4U 1909+07: a well-hidden pearlF. Fürst, I. Kreykenbohm, S. Suchy, L. Barragán, J. Wilms, R. E. Rothschild and K. PottschmidtA&A, 525 (2011) A73DOI: https://doi.org/10.1051/0004-6361/201015636