Mining the Ultrahot Skies of HAT-P-70b: Detection of a Profusion of Neutral and Ionized Species

With an equilibrium temperature above 2500 K, the recently discovered HAT-P-70b belongs to a new class of exoplanets known as ultrahot Jupiters: extremely irradiated gas giants with day-side temperatures that resemble those found in stars. These ultrahot Jupiters are among the most amenable targets for follow-up atmospheric characterization through transmission spectroscopy. Here, we present the first analysis of the transmission spectrum of HAT-P-70b using high-resolution data from the HARPS-N spectrograph of a single-transit event. We use a cross-correlation analysis and transmission spectroscopy to look for atomic and molecular species in the planetary atmosphere. We detect absorption by Ca II, Cr I, Cr II, Fe I, Fe II, H I, Mg I, Na I, and V I, and we find tentative evidence of Ca I and Ti II. Overall, these signals appear blueshifted by a few km s(-1), suggestive of winds flowing at high velocity from the day side to the night side. We individually resolve the Ca II H and K lines, the Na I doublet, and the H-alpha, H-beta, and H-gamma Balmer lines. The cores of the Ca II and H I lines form well above the continuum, indicating the existence of an extended envelope. We refine the obliquity of this highly misaligned planet to 107.9(-1.7)(+2.0) degrees by examining the Doppler shadow that the planet casts on its A-type host star. These results place HAT-P-70b as one of the exoplanets with the highest number of species detected in its atmosphere.

Automated summary

HAT-P-70b is an ultrahot Jupiter with extremely high radiation and temperatures similar to stars. Its atmosphere contains multiple atomic and molecular species, which show a blueshift, suggesting high-velocity winds from the day side to the night side.