Download Planetary compositions from disrupting exoplanets

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
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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
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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
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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:
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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