A bright flare in the obscured state of GRS 1915+105 as seen by NICER and Swift

We report time-resolved NICER and Swift X-ray spectroscopy of a bright flare from the black hole X-ray binary GRS 1915+105 during its obscured state, which is characterized by heavy line-of-sight absorption by dense material with complex geometry. In April 2023, an unexpected flare was detected, with the observed X-ray flux increasing by nearly an order of magnitude relative to the typical obscured-state level. The spectra show pronounced variability, including significant evolution of the Fe K emission features. Time-resolved spectral modeling indicates that the main flare is associated with a combination of enhanced intrinsic emission and reduced obscuration. We further find that neutral and ionized reflection components are subject to distinct absorbers, whose evolving visibility implies a stratified absorber-reflector geometry. These properties are consistent with a re-illumination phase following a failed disk wind. A delayed radio flare detected about 2.5 days later suggests a coupling between accretion and jet activity.

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