dc.contributor.author | Gibson, NP | |
dc.contributor.author | Nokolov, N | |
dc.contributor.author | Sing, DK | |
dc.contributor.author | Barstow, J | |
dc.contributor.author | Evans, TE | |
dc.contributor.author | Kataria, T | |
dc.contributor.author | Wilson, PA | |
dc.date.accessioned | 2017-03-06T14:41:20Z | |
dc.date.issued | 2017-0211 | |
dc.description.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 ≈400–840 nm. The light curves are corrupted by significant systematics, but these
were to first order invariant with wavelength and could be removed using a commonmode
correction derived from the white light curves. We reach a precision in the
transit depth of ≈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 (. 5300 ˚A) 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 (≈ 2.5σ). The
discrepancy between our results and the earlier STIS detection of potassium (≈ 4.3σ) 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. | en_GB |
dc.description.sponsorship | This work is based on observations collected at the European
Organisation for Astronomical Research in the Southern
Hemisphere under ESO programme 096.C-0765. N. P.
G. gratefully acknowledges support from the Royal Society
in the form of a University Research Fellowship. N. N, D. K.
S, and T. M. E. acknowledge funding from the European Research
Council under the European Unions Seventh Framework
Programme (FP7/2007-2013) / ERC grant agreement
no. 336792. J. K. B. is supported by a Royal Astronomical
Society Research Fellowship. P.A.W. acknowledges the
support of the French Agence Nationale de la Recherche
(ANR), under program ANR-12-BS05-0012 ‘Exo-Atmos’.
We are grateful to the developers of the NumPy, SciPy,
Matplotlib, iPython and Astropy packages, which were
used extensively in this work (Jones et al. 01 ; Hunter 2007;
P´erez & Granger 2007; Astropy Collaboration et al. 2013). | en_GB |
dc.identifier.citation | Vol. 67 (4), pp. 4591-4605 | en_GB |
dc.identifier.doi | 10.1093/mnras/stx353 | |
dc.identifier.uri | http://hdl.handle.net/10871/26254 | |
dc.language.iso | en | en_GB |
dc.publisher | Oxford University Press (OUP) / Royal Astronomical Society | en_GB |
dc.subject | methods: data analysis | en_GB |
dc.subject | stars: individual (WASP-31) | en_GB |
dc.subject | planetary systems | en_GB |
dc.subject | techniques: spectroscopic | en_GB |
dc.subject | techniques: Gaussian processes | en_GB |
dc.title | VLT/FORS2 comparative transmission spectroscopy II: confirmation of a cloud-deck and Rayleigh scattering in WASP-31b, but no potassium? | en_GB |
dc.type | Article | en_GB |
dc.identifier.issn | 1365-2966 | |
dc.description | This is the author accepted manuscript. The final version is available from OUP via the DOI in this record. | en_GB |
dc.identifier.journal | Monthly Notices of the Royal Astronomical Society | en_GB |