Infrared He I 10830 Å, ultra-violet Ca II, and Mg II chromosphere emissions in the spectra of classical Cepheid X CygS. M. Andrievsky, V. V. Kovtyukh and S. A. KorotinA&A, 671 (2023) A27DOI: https://doi.org/10.1051/0004-6361/202245384