A helium P-Cygni profile in RR Lyrae stars? D. Gillet, F. L. Sefyani, A. Benhida, N. Fabas, P. Mathias, Z. Benkhaldoun and A. Daassou A&A, 587 (2016) A134 Published online: 02 March 2016 DOI: 10.1051/0004-6361/201527287