WASP-12

System

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

WASP-12b Discovered 2008 Extremely hot Jupiter Orbital radius of 0.023 AU (essentially circular) Period of 1.09 days 1.7 RJ, 1.4 MJ Eccentricity 0 +- .01 ~3 stellar radii https://astrobites.org/2015/04/29/and-the-saga-continues-the-story-of-exoplanet-wasp-12b/

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) http://www.nasa.gov/mission_pages/spitzer/multimedia/pia13690.html

Observations

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

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

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

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

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

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

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)

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

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

References https://arxiv.org/pdf/1005.3656.pdf https://arxiv.org/pdf/1301.1860.pdf https://arxiv.org/pdf/1303.3375v1.pdf https://arxiv.org/pdf/1512.01555v1.pdf