Presentation #105A.01 in the session Stellar & Compact Objects I.
IGR J17091-3624 is the only black hole X-ray binaries (BHXB) that exhibits exotic “heartbeat”-like variability in its X-ray light curve besides GRS 1915+105. It can be seen as a bridge between the most peculiar BHXB GRS 1915+105 and “normal” BHXBs, because it alternates the conventional and exotic behaviour of BHXBs. Recently, IGR J17091-3624 went into outburst for the first time in the NICER/NuSTAR era. These exquisite data allow us to simultaneously track the exotic variability and the corresponding spectral features with unprecedented detail. The observations cover the traditional initial hard state, intermediate state, and an exotic soft state where we see two heartbeat-like classes and one quiet class. States without heartbeats show broad iron line emission due to relativistic reflection, and states exhibiting heartbeats show absorption features from highly ionized wind. We see evidence that the wind is not radiatively driven, and the heartbeat is not produced by a high Eddington ratio alone. This legacy dataset presents crucial constraints on our understanding of accretion-ejection connection in accreting black holes.