets in Multi-Body Systems Torun, Poland ESPRI Consortium AT ? FSU A/B Delay lines Instrument getting close to commissioning The Consortium will carry out a two-fold program (astrometry of known systems, The Consortium will carry out a two-fold program (astrometry of known systems, planet search around stars of various spectral types and ages) planet search around stars of various spectral types and ages)

August 27, 2008 Exoplanets in Multi-Body Systems Torun, Poland Adaptive Optics/Coronagraphy See next talk and poster by Helminiak & Konacki AO + symmetrization of the reference frame to remove low-f components of the image motion spectrum and improve image centroid. Lazorenko 2004,2006 Predicting the star location with respect to the occulting spot from image centroid, instrument feedback, or PSF symmetry still results in mas precision at best Digby et al V=15, t=10 min

August 27, 2008 Exoplanets in Multi-Body Systems Torun, Poland Gaia Discovery Space (1) Gaia can measure accurately > 50% of the present-day exoplanet sample 1)Massive planets (>2-3 M J ) at M J ) at 2<a<4 AU are detectable out to ~200 pc around solar analogs 2) Saturn-sized planets with 1<a<4 AU are measurable around nearby (<25 pc) M dwarfs Casertano, Lattanzi, Sozzetti et al. 2008

August 27, 2008 Exoplanets in Multi-Body Systems Torun, Poland Gaia Discovery Space (2) How Many Planets will Gaia find? How Many Multiple-Planet Systems will Gaia find? Star counts (V<13), F p (M p,P), Gaia completeness limit Star counts (V<13), F p,mult, Gaia detection limit Casertano, Lattanzi, Sozzetti et al. 2008

August 27, 2008 Exoplanets in Multi-Body Systems Torun, Poland The Gaia Legacy (1) How do Planet Properties and Frequencies Depend Upon the Characteristics of the Parent Stars (also, What is the Preferred Mechanism of Gas Giant Planet Formation?)? Gaia will test the fine structure of giant planet parameters distributions and frequencies, and investigate their possible changes as a function of stellar mass, metallicity, and age with unprecedented resolution 10 4 stars per 0.1 M Sun bin! Johnson 2007 Casertano et al ? Sozzetti et al. 2008

August 27, 2008 Exoplanets in Multi-Body Systems Torun, Poland The Gaia Legacy (2) How Do Dynamical Interactions Affect the Architecture of Planetary Systems? E.g., coplanarity tests will allow to determine the relative importance of many proposed mechanisms for eccentricity excitation in a statistical sense, not just on a star-by-star basis. Thommes & Lissauer 2003 a)Interactions between a planet and the gaseous/planetesimal disk? gaseous/planetesimal disk? b)Planet-planet resonant interactions? c)Close encounters between planets? d) Secular interactions with a companion star?

August 27, 2008 Exoplanets in Multi-Body Systems Torun, Poland A word of Caution… If the single-measurement precision degrades significantly, exoplanets could disappear from the Gaia science case Casertano, Lattanzi, Sozzetti et al. 2008

August 27, 2008 Exoplanets in Multi-Body Systems Torun, Poland SIM DBT Campaign (1) Planetary systems can be reliably detected and characterized, with a relatively small number of false detections

August 27, 2008 Exoplanets in Multi-Body Systems Torun, Poland SIM DBT Campaign (2) All detectable planets (above a SNR~6 threshold) were in fact detected All detectable planets (above a SNR~6 threshold) were in fact detected Terrestrial planets orbits can be characterized even in presence of gas giants Terrestrial planets orbits can be characterized even in presence of gas giants

August 27, 2008 Exoplanets in Multi-Body Systems Torun, Poland Which directions? Ground-based astrometry appears to have limited potential for detection, but can contribute significantly to better the knowledge of existing systems. In Space, synergy Gaia/SIM (and/or TESS/Plato)? If SIM won’t be there, what else?

August 27, 2008 Exoplanets in Multi-Body Systems Torun, Poland Transits WG Cristina Afonso Roi Alonso David Blank Claude Catala' Hans Deeg Coel Hellier David W. Latham Dante Minniti Frederic Pont to be Heike Rauer

August 27, 2008 Exoplanets in Multi-Body Systems Torun, Poland Astrometry WG Fabien Malbet, Petro Lazorenko, Sabine Reffert, Alessandro Sozzetti, Nick Elias, Ralf Launhardt, Matthew Muterspaugh, Gerard van Belle, Andreas Quirrenbach, Francoise Delplanck,