The linearly polarized emission from SgrA* changes in character during flaring activity, and these changes may be due to orbiting hot-spots in the accretion flow. Using models that include radiative transfer through the plasma close to the black hole, 1.3mm VLBI data sets are simulated. By comparing parallel hand fringes (i.e. LCP-LCP) with cross hand fringes (RCP-LCP) one can search for periodic signatures of material orbiting the black hole.
Fish, Doeleman, Broderick, Loeb, Rogers, ApJ, v706, p. 1353-1363 (2009), "Detecting Changing Polarization Structures in Sagittarius A* with High Frequency VLBI"
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| First polarimetric 1.3mm VLBI observations on the Arizona-Hawaii Baseline. (Top) Parallel-hand (LCP-LCP) detection of 1924-292 between the SMT (10m) dish on Mt. Graham, AZ and a phased array combining the SMA and JCMT on Mauna Kea into a single VLBI element. These detections on quasar 1924-292 demonstrate the capability, and increases in sensitivity will soon enable similar detections on SgrA*. |
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| Simulated observerations of a polarized hot spot:Simulated ratio of RCP-LCP amplitude to LCP-LCP amplitude, showing the expected periodicity due to an orbiting hot-spot in the accretion flow. The period corresponds to the Innermost Stable Circular Orbit (ISCO) of a 4 million solar mass black hole. Black points are 10 second integrations on the baseline between phased ALMA and the South Pole Telescope. |
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