Iron line reveals hidden geometry of a stellar wind feeding a neutron star

X1908+075 pairs a massive star with a neutron star in a tight 4.4-day orbit. Using high-resolution X-ray spectra, researchers detected iron fluorescence that behaves unexpectedly: its brightness correlates with continuum flux but its equivalent width drops when absorption rises, opposite to the usual pattern in these systems. By modeling how absorption varies with orbital phase, they pinned down the system's inclination (46°) and the stellar wind mass-loss rate, revealing the neutron star feeds directly from the wind rather than through a disk.