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Planetary compositions from disrupting exoplanets Carole Haswell, The Open University Jakub Bochinski, Dan Staab, John Barnes, Luca Fossati, Guillem Angelada-Escude, Small close-in planets: important targets for PLATO Talk Outline: • Background – Planet compositions • KIC 1255: – disintegrating – composition from extended gas & dust cloud – Other similar objects • Analogues around nearby stars – optical signature of shrouded planetary systems: R’HK – hot Jupiters – Low R’HK work – Identify RV targets • the big picture: where should we be by PLATO launch? Planet Compositions Bulk density depends on structure and composition Radius measurement -> bulk composition far from unique determination of composition! Zeng & Sasselov, 2013 PASP ; 2014, ApJ Planet Compositions Spectral signatures in reflected/emitted light by phase modulation or secondary eclipse Spectral features molecules present Limited to atmospheric rather than bulk composition Collier Cameron et al Nature 1999, Barnes et al MNRAS 2007a, 2007b, 2008, 2010. Rodler, Kurster & Barnes MNRAS, 2013, Birkby et al MNRAS 2013, Brogi et al A&A 2014, Planet Compositions Transmission spectroscopy spectral signatures in transmitted light Spectral features molecules present Limited to atmospheric (at limb) rather than bulk composition Crucially dependent on scale-height of atmosphere Brown (2001) ApJ 553: 1006; Vidal-Madjar et al (2003) Nature 422, 123 Mass-losing close-in planets e.g. KIC 1255b, WASP-12b have HUGE scale-heights Fossati, Haswell et al 2010, Haswell, Fossati et al 2012, Rappaport et al 2012, ApJ, 752, 1 Carole Haswell The Open UniversityPLATO 2.0 Brogi et al 2012 A&A 545, L5 mtg July 2013 KIC 1255b: disintegrating planet feeding transiting dust cloud • • • • 0.1 Earth mass transiting planet, 15.7 hour orbit around a KV star T = 2100 K, direct sublimation and/or explosive volcanism Large cloud of metal-rich vapour and entrained dust lost from planet Limit cycle: dust forms, t raised, surface cools, sublimation slows, less dust, t decreases, surface heats, sublimation increases, dust forms, … Carole Haswell The Open UniversityPLATO 2.0 mtg July 2013 Brogi et al 2012 A&A 545, L5 Rappaport et al 2012, ApJ, 752, 1 A disintegrating close-in rocky planet KIC 1255 WHT/ULTRACAM observations July 2013 • deep & shallow transits in u’, g’, z’ • Shallow transits in u’, g’, i’ • Characterised with a simple transit to minimise model parameters – limb-darkening (Claret 2004) – Assume occulter presents circular cross-section – vary phase & radius • Wavelength-dependent depth • Night 1: transit deep & clearly detected in u’, g’, z’ • Scaled Kepler profile (shown) matches z’ and g’ light curves Bochinski, Haswell, Marsh, Dhillon & Littlefair 2014, ApJLett, submitted Carole Haswell The Open UniversityPLATO 2.0 mtg July 2013 A disintegrating close-in rocky planet KIC 1255 WHT/ULTRACAM observations July 2013 • deep & shallow transits in u’, g’, z’ • Shallow transits in u’, g’, i’ • Characterised with a simple transit to minimise model parameters – limb-darkening (Claret 2004) – Assume occulter presents circular cross-section – vary phase & radius • Wavelength-dependent depth • Night 1: transit deep & clearly detected in u’, g’, z’ • Scaled Kepler profile (shown) matches z’ and g’ light curves Bochinski, Haswell, Marsh, Dhillon & Littlefair 2014, ApJLett, submitted Carole Haswell The Open UniversityPLATO 2.0 mtg July 2013 Disintegrating planet KIC 1255b • HUGE scale-height • direct sampling of bulk composition Bochinski 2015 PhD thesis; work in progress A disintegrating close-in rocky planet KIC 1255 Night 1 transit depths compared to interstellar extinction • Used Cardelli, Clayton & Mathis (1989) extinction “law” • Depths are consistent with ISM reddening • 3 < RV < 7 • RV = 3.1 typically in the diffuse ISM • Broadly, mean grain size increases with RV Bochinski, Haswell, Marsh, Dhillon & Littlefair 2014, ApJLett, submitted Composition of KIC 1255b • Mie scattering efficiency: function of composition and wavelength • Multiwavelength observations of transits of varying depth -> trace one of these