Detection of ionized calcium in the atmosphere of the ultra-hot Jupiter KELT-9b

German Max-Planck Gesellschaft (MPG); Spanish Consejo Superior de Investigaciones Cientificas (CSIC) Consejo Superior de Investigaciones Cientificas (CSIC); European Union through FEDER/ERF [FICTS-2011-02]; CARMENES Consortium; Spanish Ministry of Science Spanish Government; German Science Foundation (DFG) German Research Foundation (DFG); Klaus Tschira Stiftung; states of Baden-Wurttemberg and Niedersachsen; Junta de Andalucia Junta de Andalucia; NIST's Standard Reference Data Program (SRDP); NIST's Systems Integration for Manufacturing Applications (SIMA) Program