From astrobites: “Blurred Lines: degeneracies in modeling exoplanet atmospheres”

Astrobites bloc

From astrobites

Title: The theory of transmission spectra revisited: a semi-analytical method for interpreting WFC3 data and an unresolved challenge
Authors: Kevin Heng, Daniel Kitzmann
First Author’s Institution: University of Bern, Center for Space and Habitability

Status: Accepted to MNRAS, open access

Transmission spectroscopy is the most commonly used method to characterize the atmospheres of transiting exoplanets that have been discovered to date. The method is seemingly straightforward: photons from the host star passing through the limb of its transiting exoplanet are absorbed or transmitted by the planetary atmosphere to a varying extent in different wavelengths, which should appear as a variation in observed radius of the exoplanet with respect to wavelength. This variation in transit radius with wavelength, known as transmission spectrum, can then be interpreted by adopting either a forward or inverse modeling approach. This means that you can either start with a set of assumptions for the atmospheric properties (like chemical abundances, cloud properties etc.) and construct a physical model that can be fit to the data, or try solving the inverse problem (also known as retrieval) and infer the atmospheric properties from the measured transmission spectra itself.

However, there is a good deal of subtlety behind both approaches of constructing theoretical models for transiting exoplanet atmospheres. Today’s paper traces the assumptions and caveats involved in constructing models for observations taken by the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope.

NASA/ESA Hubble Telescope

NASA/ESA Hubble WFC3

In addition to deriving a validated semi-analytical approach from first principles for calculating the transmission spectra in the context of WFC3 observations, authors of today’s paper uncover a crucial and unresolved degeneracy involved in fitting a model to the transmission spectra.

See the full article here .


five-ways-keep-your-child-safe-school-shootings

Please help promote STEM in your local schools.
stem
Stem Education Coalition

What do we do?

Astrobites is a daily astrophysical literature journal written by graduate students in astronomy. Our goal is to present one interesting paper per day in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.
Why read Astrobites?

Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.
Our goal is to solve this problem, one paper at a time. In 5 minutes a day reading Astrobites, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in a new area of astronomy.