Broadband Eclipse Spectra of Exoplanets are Featureless?

View previous topic View next topic Go down

Broadband Eclipse Spectra of Exoplanets are Featureless?

Post by Sirius_Alpha on 28th February 2014, 5:45 am

Broadband Eclipse Spectra of Exoplanets are Featureless

Spectral retrieval methods leverage features in emission spectra to constrain the atmospheric composition and structure of transiting exoplanets. Most of the observed emission spectra consist of broadband photometric observations at a small number of wavelengths. We compare the Bayesian Information Criterion (BIC) of blackbody fits and spectral retrieval fits for all planets with eclipse measurements in multiple thermal wavebands, typically hot Jupiters with 2-4 observations. If the published error bars are taken at face value, then eight planets are significantly better fit by a spectral model than by a blackbody. In this under-constrained regime, however, photometric uncertainties directly impact one's ability to constrain atmospheric properties. By considering the handful of planets for which eclipse measurements have been repeated and/or reanalyzed, we obtain an empirical estimate of systematic uncertainties for broadband eclipse depths obtained with the Spitzer Space Telescope: sigma_sys = 5E-4. When this systematic uncertainty is added in quadrature to published uncertainties, the Bayesian evidence for spectral features disappears: blackbodies have better BIC for all planets. Stratospheric inversions, high C/O ratios, disequilibrium chemistry, and He-dominated atmospheres have been inferred from spectral features in broadband eclipse photometry, and are therefore suspect. We conclude that statements about atmospheric composition and structure based solely on photometry are premature.

A rather short paper. I'm afraid I don't know a lot about the content but maybe someone would offer some insight?

Caps Lock: Cruise control for 'Cool'!

Number of posts : 3443
Location : Earth
Registration date : 2008-04-06

View user profile

Back to top Go down

View previous topic View next topic Back to top

Permissions in this forum:
You cannot reply to topics in this forum