High-resolution Transmission Spectroscopy of Ultrahot Jupiter WASP–33b with NEID

Abstract

We report an attempt to detect molecular and atomic species in the atmosphere of the ultrahot Jupiter WASP-33b using the high-resolution echelle spectrograph NEID with a wavelength coverage of 380–930 nm. By analyzing the transmission spectrum of WASP-33b using the line-by-line technique and the cross-correlation technique, we confirm previous detection of Hα, Hβ, Hγ, and Ca ii infrared triplets. We find no evidence for a significant day-to-night wind in WASP-33b, taking into account the effects of stellar pulsations using a relatively novel Gaussian process method and poorly constrained systemic velocity measurements. We also detect the previously reported pretransit absorption signal, which may be a pulsation mode induced by the planet. Combined with previous CARMENES and HARPS-N observations, we report the nondetection of TiO, Ti i, and V i in the transmission spectrum, while they were already detected in the dayside atmosphere of WASP-33b. This implies a difference in the chemical compositions and abundances between the dayside and terminator atmospheres of WASP-33b and certainly requires further improvements in the sensitivity of the detection methods.