curves • We have only 1 night of reliable depths so far… but ULTRACAM can tell us the composition of this dust cloud! Haswell et al observing proposal under review… Carole Haswell The Open UniversityPLATO 2.0 mtg July 2013 Croll et al 2014, arXiv:1403.1879 ApJ, Catastrophic Evaporation of Rocky Exoplanets • • • • • • • T > 2000K : rock vaporizes, thermal wind driven. Radiative-hydrodynamic modelling with dust-gas energy exchange Small planets evaporate completely Mass loss rate depends strongly on planet mass KIC 1255 ~0.1 Earth mass, ~mass of moon KIC 1255 in final short-lived catastrophic phase, ~1% of planet life many progenitor low-mass short period rocky planets should exist. Perez-Becker & Chiang, 2013, arXiv:1302.2147 ApJ, Carole Haswell The Open UniversityPLATO 2.0 mtg July 2013 Catastrophic Evaporation of Rocky Exoplanets KIC 1255 in final short-lived catastrophic phase, ~1% of planet life • Not unique! – KOI-2700b—A Planet Candidate with Dusty Effluents on a 22 hr Orbit – many progenitor low-mass short period rocky planets should exist. Rappaport et al. 2014 ApJ 784 40 doi:10.1088/0004637X/784/1/40 Carole Haswell The Open UniversityPLATO 2.0 mtg July 2013 Kepler planets are distant transiting exoplanet candidates from Kepler ~10 times more distant than SuperWASP planets Microlensing planets in Galactic bulge Transit surveys like SuperWASP sensitive to more distant host stars RV discoveries restricted to nearby stars Need to find the nearby analogues of KIC 1255b Near-UV Mg II Line Profiles • WASP-12’s line profile is unique • main sequence stars all show chromospheric emission cores • Emission cores indicate T increase in tenuous outer atmosphere • Heating by magnetic turbulence etc • Emission cores must be absorbed • Mg II h & k lines v. strong • Diffuse gas reduces stellar flux to zero in line cores • Similar signal in the optical Ca II H&K line cores Haswell et al 2012 , ApJ, 760, 79 Image of sun during total eclipse Near-UV Mg II Line Profiles • WASP-12’s line profile is unique • main sequence stars all show chromospheric emission cores • Emission cores indicate T increase in tenuous outer atmosphere • Heating by magnetic turbulence etc • Emission cores must be absorbed • Mg II h & k lines v. strong • Diffuse gas reduces stellar flux to zero in line cores • Similar signal in the optical Ca II H&K line cores Haswell et al 2012 , ApJ, 760, 79 WASP-12 system shrouded in diffuse absorbing gas Disintegrating planets around bright stars: find using Ca II H&K line cores • • • • Examined > 6000 bright stars with measured log R’HK Examined IUE archive Identified ~100 prospects Winnowed the best dozen targets – Already signs of RV variability in some of these • Proposing to observe with OHP/SOPHIE & HARPS Haswell, Staab, Barnes, AngladaEscude, Fossati OPTICON award: 5 nights OHP/SOPHIE in 2015A BRIGHT hosts of masslosing, low-mass, short period rocky planets? Carole Haswell The Open UniversityPLATO 2.0 mtg July 2013 Disintegrating planets around bright stars with PLATO: • • • • KIC 1255b is detectable only by its dust cloud Planet to small to produce detectable transits PLATO can give exquisite precision to measure the sizes of small close-in bodies Our log R’HK targets will include some too small to detect without space-based photometry Haswell, Staab, Barnes, McCune, Anglada-Escude, Fossati BRIGHT hosts of masslosing, low-mass, short period rocky planets? Carole Haswell The Open UniversityPLATO 2.0 mtg July 2013 Disintegrating planets around bright stars with PLATO: • • • • KIC 1255b is detectable only by its dust cloud Planet to small to produce detectable transits PLATO can give exquisite precision to measure the sizes of small close-in bodies Our log R’HK targets will include some too small to detect without space-based photometry • These small planets may still be suitable for transmission spectroscopy via extended clouds of gas? radius –composition relation for small planets Haswell, Staab, Barnes, Bochinski, McCune, Anglada-Escude, Fossati Carole Haswell The Open UniversityPLATO 2.0 mtg July 2013 Planetary compositions from disrupting exoplanets Carole Haswell, The Open University