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Renewed Activity in the Galactic Black Hole IGR J17091-3624

ATel #8742; J. M. Miller, M. Reynolds (Michigan), J. Kennea (Swift/PSU), A. L. King (Stanford), J. Tomsick (UC Berkeley)
on 26 Feb 2016; 18:55 UT
Credential Certification: Jon Miller (jonmm@umich.edu)

Subjects: X-ray, Binary, Black Hole, Transient

Referred to by ATel #: 8761, 8795, 8821, 8834, 8858

IGR J17091-3624 is a remarkable black hole transient. It displays the rich set of peculiar "states" and X-ray QPOs observed in GRS 1915+105 (Altamirano et al. 2011, Altamirano & Belloni 2012). High-resolution X-ray spectroscopy has revealed an ultra-fast disk wind (0.03-0.05c, King et al. 2012).

Following a steady rise in the Swift/BAT, we requested a 1 ks snapshot with the XRT. The observation started on 2016 Feb. 26 at 00:44:39 UT. The source is strongly detected, with nearly 1300 photons accumulated in 0.98 ks. The "photon counting" mode spectrum is piled-up (and weak mirror arcs from a nearby source affect the image in a minor way). A power-law as hard as Gamma = 1.3-1.4 is a reasonable fit to the XRT spectrum and suggests a flux of approximately 2 E-10 erg/cm^2/s (0.3-10.0 keV).

Observations in all bands are encouraged.

We thank the Swift PI and team for quickly observing IGR J17091-3624.

Altamirano, D., et al., 2011, ApJ, 742, L17
Altamirano, D., Belloni, T., 2012, ApJ, 747, L4
King, A. L., et al., 2012, 746, L20