X-ray Polarization from Black Holes: GEMS Scientific White Paper

Understand

We present here a summary of the scientific goals behind the Gravity and Extreme Magnetism SMEX (GEMS) X-ray polarimetry mission's black hole (BH) observing program.

• The primary targets can be divided into two classes: stellar-mass galactic BHs in accreting binaries, and super-massive BHs in the centers of active galactic nuclei (AGN).
• The stellar-mass BHs can in turn be divided into various X-ray spectral states: thermal-dominant (disk), hard (radio jet), and steep power-law (hot corona).
• These different spectral states are thought to be generated by different accretion geometries and emission mechanisms.