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Matter and Electromagnetic Fields in Strong Gravity
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Matter and Electromagnetic Fields in Strong Gravity
CSIC Building (#406),
Seminar Room 4122.
Directions: home.cscamm.umd.edu/directions
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Probing Extreme Gravity with X-ray Polarization
Jeremy Schnittman
Johns Hopkins University
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Abstract:
In the coming years, new space missions may well be able to measure
X-ray polarization at levels of 1% or better in the ~1-10 keV energy
band. This region of the spectrum is critical for observing emission
from pulsars, X-ray binaries, supernova remnants, and AGN. In particular,
we propose that X-ray polarization may be an ideal tool for determining
the nature of black hole accretion disks surrounded by hot coronae. Using
a Monte Carlo radiation transport code in full general relativity, we
calculate the spectra and polarization features of these
black hole systems. At low energies, the signal is dominated by the
thermal flux coming directly from the optically thick disk. At higher
energy, the thermal seed photons have been inverse-Compton scattered
by the corona, often reflecting back off the disk before reaching the
observer, giving a distinctive polarization signature. By measuring
the degree and angle of this X-ray polarization, we can infer the
emission geometry of the accretion flow and in turn may be able to
determine the spin of the black hole.
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