Empirical mass-loss rates and clumping properties of Galactic early-type O supergiants C. Hawcroft, H. Sana, L. Mahy, J. O. Sundqvist, M. Abdul-Masih, J. C. Bouret, S. A. Brands, A. de Koter, F. A. Driessen and J. Puls A&A, 655 (2021) A67 Published online: 18 November 2021 DOI: 10.1051/0004-6361/202140603