Fermi-LAT Observations of Markarian 421: the Missing Piece of its Spectral Energy Distribution

By A. Abdo, M. Ackermann, M. Ajello, L. Baldini, J. Ballet, G. Barbiellini, D. Bastieri, K. Bechtol, R. Bellazzini, B. Berenji and 354 more. 2011

250 citations recorded by the source corpus.

We report on the gamma-ray activity of the high-synchrotron-peaked BL Lacertae object Mrk 421 during the first 1.5 years of Fermi operation, from 2008 August 5 to 2010 March 12. We find that the Large Area Telescope (LAT) gamma-ray spectrum above 0.3 GeV can be well-described by a power-law function with photon index Gamma=1.78 +/- 0.02 and average photon flux F(>0.3 GeV)=(7.23 +/- 0.16) x 10^{-8} ph cm^{-2} s^{-1}. Over this time period, the Fermi-LAT spectrum above 0.3 GeV was evaluated on 7-day-long time intervals, showing significant variations in the photon flux (up to a factor ~3 from the minimum to the maximum flux), but mild spectral variations. The variability amplitude at X-ray frequencies measured by RXTE/ASM and Swift/BAT is substantially larger than that in gamma-rays measured by Fermi-LAT, and these two energy ranges are not significantly correlated. We also present the first results from the 4.5-month-long multifrequency campaign on Mrk 421, which included the VLBA, Swift, RXTE, MAGIC, the F-GAMMA, GASP-WEBT, and other collaborations and instruments which provided excellent temporal and energy coverage of the source throughout the entire campaign (2009 January 19 to 2009 June 1). During this campaign, Mrk 421 showed a low activity at all wavebands. The extensive multi-instrument (radio to TeV) data set provides an unprecedented, complete look at the quiescent spectral energy distribution (SED) for this source. The broad band SED was reproduced with a leptonic (one-zone Synchrotron Self-Compton) and a hadronic model (Synchrotron Proton Blazar). Both frameworks are able to describe the average SED reasonably well, implying comparable jet powers but very different characteristics for the blazar emission site.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/b06c7f4bd971a29f3560f6ae9d7af6f49c953482

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

1. Bing Zhang
2. A. Marscher
3. M. Petropoulou
4. D. Giannios
5. L. Sironi
6. Y. Inoue
7. Anna Franckowiak
8. M. Tornikoski

In Nuclear and High Energy Physics

1. A. Marscher
2. M. Petropoulou
3. D. Giannios
4. L. Sironi
5. Y. Inoue
6. Anna Franckowiak
7. A. Reimer
8. A. Lähteenmäki

Citations in the corpus

• Simultaneous Planck, Swift, and Fermi observations of X-ray and γ-ray selected blazars (2011, background): “…out only rarely, and almost exclusively on the occasion of large flaring events in a few bright and well-known blazars, e.g., 3C 454.3 (Giommi et al. 2006; Abdo et al. 2009a; Vercellone et al. 2009), Mkn 421, (Donnarumma et al. 2009; Abdo et al. 2011), and PKS 2155−304 (Aharonian et al. 2009).”
• Relativistic Jets Shine through Shocks or Magnetic Reconnection (2015, background): “The high-energy component extends across the X-ray and γ-ray bands, with peak energy around 0.1 TeV, although this is not always clear (see, e.g., Abdo et al. 2011 for Mrk 421).”
• THE ORIGIN OF THE EXTRAGALACTIC GAMMA-RAY BACKGROUND AND IMPLICATIONS FOR DARK MATTER ANNIHILATION (2015, background): “…Finke et al. (2010), and use γa=1.7 and γb=2.6, which reproduces the long-term averaged spectra of bright BL Lacs with GeV-TeV measurements (RBS 0413, Mrk 421, Mrk 501, see Aliu et al. 2012; Abdo et al. 2011a,b) and those of bright FSRQs (like 3C 454.3, 3C 279, 3C 273, etc.) observed by Fermi-LAT.”
• The extragalactic background light and the gamma-ray opacity of the universe (2012, background): “…279, PKS 1510-08) and spectral hardening (1ES 0502+675) in the GeV regime (Abdo, A. A. et al., 2010), while the spectra of other blazars (Mrk 421, Abdo et al., 2011b), (Mrk 501, Abdo et al., 2011a) extend without any cutoff to 300 GeV (Abdo et al., 2010b), or multi-TeV energies (Krennrich et…”
• Kinematics of Parsec-scale Jets of Gamma-Ray Blazars at 43 GHz within the VLBA-BU-BLAZAR Program (2017, background): “…of the core was observed during the multi-wavelength outbursts in 2010 Spring and Autumn, with the maximum intrinsic brightness temperature of the core, Tb,int=1.65×1012, derived on 2010 October 24, which coincides with the start of the most prominent γ-ray outburst in 3C 454.3 (Abdo et al. 2011).”
• A hadronic origin for ultra-high-frequency-peaked BL Lac objects (2014, methodology): “Besides the small differences in the parameter values imposed by our physical constraints, our code fully reproduces the result presented in Abdo et al. (2011).”