Testing the Stochastic Acceleration Model for Flares in Sagittarius A*

Siming Liu(1), Vahé Petrosian(2), Fulvio Melia(3,4), and Christopher L. Fryer(1,5)

(1) Los Alamos National Laboratory, Los Alamos, NM 87545
(2) Center for Space Science and Astrophysics, Department of Physics and Applied Physics, Stanford University, Stanford, CA 94305
(3) Physics Department and Steward Observatory, The University of Arizona, Tucson, AZ 85721
(4) Sir Thomas Lyle Fellow and Miegunyah Fellow.
(5) Physics Department, The University of Arizona, Tucson, AZ 85721

Paper: ApJL, submitted

EPrint Server: astro-ph/0603136


The near-IR and X-ray flares in Sagittarius A* are believed to be produced by relativistic electrons via synchrotron and synchrotron self-Comptonization (SSC), respectively. These electrons are likely energized by turbulent plasma waves through second order Fermi acceleration that, in combination with the radiative cooling processes, produces a relativistic Maxwellian distribution in the steady state. This model has four principal parameters, namely the magnetic field B, the electron density n, their ``temperature'' gamma c me c2, and the size of the flare region R. In the context of stochastic acceleration by plasma waves, the quantities R n1/2 B and gamma c R n should remain nearly constant in time. Therefore, simultaneous spectroscopic observations in the NIR and X-ray bands can readily test the model, which, if proven to be valid, may be used to determine the evolution of the plasma properties during an eruptive event with spectroscopic observations in either band or simultaneous flux density measurements in both bands. The formulation we develop here may also be applicable to other sources radiating via thermal synchrotron and SSC processes.

Preprints available from the authors at liusm@lanl.gov , or the raw TeX (no figures) if you click here.

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