Time-resolved XRISM Spectroscopy Reveals the Evolution and Structure of the Corona in MCG-6-30-15

We present a time-resolved analysis of high-resolution spectra of the active galactic nucleus MCG-6-30-15 obtained by XRISM, alongside broadband spectra from NuSTAR and XMM - Newton during a coordinated observing campaign in 2024 February. These observations provide some of the most detailed measurements of X-ray reflection from the innermost regions of the accretion disk around a supermassive black hole, as well as its evolution during periods of significant variability. We find that both the X-ray spectrum and its variability can be described by a self-consistent model of the reflection of coronal X-ray emission from the accretion disk around a rapidly spinning ( a ⋆ > 0.93) black hole, in which the observed variability arises from underlying changes in the luminosity, spatial extent, and motion of the corona. While the corona is compact, residing within 10 r g of the black hole for the majority of the observations, finite spatial extent is required to fully explain the shape of the reflection spectrum. A flare was observed in the X-ray emission during which the corona expanded to around 15 r g and was accelerated away from the black hole, reaching a velocity of 0.27 c . Around the flare, short dips in the flux were observed, during which the corona was found to have collapsed into a confined region within 2.5 r g of the black hole, enhancing the relativistic effects observed from the inner accretion disk. We find it necessary to account for such significant spectral variability in order to obtain accurate measurements of the black hole spin via X-ray reflection spectroscopy.