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J/MNRAS/446/2428 WASP-31b:HST/Spitzer transmission spectral survey (Sing+, 2015)

HST hot-Jupiter transmission spectral survey: detection of potassium in WASP-31b along with a cloud deck and Rayleigh scattering. Sing D.K., Wakeford H.R., Showman A.P., Nikolov N., Fortney J.J., Burrows A.S., Ballester G.E., Deming D., Aigrain S., Desert J.-M., Gibson N.P., Henry G.W., Knutson H., Lecavelier des Etangs A., Pont F., Vidal-Madjar A., Williamson M.W., Wilson P.A. <Mon. Not. R. Astron. Soc., 446, 2428-2443 (2015)> =2015MNRAS.446.2428S (SIMBAD/NED BibCode)
ADC_Keywords: Models, atmosphere ; Stars, double and multiple ; Planets ; Spectroscopy Keywords: techniques: spectroscopic - planets and satellites: atmospheres - planets and satellites: individual: WASP-31b - stars: individual: WASP-31 - planetary systems Abstract: We present Hubble Space Telescope optical and near-IR transmission spectra of the transiting hot-Jupiter WASP-31b. The spectrum covers 0.3-1.7 µm at a resolution R∼70, which we combine with Spitzer photometry to cover the full-optical to IR. The spectrum is dominated by a cloud deck with a flat transmission spectrum which is apparent at wavelengths >0.52µm. The cloud deck is present at high altitudes and low pressures, as it covers the majority of the expected optical Na line and near-IR H2O features. While Na I absorption is not clearly identified, the resulting spectrum does show a very strong potassium feature detected at the 4.2σ confidence level. Broadened alkali wings are not detected, indicating pressures below ∼10 mbar. The lack of Na and strong K is the first indication of a sub-solar Na/K abundance ratio in a planetary atmosphere (ln[Na/K]=-3.3±2.8), which could potentially be explained by Na condensation on the planet's night side, or primordial abundance variations. A strong Rayleigh scattering signature is detected at short wavelengths, with a 4σ significant slope. Two distinct aerosol size populations can explain the spectra, with a smaller sub-micron size grain population reaching high altitudes producing a blue Rayleigh scattering signature on top of a larger, lower lying population responsible for the flat cloud deck at longer wavelengths. We estimate that the atmospheric circulation is sufficiently strong to mix micron size particles upwards to the required 1-10 mbar pressures, necessary to explain the cloud deck. These results further confirm the importance of clouds in hot Jupiters, which can potentially dominate the overall spectra and may alter the abundances of key gaseous species. Description: We observed two transits of WASP-31b with the HST STIS G430L grating during 2012 June 13 and 26, as well as one transit with the STIS G750L during 2012 July 10. In addition to the STIS data, observations of WASP-31b were also conducted in the infrared with WFC3 on the HST. Observations began on 2012 May 13 at 12:53 using the IR G141 grism in forward spatial scan mode over five HST orbits. We analyse two transit observations obtained using the Infrared Array Camera (IRAC) instrument (Programme 90092 with P.I. Desert) on the Spitzer space telescope in the 3.6 µm and 4.5 µm channels in subarray mode (32x32 pixel, or 39 centred on the planets host). The 3.6 µm observation was performed on UT 2013 March 9 (between 06:59 and 11:37) and the 4.5 observation was performed on UT 2013 March 19 (between 12:19 and 16:58). Objects: -------------------------------------------------- RA (ICRS) DE Designation(s) -------------------------------------------------- 11 17 45.36 -19 03 17.2 WASP-31b = WASP-31b -------------------------------------------------- File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table3.dat 58 63 WASP-31b broad-band transmission spectral results and non-linear limb-darkening coefficients for the STIS G430L, G750L, WFC3 G141, and Spitzer IRAC.
See also: J/A+A/428/1001 : Non-linear limb-darkening law for LTE models. III. (Claret, 2004) J/A+A/531/A60 : WASP-31b photometry and radial velocities (Anderson+, 2011) J/A+A/552/A16 : Limb-darkening for CoRoT, Kepler, Spitzer. II. (Claret+, 2013) J/MNRAS/456/1294 : Limb-darkening coefficients (Reeve+, 2016) Byte-by-byte Description of file: table3.dat
Bytes Format Units Label Explanations
1- 5 I5 0.1nm Lambda1 Lower value of wavelength interval (Å) 7- 11 I5 0.1nm Lambda2 ? Upper value of wavelength interval (Å) 13- 19 F7.5 --- Rp/R* Planet-to-star radius ratio 21- 27 F7.5 --- r_Rp/R* Uncertainty in Rp/R* 29- 34 F6.4 --- c1 Non-linear limb-darkening coefficient for the HST STIS G430L 36- 42 F7.4 --- c2 Non-linear limb-darkening coefficient for the HST STIS G750L 44- 50 F7.4 --- c3 Non-linear limb-darkening coefficient for the HST WFC3 G141 52- 58 F7.4 --- c4 Non-linear limb-darkening coefficient for the Spitzer IRAC
History: From electronic version of the journal
(End) Tiphaine Pouvreau [CDS] 02-Nov-2017
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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