The Mantis Network I: A standard grid of templates and masks for cross-correlation analyses of ultra-hot Jupiter transmission spectra

Abstract

The atmospheres of ultra-hot Jupiters are highly interesting and unique chemical laboratories. Due to the very high atmospheric temperatures, formation of aerosols is unlikely on their day-sides. Furthermore, molecules usually present in atmospheres of other extrasolar gas giants are mostly dissociated, yielding a chemical composition dominated by atoms and ions instead. Thus, these planets offer the potential of detailed chemical characterisation by directly detecting elements through high-resolution day-side and transit spectroscopy. This allows, in principle, to directly infer the element abundances of these objects, which may provide crucial constraints on their formation process and evolution history. In atmospheres of cooler planets, deriving metallicities is much more complicated because elements are usually bound in a multitude of molecules or even condensates. In the recent past, several chemical species, mostly in the form of atoms and ions, have already been detected using high-resolution spectroscopy in combination with the cross-correlation technique. With this study, we provide a grid of standard templates designed to be used together with the cross-correlation method. This allows for straightforward detection of chemical species in the atmospheres of hot extrasolar planets. In total, we calculate high-resolution templates for more than 140 different species across several atmospheric temperatures. In addition to the high-resolution templates, we also provide line masks that just include the position of line peaks and their absorption depths relative to the spectral continuum. A separate version of these line masks also takes potential blending effects with lines of other species into account. All templates and line masks are publicly available on the CDS data server.

Transmission spectroscopy of the ultra-hot Jupiter MASCARA-4 b

“…Previous studies of individual UHJs use cross-correlation templates that are modeled differently. A standard set of models such as presented in Kitzmann et al (2021) will be beneficial if it can be commonly used in such analyses. Yet the choice of temperature in the model affects the relative weights assigned to weak versus strong lines, which changes the amplitude of CCFs by up to a factor of two.…”

Detection of barium in the atmospheres of the ultra-hot gas giants WASP-76b and WASP-121b

“…After the planetary transmission spectrum was retrieved for each of the exposures, we performed a cross-correlation anal- ysis with all the templates from The Mantis Network I 7 (Kitzmann et al 2021). These templates allow for the use of individual lines that would otherwise go unnoticed due to the high noise in the retrieved planetary spectrum.…”

“…By using the cross-correlation function (CCF) approach, these individual lines can be combined into a detectable line profile. For the WASP-76b and WASP-121b line mask, we considered an isothermal atmosphere at 2500 K 8 because of the equilibrium temperatures of the two planets (West et al 2016;Delrez et al 2016) and in line with the application outlined in Kitzmann et al (2021). The number of lines used per species in our wavelength range is listed in Appendix E.…”