THE ENVIRONMENT AND DISTRIBUTION OF EMITTING ELECTRONS AS A FUNCTION OF SOURCE ACTIVITY IN MARKARIAN 421

Journal Article · Fri May 20 00:00:00 EDT 2011 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/733/1/14· OSTI ID:21576828

Mankuzhiyil, Nijil ^[1]; Ansoldi, Stefano ^[2]; Persic, Massimo ^[3]; Tavecchio, Fabrizio ^[4]

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1. Department of Physics, Udine University, via Delle Scienze 208, I-33100 Udine (Italy)
2. International Center for Relativistic Astrophysics (ICRA), c/o Dipartimento di Fisica, P.le Aldo Moro 5, I-00185 Roma (Italy)
3. INAF-Trieste, via G. B. Tiepolo 11, I-34143 Trieste (Italy)
4. INAF-Brera, via E. Bianchi 46, I-23807 Merate (Italy)

For the high-frequency-peaked BL Lac object Mrk 421, we study the variation of the spectral energy distribution (SED) as a function of source activity, from quiescent to active. We use a fully automatized {chi}{sup 2}-minimization procedure, instead of the 'eyeball' procedure more commonly used in the literature, to model nine SED data sets with a one-zone synchrotron self-Compton (SSC) model and examine how the model parameters vary with source activity. The latter issue can finally be addressed now, because simultaneous broadband SEDs (spanning from optical to very high energy photon) have finally become available. Our results suggest that in Mrk 421 the magnetic field (B) decreases with source activity, whereas the electron spectrum's break energy ({gamma}{sub br}) and the Doppler factor ({delta}) increase-the other SSC parameters turn out to be uncorrelated with source activity. In the SSC framework, these results are interpreted in a picture where the synchrotron power and peak frequency remain constant with varying source activity, through a combination of decreasing magnetic field and increasing number density of {gamma} {<=} {gamma}{sub br} electrons: since this leads to an increased electron-photon scattering efficiency, the resulting Compton power increases, and so does the total (= synchrotron plus Compton) emission.

• OSTI ID: 21576828
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 733; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
BL LACERTAE OBJECTS
COLLISIONS
COSMIC RADIO SOURCES
DISTRIBUTION
ELECTROMAGNETIC RADIATION
ELECTRON COLLISIONS
ELECTRON SPECTRA
ELECTRONS
ELEMENTARY PARTICLES
ENERGY SPECTRA
FERMIONS
GAMMA RADIATION
INTERACTIONS
IONIZING RADIATIONS
LEPTONS
MAGNETIC FIELDS
PARTICLE INTERACTIONS
PHOTON COLLISIONS
PHOTON-ELECTRON COLLISIONS
PHOTON-ELECTRON INTERACTIONS
PHOTON-LEPTON INTERACTIONS
RADIATIONS
SPECTRA
VARIATIONS