A Spectral Survey of WASP-19b with ESPRESSO

Abstract

High resolution precision spectroscopy provides a multitude of robust techniques for probing exoplanetary atmospheres. We present multiple VLT/ESPRESSO transit observations of the hot-Jupiter exoplanet WASP-19b with previously published but disputed atmospheric features from low resolution studies. Through spectral synthesis and modeling of the Rossiter-McLaughlin (RM) effect we calculate stellar, orbital and physical parameters for the system. From narrow-band spectroscopy we do not detect any of H I, Fe I, Mg I, Ca I, Na I and K I neutral species, placing upper limits on their line contrasts. Through cross correlation analyses with atmospheric models, we do not detect Fe I and place a 3σ upper limit of log (XFe/X⊙) ≈ −1.83 ± 0.11 on its mass fraction, from injection and retrieval. We show the inability to detect the presence of H2O for known abundances, owing to lack of strong absorption bands, as well as relatively low S/N ratio. We detect a barely significant peak (3.02 ± 0.15 σ) in the cross correlation map for TiO, consistent with the sub-solar abundance previously reported. This is merely a hint for the presence of TiO and does not constitute a confirmation. However, we do confirm the presence of previously observed enhanced scattering towards blue wavelengths, through chromatic RM measurements, pointing to a hazy atmosphere. We finally present a reanalysis of low resolution transmission spectra of this exoplanet, concluding that unocculted starspots alone cannot explain previously detected features. Our reanalysis of the FORS2 spectra of WASP-19b finds a ∼ 100× sub-solar TiO abundance, precisely constrained to log XTiO ≈ −7.52 ± 0.38, consistent with the TiO hint from ESPRESSO. We present plausible paths to reconciliation with other seemingly contradicting results.

Detection of Aerosols at Microbar Pressures in an Exoplanet Atmosphere

“…13. Planets with high irradiation levels of FEUV, such as WASP-19b, show evidence of a slope towards the blue (Sing et al 2016;Sedaghati et al 2017Sedaghati et al , 2021 but covering less scale heights than the spectra in WASP-69b. These observations lead to another question: if photochemical haze produces the Rayleigh scattering observed in WASP-69b, why is it probing more scale heights in this planet than in other observations of more strongly irradiated planets?…”

A survey of sodium absorption in ten giant exoplanets with high-resolution transmission spectroscopy

“…Over the last few years, the issues caused by low flux in the cores of deep stellar lines has become a well known problem and the weighted average approach is now commonly employed for highresolution transmission spectroscopy (e.g. Allart et al 2020;Chen et al 2020b;Borsa et al 2021;Sedaghati et al 2021). Since there is a difference between the weighted and unweighted results for two planets in this survey (HD 189733 b and WASP-49b), performing a homogeneous analysis is important when comparing the extent of sodium absorption across the sample of exoplanets.…”

“…In recent work, assigning weights to the spectra before combining (e.g. Allart et al 2020;Chen et al 2020b;Borsa et al 2021;Sedaghati et al 2021) or ignoring data in regions where the planetary signal overlaps with the location of the stellar line cores (Seidel et al 2020b,c) has proved to be effective at nullifying these effects.…”

TRIDENT: A Rapid 3D Radiative Transfer Model for Exoplanet Transmission Spectra

“…Since our cross section database (Appendix C) is precomputed at R ∼ 10 6 (see Section 3.3), TRIDENT can therefore generate template spectra for high-resolution cross correlation analyses (e.g. Snellen et al 2010;Hoeijmakers et al 2018;Sedaghati et al 2021). Future improvements to TRIDENT can focus on physical effects that manifest in high-resolution transmission spectra, including planetary rotation and winds (e.g.…”