Is there a Black Hole in any of the INTEGRAL HMXBs?

Through its hard X-ray survey of the Galactic Plane, INTEGRAL has uncovered large numbers of HMXBs, and many of them have not been well-studied to date. We propose to observe two INTEGRAL HMXBs that have not previously shown signatures of having a neutron star: IGR J18214-1318 and IGR J08262-3736. With XMM-Newton and NuSTAR, we will search for such signatures (pulsations, cyclotron lines, exponential cutoffs with e-folding energies below ~20 keV). If these features are lacking and if the source instead has a power-law that extends to the top of the NuSTAR bandpass, this would be an excellent black hole candidate and motivation would be very strong for follow-up optical or IR spectroscopy to determine the mass of the compact object.