Simultaneous X-ray and optical variability of M dwarfs observed with eROSITA and TESS W. M. Joseph, B. Stelzer, E. Magaudda and T. Vičánek Martínez A&A, 688 (2024) A49 Published online: 01 August 2024 DOI: 10.1051/0004-6361/202449405