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Bibliographical reference
The Astrophysical Journal, Volume 834, Issue 1, article id. 2, 18 pp. (2017).
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2017
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Citations
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Refereed citations
28
Description
Blazars are variable emitters across all wavelengths over a wide range
of timescales, from months down to minutes. It is therefore essential to
observe blazars simultaneously at different wavelengths, especially in
the X-ray and gamma-ray bands, where the broadband spectral energy
distributions usually peak. In this work, we report on three
“target-of-opportunity” observations of Mrk 421, one of the
brightest TeV blazars, triggered by a strong flaring event at TeV
energies in 2014. These observations feature long, continuous, and
simultaneous exposures with XMM-Newton (covering the X-ray and
optical/ultraviolet bands) and VERITAS (covering the TeV gamma-ray
band), along with contemporaneous observations from other gamma-ray
facilities (MAGIC and Fermi-Large Area Telescope) and a number of radio
and optical facilities. Although neither rapid flares nor significant
X-ray/TeV correlation are detected, these observations reveal subtle
changes in the X-ray spectrum of the source over the course of a few
days. We search the simultaneous X-ray and TeV data for spectral
hysteresis patterns and time delays, which could provide insight into
the emission mechanisms and the source properties (e.g., the radius of
the emitting region, the strength of the magnetic field, and related
timescales). The observed broadband spectra are consistent with a
one-zone synchrotron self-Compton model. We find that the power spectral
density distribution at ≳4 × 10-4 Hz from
the X-ray data can be described by a power-law model with an index value
between 1.2 and 1.8, and do not find evidence for a steepening of the
power spectral index (often associated with a characteristic length
scale) compared to the previously reported values at lower frequencies.
Related projects
Particle Astrophysics
The MAGIC Collaboration is integrated by 20 research institutes and university departments from Armenia, Bulgaria, Finland, Germany, Italy, Poland, Spain, Switzerland and USA. The collaboration comprises two 17m diameter telescopes, located at the Roque de los Muchachos Observatory, designed to measure the Cherenkov radiation associated with
Ramón
García López