Tentative detection of sodium and ionized calcium from the exoplanet 55 Cancri e Andrew Ridden-Harper I. A. G. Snellen, C. U. Keller, R. J. de Kok, E. Di Gloria, H. J. Hoeijmakers, M. Brogi, M. Fridlund, B. L. A. Vermeersen, W. van Westrenen, A. van den Berg Andrew Ridden-Harper, Groningen PEPSci meeting 15/1/2016 What do we already know? Mass Radius 8 Earth masses 2 Earth radii Density: 4 g cm-3 Two ideas: • Normal oxygen-rich silicate & iron composition → Hydrogen or water atmosphere Gillon et al. 2012 • Unusual carbon-rich composition → no atmosphere (host star is carbon rich) Madhusudhan et al. 2012 Very high temperature Orbits very close to host star experience intense radiation possible tidal heating Mercury 55 Cancri e Orbital distance (AU) 0.387 0.016 Equilibrium temp (K) ~435 ~1900 Observed temperatures between 1300 and 2800 K volcanic activity? circumstellar/circumplanetary disk? (Demory et al. 2015) Exosphere of Mercury from sputtering Impact of radiation & energetic particles from Sun Ejects atoms from surface Creates exosphere of surface material Na exosphere of Mercury observed by MESSENGER (NASA) Extend to exoplanets Close-in rocky exoplanets hotter than Mercury More extreme exosphere that might be detected? Simulated Na exosphere of CoRoT-7b Mura et al. 2011 Guenther et al. 2011 observed CoRoT-7b Non-detection and upper limits 55 Cnc 200 times brighter than CoRoT-7 Higher S/N so better chance of detection 55 Cancri e data 5 time series spectroscopic transit data sets: 1xUVES/VLT (8m, clouds) (only for Na) 2xHARPS/ESO 3.6m (3.6m) 2xHARPS-N/TNG (3.68) (for Na and Ca+) Resolution R ~ 100000 Source: http://www.aip.de/groups/opti/MUSE/ time Planet’s changing radial velocity wavelength Image credit: Remco de Kok Process to remove stellar and telluric lines Divide by median spectrum time Remove wavelength structure with PCA Very strong injected signal of 5% (demonstration purposes only) (Indicated regions are approximate) Very strong injected signal of 5% (demonstration purposes only) (Indicated regions are approximate) Shift to planet frame (5% injected signal) Shift to planet frame (5% injected signal) Sum Shift to planet frame (5% injected signal) Sum S/N = 16 ~3.1𝜎𝜎 of Na from average ~3.1𝜎𝜎 of Na from average Average Na ~4.8𝜎𝜎 Ca+ in only HARPS A ~4.8𝜎𝜎 Ca+ in only HARPS A HARPS A zoom-in ~4.8𝜎𝜎 Ca+ in only HARPS A HARPS A zoom-in Blue shift Possible tail interpretations Mura et al. 2011 Bourrier et al. 2015 Conclusions Na: 3.1𝜎𝜎 in weighted average Ca+: 4.8𝜎𝜎 in only one dataset If detection of Ca+ is real, 55 Cancri e must be highly variable If confirmed, would be evidence against a hydrogen or water atmosphere Follow-up observations with UVES/VLT on the way Andrew Ridden-Harper, Groningen PEPSci meeting 15/1/2016 Estimate of physical scale of absorbing cloud Radius of optically-thick spherical cloud that would absorb the same as what is absorbed by 55 Cancri e Na Determine absorption by injecting artificial signal early in analysis Corresponds to an optically-thick Na cloud filling Roche lobe Ca+ Corresponds to optically-thick cloud of radius 5× Roche lobe radius (possibly extended tail) Faint trace of Ca+ signal across spectra 55 Cancri e UVES data analysis time Stack the spectra in a matrix wavelength 55 Cancri e UVES data analysis time Stack the spectra in a matrix wavelength Follow up observations Two more transits with UVES/VLT Time was allocated, now working on phase 2 details Possibility of two more transits in next VLT semester Monitor for possibility of variability
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