On The Compatibility of Ground-based and Space-based Data: WASP-96 b, An Example

Abstract

<p>The study of exoplanetary atmosphere relies on detecting minute changes in the transit depth at different wavelengths. To date, a number of ground and space based instruments have been used to obtain transmission spectra of exoplanets in different waveband. One common practice is to combine observations from different instruments in order to achieve a broader wavelength coverage. We present here two inconsistent observations on WASP-96 b, one by Hubble Space Telescope (HST) and the other by Very Large Telescope (VLT). We present two key findings in our investigation: 1.) a strong water signature is detected via the HST WFC3 observations. 2.) A notable offset in transit depth (>1100 ppm) can be seen when the ground-based and space-based observations are combined together. The discrepancy raises the question of whether observations from different instruments could indeed be combined together. We attempt to align the observations by including an additional parameter in our retrieval studies but are unable to definitively ascertain that the aligned observations are indeed compatible. The case of WASP-96 b signals that compatibility of instruments should not be assumed. While wavelength overlaps between instruments can help, it should be noted that combining datasets remains a risky business. The difficulty in combining observations also strengthens the need for next generation instruments which will possess broader spectral coverage.</p>

Temperature and density dependence of line profiles of sodium perturbed by helium

“…This paper is a continuation of Allard et al (2007bAllard et al ( , 2019 where new K-H 2 and Na-H 2 collisional profiles have been presented using accurate ab initio potentials. These profiles are now used in many studies of brown dwarfs (e.g., Burningham et al 2017;Oreshenko et al 2020) and exoplanets (e.g., Phillips et al 2020;Hou Yip et al 2020;Gonzales et al 2021;Chubb et al 2021;Nikolov et al 2022;Samra et al 2023).…”