RECORD
VLT/FORS2 comparative transmission spectroscopy II: confirmation of a cloud-deck and Rayleigh scattering in WASP-31b, but no potassium?
Earth and Planetary Astrophysics · Submitted 7 Feb 2017
abstract compiled · 2026-09-23 · no language-model review
The authors' main claim However, our FORS2 observations appear to rule out the large potassium feature previously detected using STIS, yet it is recovered from the HST/STIS data, although with reduced amplitude and significance ($\approx$2.5$\sigma$).
The compiled record
The paper's own sentences, arranged. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.
Open the compiled record
The abstract, sentence by sentence
We present transmission spectroscopy of the hot-Jupiter WASP-31b using FORS2 on the VLT during two primary transits. The observations cover a wavelength range of $\approx$400-840nm. The light curves are corrupted by significant systematics, but these were to first order invariant with wavelength and could be removed using a common-mode correction derived from the white light curves. We reach a precision in the transit depth of $\approx$140 ppm in 15 nm bins, although the precision varies significantly over the wavelength range. Our FORS2 observations confirm the cloud-deck previously inferred using HST/STIS. We also re-analyse the HST/STIS data using a Gaussian process model, finding excellent agreement with earlier measurements. We reproduce the Rayleigh scattering signature at short wavelengths ($\lesssim$5300 $\AA$) and the cloud-deck at longer wavelengths. However, our FORS2 observations appear to rule out the large potassium feature previously detected using STIS, yet it is recovered from the HST/STIS data, although with reduced amplitude and significance ($\approx$2.5$\sigma$). The discrepancy between our results and the earlier STIS detection of potassium ($\approx$4.3$\sigma$) is either a result of telluric contamination of the ground-based observations, or an underestimate of the uncertainties for narrow-band features in HST/STIS when using linear basis models to account for the systematics. Our results further demonstrate the use of ground-based multi-object spectrographs for the study of exoplanet atmospheres, and highlight the need for caution in our interpretation of narrow-band features in low-resolution spectra of hot-Jupiters.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | We present transmission spectroscopy of the hot-Jupiter WASP-31b using FORS2 on the VLT during two primary transits. | contribution 0.69 | 0.97 | 0.03 | asserted 0.98 |
| s1 | The observations cover a wavelength range of $\approx$400-840nm. | method 0.99 | 0.88 | 0.01 | asserted 1.00 |
| s2 | The light curves are corrupted by significant systematics, but these were to first order invariant with wavelength and could be removed using a common-mode correction derived from the white light curves. | method 0.76 | 0.91 | 0.02 | asserted 0.79 |
| s3 | We reach a precision in the transit depth of $\approx$140 ppm in 15 nm bins, although the precision varies significantly over the wavelength range. | result 0.90 | 0.96 | 0.02 | asserted 1.00 |
| s4 | Our FORS2 observations confirm the cloud-deck previously inferred using HST/STIS. | result 1.00 | 0.90 | 0.23 | asserted 1.00 |
| s5 | We also re-analyse the HST/STIS data using a Gaussian process model, finding excellent agreement with earlier measurements. | result 0.40 | 0.95 | 0.05 | asserted 1.00 |
| s6 | We reproduce the Rayleigh scattering signature at short wavelengths ($\lesssim$5300 $\AA$) and the cloud-deck at longer wavelengths. | result 0.99 | 0.93 | 0.25 | asserted 1.00 |
| s7 | However, our FORS2 observations appear to rule out the large potassium feature previously detected using STIS, yet it is recovered from the HST/STIS data, although with reduced amplitude and significance ($\approx$2.5$\sigma$). | result 1.00 | 0.89 | 0.49 | hedged possibility 0.86 |
| s8 | The discrepancy between our results and the earlier STIS detection of potassium ($\approx$4.3$\sigma$) is either a result of telluric contamination of the ground-based observations, or an underestimate of the uncertainties for narrow-band features in HST/STIS when using linear basis models to account for the systematics. | interpretation 0.99 | 0.47 | 0.17 | hedged possibility 0.92 |
| s9 | Our results further demonstrate the use of ground-based multi-object spectrographs for the study of exoplanet atmospheres, and highlight the need for caution in our interpretation of narrow-band features in low-resolution spectra of hot-Jupiters. | interpretation 0.89 | 0.51 | 0.19 | asserted 1.00 |
What was examined, and what was not
- arXiv listing abstract v1
- full text
- figures and tables
- references and citing sentences
- relations to other papers
- P abstract
- S sections
- T body sentences
- C citations
- R cross-paper relations
The paper
Original abstract
We present transmission spectroscopy of the hot-Jupiter WASP-31b using FORS2 on the VLT during two primary transits. The observations cover a wavelength range of $\approx$400-840nm. The light curves are corrupted by significant systematics, but these were to first order invariant with wavelength and could be removed using a common-mode correction derived from the white light curves. We reach a precision in the transit depth of $\approx$140 ppm in 15 nm bins, although the precision varies significantly over the wavelength range. Our FORS2 observations confirm the cloud-deck previously inferred using HST/STIS. We also re-analyse the HST/STIS data using a Gaussian process model, finding excellent agreement with earlier measurements. We reproduce the Rayleigh scattering signature at short wavelengths ($\lesssim$5300 $\AA$) and the cloud-deck at longer wavelengths. However, our FORS2 observations appear to rule out the large potassium feature previously detected using STIS, yet it is recovered from the HST/STIS data, although with reduced amplitude and significance ($\approx$2.5$\sigma$). The discrepancy between our results and the earlier STIS detection of potassium ($\approx$4.3$\sigma$) is either a result of telluric contamination of the ground-based observations, or an underestimate of the uncertainties for narrow-band features in HST/STIS when using linear basis models to account for the systematics. Our results further demonstrate the use of ground-based multi-object spectrographs for the study of exoplanet atmospheres, and highlight the need for caution in our interpretation of narrow-band features in low-resolution spectra of hot-Jupiters.
Human review
How the literature uses it
1 arXiv paper cite this in 3 sentences
Papers citing it · 2 sentences without a confident label
Uses its method or tool 1 paper
-
As one looks for relative variations of transit depth in transmission spectroscopy, these spectral light curves are corrected for the common mode systematics that are present across all the channels [ref] .
Probing the atmosphere of a sub-Jovian planet orbiting a cool dwarf · Spectral light curves · 0.91
What it cites
Cites as background 1 paper
-
Space-based observations have led the way in our understanding of exoplanet atmospheres [ref] , however ground-based observations are rapidly increasing in importance, with the adoption of multi-object spectrographs (MOS) to perform differential spectro-photometry [ref] .
Rayleigh scattering in the transmission spectrum of HAT-P-18b · Introduction · 0.93
Discussion
Know something about this paper? Leave a comment, or highlight any passage above to comment on it.