Parameter constraints in a near-equipartition model with multifrequency NuSTAR, Swift, and Fermi-LAT data from 3C 279
Abstract
Precise spectra of 3C 279 in the 0.5-70 keV range, obtained during two epochs of Swift and NuSTAR observations, are analysed using a near-equipartition model. We apply a one-zone leptonic model with a three-parameter log-parabola electron energy distribution to fit the Swift and NuSTAR X-ray data, as well as simultaneous optical and Fermi-LAT gamma-ray data. The Markov chain Monte Carlo technique is used to search the high-dimensional parameter space and evaluate the uncertainties on model parameters. We show that the two spectra can be successfully fitted in near-equipartition conditions, defined by the ratio of the energy density of relativistic electrons to magnetic field ζe being close to unity. In both spectra, the observed X-rays are dominated by synchrotron self-Compton photons, and the observed gamma-rays are dominated by Compton scattering of external infrared photons from a surrounding dusty torus. Model parameters are well constrained. From the low state to the high state, both the curvature of the log-parabola width parameter and the synchrotron peak frequency significantly increase. The derived magnetic fields in the two states are nearly identical (∼1 G), but the Doppler factor in the high state is larger than that in the low state (∼28 versus ∼18). We derive that the gamma-ray emission site takes place outside the broad-line region, at ≳0.1 pc from the black hole, but within the dusty torus. Implications for 3C 279 as a source of high-energy cosmic rays are discussed.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- December 2015
- DOI:
- 10.1093/mnras/stv2091
- arXiv:
- arXiv:1509.04945
- Bibcode:
- 2015MNRAS.454.1310Y
- Keywords:
-
- radiation mechanisms: non-thermal;
- galaxies: jets;
- gamma-rays: galaxies;
- Astrophysics - High Energy Astrophysical Phenomena;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- accepted by MNRAS