Detection of Fe and evidence for TiO in the dayside emission spectrum of WASP-33b -- David Cont

We search for the signature of the thermal inversion agents TiO and Fe in the dayside emission spectrum of the ultra-hot Jupiter WASP-33b. The spectra were obtained with CARMENES and HARPS-N, covering different wavelength ranges. Telluric and stellar absorption lines were removed with SYSREM. We cross-correlated the residual spectra with model spectra to retrieve the signals from the planetary atmosphere. The emission signature of Fe is detected with both instruments at a significance level of 7.3 sigma. Evidence for TiO is found at 4.9 sigma with CARMENES, but no molecular signature is found with HARPS-N. An injection-recovery test suggests that the TiO signal is below the detection level at the wavelengths covered by HARPS-N. The TiO signal is located at Kp = 248 km/s, which disagrees with the Fe detection at Kp = 225 km/s. The Kp value for Fe agrees with prior investigations. We observe a broader line profile for Fe than for TiO. Our results confirm the presence of a temperature inversion layer in the planetary atmosphere. The observed Kp offset and different strengths of broadening in the line profiles suggest the existence of a TiO-depleted hot spot in the planetary atmosphere.