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 (𝑋 Fe /𝑋 ) ≈ −1.83 ± 0.11 on its mass fraction, from injection and retrieval. We show the inability to detect the presence of H 2 O 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 𝑋 TiO ≈ −7.52 ± 0.38, consistent with the TiO hint from ESPRESSO. We present plausible paths to reconciliation with other seemingly contradicting results.

TOI-1518b: A Misaligned Ultra-hot Jupiter with Iron in its Atmosphere

“…Fe may be especially difficult to detect in WASP-33b due to stellar pulsations. We acknowledge a few additional recent studies, including the non-detection Fe in WASP-19b (Sedaghati et al 2021) which is listed in Table 4 (however this target is considerably fainter than the others, at V = 12.3), a recent transmission spectroscopy study of HD149026b (Ishizuka et al 2021) (however the Fe signal was only at 2.8σ), and a non-detection in TOI-1431b (which orbits a relatively bright V = 8.0 star; this target is listed in Table 4).…”

Titanium oxide and chemical inhomogeneity in the atmosphere of the exoplanet WASP-189b

“…In the atmospheres of highly irradiated exoplanets, shortwave absorbers are predicted to be titanium oxide (TiO) and vanadium oxide (VO) 2 . Detections of TiO and VO have been claimed using both low [3][4][5][6] and high 7 spectral resolution observations, but later observations have failed to confirm these claims [8][9][10] or overturned them [11][12][13] . Here we report the unambiguous detection of TiO in the ultra-hot Jupiter WASP-189b 14 using high-resolution transmission spectroscopy.…”