A NOVEL APPROACH IN CONSTRAINING ELECTRON SPECTRA IN BLAZAR JETS: THE CASE OF Markarian 421
- Department of High Energy Astrophysics, Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA), 3-1-1 Yoshinodai, Sagamihara, 229-8510 (Japan)
- Stanford Linear Accelerator Center/KIPAC, 2575 Sand Hill Road, Menlo Park, CA 94025 (United States)
- Research Institute for Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555 (Japan)
- Astronomical Observatory, Jagiellonian University, ul. Orla 171, Krakow 30-244 (Poland)
We report results from the observations of the well-studied TeV blazar Mrk 421 with the Swift and the Suzaku satellites in 2008 December. During the observation, Mrk 421 was found in a relatively low activity state, with the corresponding 2-10 keV flux of 3 x 10{sup -10} erg s{sup -1} cm{sup -2}. For the purpose of robustly constraining the UV-to-X-ray emission continuum we selected only the data corresponding to truly simultaneous time intervals between Swift and Suzaku, allowing us to obtain a good-quality, broadband spectrum despite a modest length (0.6 ks) exposure. We analyzed the spectrum with the parametric forward-fitting SYNCHROTRON model implemented in XSPEC assuming two different representations of the underlying electron energy distribution, both well motivated by the current particle acceleration models: a power-law distribution above the minimum energy {gamma}{sub min} with an exponential cutoff at the maximum energy {gamma}{sub max}, and a modified ultra-relativistic Maxwellian with an equilibrium energy {gamma}{sub eq}. We found that the latter implies unlikely physical conditions within the blazar zone of Mrk 421. On the other hand, the exponentially moderated power-law electron distribution gives two possible sets of the model parameters: (1) flat spectrum dN'{sub e}/d{gamma} {proportional_to} {gamma}{sup -1.91} with low minimum electron energy {gamma}{sub min} < 10{sup 3}, and (2) steep spectrum {proportional_to}{gamma}{sup -2.77} with high minimum electron energy {gamma}{sub min} {approx_equal} 2 x 10{sup 4}. We discuss different interpretations of both possibilities in the context of a diffusive acceleration of electrons at relativistic, sub- or superluminal shocks. We also comment on exactly how the {gamma}-ray data can be used to discriminate between the different proposed scenarios.
- OSTI ID:
- 21474474
- Journal Information:
- Astrophysical Journal, Vol. 724, Issue 2; Other Information: DOI: 10.1088/0004-637X/724/2/1509; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
COSMOLOGY AND ASTRONOMY
ACCELERATION
BL LACERTAE OBJECTS
ELECTRON SPECTRA
ENERGY SPECTRA
GAMMA RADIATION
RELATIVISTIC RANGE
SATELLITES
TEV RANGE
X-RAY GALAXIES
COSMIC RADIO SOURCES
COSMIC RAY SOURCES
COSMIC X-RAY SOURCES
ELECTROMAGNETIC RADIATION
ENERGY RANGE
GALAXIES
IONIZING RADIATIONS
RADIATIONS
SPECTRA