Please use this identifier to cite or link to this item: http://hdl.handle.net/2445/120043
Title: A Search for Spectral Hysteresis and Energy-dependent Time Lags from X-Ray and TeV Gamma-Ray Observations of Mrk 421
Author: Galindo, D.
Marcote Martin, Benito
Paredes i Poy, Josep Maria
Paredes Fortuny, Xavier
Ribó Gomis, Marc
Torres-Albà, N.
Zanin, Roberta
MAGIC Collaboration
VERITAS Collaboration
Keywords: Galàxies
Raigs gamma
Galaxies
Gamma rays
Issue Date: 1-Jan-2017
Publisher: Institute of Physics (IOP)
Abstract: 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 gsim4 × 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.
Note: Reproducció del document publicat a: https://doi.org/10.3847/1538-4357/834/1/2
It is part of: Astrophysical Journal, 2017, vol. 834, num. 2
URI: http://hdl.handle.net/2445/120043
Related resource: https://doi.org/10.3847/1538-4357/834/1/2
ISSN: 0004-637X
Appears in Collections:Articles publicats en revistes (Institut de Ciències del Cosmos (ICCUB))
Articles publicats en revistes (Física Quàntica i Astrofísica)

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