Journal Article

Polarized Gamma-Ray Emission from the Galactic Black Hole Cygnus X-1

Grinberg, V., Rodriguez, J., Laurent, P., Bel, M. Cadolle, Wilms, J., Pottschmidt, K.

2011

Overview

Because of their inherently high flux allowing the detection of clear signals, black hole x-ray binaries are interesting candidates for polarization studies, even if no polarization signals have been observed from them before. Such measurements would provide further detailed insight into these sources' emission mechanisms. We measured the polarization of the gamma-ray emission from the black hole binary system Cygnus X-1 with the International Gamma-Ray Astrophysics Laboratory Imager on Board the Integral Satellite (INTEGRAL/IBIS) telescope. Spectral modeling of the data reveals two emission mechanisms: The 250- to 400-keV (kilo-electron volt) data are consistent with emission dominated by Compton scattering on thermal electrons and are weakly polarized. The second spectral component seen in the 400-keV to 2-MeV band is by contrast strongly polarized, revealing that the MeV emission is probably related to the jet first detected in the radio band.

• Publisher: American Association for the Advancement of Science,The American Association for the Advancement of Science,American Association for the Advancement of Science (AAAS)
• Subject: Artificial satellites / Astronomy / Astrophysics / Binary and multiple stars / Black holes / Cygnus / Earth, ocean, space / Electrons / Emission measurements / Exact sciences and technology / gamma radiation / Gamma rays / Gamma-ray sources ; gamma-ray bursts / High Energy Astrophysical Phenomena / Photons / Physics / Polarization / radio / Radio jets / satellites / Sciences of the Universe / Signal detection / Stars / Stellar systems. Galactic and extragalactic objects and systems. The universe / Telescopes / Unidentified sources and radiation outside the solar system / X ray binary stars / X-radiation / X-ray binaries