Andrew Carter, Carole Haswell, The Open University

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HST observations of WASP transiting exoplanets

• Andrew Carter, Carole Haswell, The Open University

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HST observations of WASP transiting exoplanets
Andrew Carter, Carole Haswell, The Open
University Will Clarkson STScI, Leslie Hebb, St
Andrews, Frederic Pont, Exeter The WASP
consortium
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Talk Outline

• WASP project
• Overview of WASP HST follow-up programme
• - pM and pL class planets with or without T
  inversion
• - hydrodynamic blow-off
• NICMOS Observations of WASP-2
• Transmission Spectrum Extraction
• Preliminary Results

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SuperWASP Wide Angle Search for Planets

• S. Aigrain (Cambridge -gt Exeter)
• D. Anderson (Keele)
• S. Bentley (Keele)
• A. Carter (Open University)
• D.J. Christian (Belfast)
• W.I. Clarkson (Open University -gt STScI)
• A. Collier Cameron (St Andrews)
• B. Enoch (Open University-gt St Andrews)
• N.Gibson (Belfast)
• C.A. Haswell (Open University)
• L. Hebb (St Andrews)
• C. Hellier (Keele)
• K. Horne (St Andrews)
• J. Irwin (Cambridge -gt CfA Harvard)
• Y. Joshi (Belfast)
• S.R. Kane (St Andrews -gt Caltech)
• F.P. Keenan (Belfast)
• T.A. Lister (St Andrews/Keele -gt LCOGT)
• P. Maxted (Keele)

With F. Bouchy (IAP) G. Hébrard (IAP) F. Pont
(Geneva-gtExeter) B. Loeillet (Marseille) M.
Gillon (Geneva) M. Mayor (Geneva) C. Moutou
(Marseille) F. Pepe (Geneva) D. Queloz
(Geneva) A.M.H.J. Triaud (St Andrews -gt
Geneva) S. Udry (Geneva)
Out of date!
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The WASP transit surveys

• Pollacco et al 2006, PASP 118, 1407
• Lenses
• Canon 200mm f/1.8
• Aperture 11.1 cm
• CCD Detector
• 2048 x 2048 thinned e2v (Andor, Belfast)
• 13.5x13.5 micron pixels
• Field of View
• 7.8 x 7.8 degrees
• 13.7 arcsec/pixel
• Mount
• OMI/Torus robotic mount
• Operating Temperature
• 50 ºC
• 3-stage Peltier Cooling

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Correlated noise in light curves

• differential photometry easy in principle
• in practice there are complexities
• e.g. focus depends on position on detector
  temperature 2 pix lt FWHM lt 3.5 pix i.e. 28
  arcsec 50 arcsec

Parley, 2008 (OU PhD thesis)
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WASP family portrait album
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WASP family references
WASP-1, -2 WASP-3 WASP-4 WASP-5 WASP-6 WASP-7 WASP
-8 WASP-9 WASP-10 WASP-11 WASP-12 WASP-13 WASP-14
WASP-15
Collier Cameron et al 2007, MNRAS Pollacco et al
2007, MNRAS Wilson et al 2008, ApJ Anderson et al
2008, MNRAS WASP-S planet Hellier et al 2008,
submitted Queloz et al 2008 in prep WASP-S
planet Christian et al 2008, in prep West et al
2008, in prep Hebb et al 2008, in prep Skillen et
al 2008, in prep Joshi et al 2008, in prep WASP-S
planet
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HST spectrophotometry

• WASP-1 NICMOS data recently taken
• WASP-2 NICMOS data in hand, reduction pipeline
  developed, analysis in progress
• WASP-3 have 3 visits of NICMOS data, awaiting
  4th. Hope to detect hot stratosphere.
• WASP-12 (hottest known to date) cycle 17 COS
  observations pending all PI
  Haswell

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2 Classes of Hot Jupiters
pM Class hot enough for gaseous TiO and VO pL
Class TiO and VO condensed
Fortney et al 2007
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pM and pL class planets
Prediction 6 enhancement in transit depth
distinct radius(?) curves Test with NICMOS
(now), STIS, WFC3? and/or ACS? Possible advances
i) cold-trap not well-understood
ii) atmospheres not iterated to
radiative- convective equilibrium
- may affect emergent spectrum - how
important is disequilibrium chemistry?

Fortney et al 2007
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Irradiating flux-radius relation

• Includes the new WASP planets
• Circle size indicates planet mass
• R increases with flux, but MUCH scatter
• Many other variables
• Planet mass not a dominant variable
• WASP-12 highlighted
• HD 147506b not shown (M 8 Mjup, R0.98 Rjup)

Hebb et al 2008 Boston poster
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Hubbles UV capability to be restored!

