1. WASP-12

2. System

3. WASP-12 Magnitude 11.7 yellow dwarf 800 ly, in Auriga
Sunlike – 1.35 M☉ , 1.6 R☉
2 companions, ~0.5 M☉ each
800 ly, in Auriga
RA 06:30:33.0, Dec +29:40:20
CW from bottom, Orion, Gemini, Auriga, Taurus
wikisky.org

4. WASP-12b Discovered 2008 Extremely hot Jupiter
Orbital radius of AU (essentially circular)
Period of 1.09 days
1.7 RJ, 1.4 MJ
Eccentricity
~3 stellar radii

5. WASP-12b Infrared spectroscopy predicts carbon-rich planet
Yellow – data
Blue – model curve averaged to cover wavelengths of data (observational spectra in gray at bottom)

6. Observations

7. Presence of Exosphere Multiple observations performed with HST
2010 – evidence for extended cloud of gas ≥ Roche lobe
Absorption from metals in near UV
Cosmic Origins spectrograph

8. Possible Mechanisms Tidal disruption
Eccentricity too low for WASP-12b
Hydrodynamic blow-off from irradiation
Charge exchange creating cloud of hot H
Entrainment of material from stellar corona

9. Detailed Examination
In addition to HST, ground observations with PIRATE, Faulkes North, and James Gregory
All NUV
HST observations optimized for Mg II (doublet near 2800 Å) and Fe II (2586 Å)
Coverage overlaps for half total coverage
Occulting size in NUV significantly larger than optical size
NUV allows gas detection at any velocity (FUV [Lyman alpha] undetectable outside velocity width of line emission)
Spectral resolution of ~20000

10. Absorption Lines
Synthetic stellar spectrum = blue line, not used in analysis
Shown points are 3 sigma or greater – either from propagated errors, or from RMS scatter within spectrum (more likely to detect absorption where stellar signal is low)
~200 significant lines/visit

11. Absorption Lines Fe II (top) and Mg II (bottom) clear in data
Mg II cores “conspicuously absent”

12. Required Column Density
Absence of Mg II lines extremely anomalous
Column density from interstellar medium ~2x1016 /cm2
Order of magnitude less than would produce absorption profile similar to observation

13. Estimates of Column Density
Estimate maximum column density using cylinder with height of stellar diameter and orbital radius
Get 4x1021 /cm2
I get different result using their numbers:
Equality when all mass is captured (none escaping or absorbed by star)

14. Estimates of Column Density
Better estimate would be using a torus of major radius equal to orbital radius and minor radius equal to stellar radius

15. Magnetic Simulations
Interaction of stellar Parker wind with planetary gravity and magnetic field
No planetary outflows
Stellar parker wind set at boundary as inflow condition, then allowed to evolve to steady state

16. References https://arxiv.org/pdf/1005.3656.pdf