• 10x previous UV sensitivity COS
• Detailed transmission spectroscopy of atmospheres
  possible
• Probe composition, vertical structure, mass loss
• Probe atmospheric dynamics?
• HD 209458b surrounded by HI cloud larger than
  Roche lobe
• Hydrodynamic blow-off?

HD 209458b Ly a silhouette
Vidal-Madjar et al (2003) Nature 422, 123
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Test hydrodynamic blow-off hypothesis

• HD 209458b surrounded by HI cloud larger than
  Roche lobe
• Hydrodynamic blow-off
• Interpretation above questioned
• Stellar Ly a variable geocoronal contamination
• Depth depends on wavelength bins used
• 8.9 2.1 depth inside Roche lobe

Vidal-Madjar et al (2003) Nature 422, 123
Ben-Jaffel (2007) ApJ, 671, L61
HD 209458b Ly a silhouette
?
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Test hydrodynamic blow-off hypothesis

• WASP-12b ideal target
• Hottest planet
• Most bloated planet
• Shortest period planet
• closest to host star
• But WASP-12 at V12, Teff6500 too faint to do
  at Ly a
• Hydrodynamic blow-off
• OI and CII entrained in HD 209458b blow off
• Observe transit in Mg II near-UV triplet at 2800Å
• Mg is abundant element, should be entrained in
  blow-off
• transition is from the ground state
• Mg II has lower ionisation potential than C II
• Gaseous Mg II should be evaporated from cloud
  deck

Hebb et al 2008 in prep
Vidal-Madjar et al 2004
HST GO-11651 PI Haswell
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Test hydrodynamic blow-off hypothesis

• Gaseous Mg II should be evaporated from cloud
  deck
• Models by CoI Helling

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Observations

• WASP-2
• HST / NICMOS / NIC3 / G141
• defocus to increase duty cycle
• resolution 0.1µ
• dispersion 0.01 µm / pixel
• time-resolution 50 Sec
• 2 visits
• 4 Orbits ingress egress visit 3
• 3 Orbits transit floor visit 4

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Data reduction Required

• Extract broad-band light curves
• robust method collect all 1st order light
• ignore 2nd order light (lt 20 of photons)
• Remove Systematic Effects
• decorrelation / regression against HST state
  parameters
• Extract Wavelength-resolved light curves
• collapse PSF in spatial direction LSF
• Fit sum of monochromatic LSFs to spectrum

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Exoplanet atmospheric chemistry

• Transmission spectroscopy depth(?)
• Line opacity and silhouette radius
• characterise atmospheric physics and chemistry

From Brown (2001) ApJ 553 1006
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Transmission Spectroscopy

• Previous methods have binned Data
• Few Points
• Low Wavelength Resolution
• NICMOS G141 resolution degraded by Defocusing
• maximise resolution by LSF reconstruction
• Work in progress!

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WASP-2 spectrum, G141 data
Counts spectrum is dominated by the inverse
sensitivity function.
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WASP-2 spectrum, G141 data
WASP-2 K3 V Spectral slope and wiggles
imperfect ? calibration
Rayner et al 2003, PASP, 115, 362
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Transmission Spectroscopy

• Line Spread Function (LSF) Profiling

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Transmission Spectroscopy

• LSF Profiling

collapse PSF Line Spread Function (LSF) 10
pixel wide
?2 fit model spectrum to observed spectrum
point spread function (PSF) from Direct Images
contribution of each LSF gives monochromatic
flux in Image
normalise LSF
multiply Siby normalised LSF, create model
spectrum
repeat for each image nwave monochromatic ligh
t curves
nwave scale factors, Si
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Transmission Spectroscopy

• Profiling Algorithm

use final Si, as estimate for next image
estimate initial scale factors, Si
NO Model has converged
multiply Siby normalised LSF, create model
spectrum
?2 of fit improved?
Smooth the model
calculate new Si From residuals
YES
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Transmission Spectroscopy
Work in progress fit not yet sharp enough
LSF
?? increasing
Column number
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Transmission Spectroscopy

• Decorrelating Wavelength Dependent Curves
• Apply global Decorrelation Parameters
• Include Local Decorrelation Parameters
• Background, Y Position Width
• Calculated as an average of columns, weighted
  according to the LSF

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Transmission Spectroscopy
Decorrelation problematic for visit 4,
insufficient OOT
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LSF fitting status

• Profiling Algorithm seems to give sensible
  results
• - independent of direction in time
• - independent of direction in wavelength
• Smoothing required to prevent oscillations
• - prevents good fit to stellar spectrum
• - need to fit, reduce smoothing, iterate
  further
• Preliminary results encouraging
• - depth plot affected by poorly fit features
• - need to refine wavelength calibration

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Transmission Spectroscopy

• Preliminary results
• not to be believed yet!

• Many wiggles in depth spectrum correspond to
  features in stellar spectrum

We still have more work to do, but approach looks
promising?