High Energy Gamma-Ray Emission From PKS 1441+25

Abstract

We present the $\gamma$-ray observations of the flat-spectrum radio quasar PKS 1441+25 (z=0.939), using the {\it Fermi} large Area Telescope data accumulated during January - December 2015. A $\gamma$-ray flare was observed in January 24, when the flux increased up to $(2.22\pm 0.38)\times 10^{-6}\mathrm{photon}\mathrm{c}{\mathrm{m}}^{-2}{\mathrm{s}}^{-1}$ with the flux-doubling time scale being as short as $\sim 1.44$ days. The spectral analysis shows that from April 13 to April 28, 2015 the MeV-to-GeV photon index has hardened and changes in the range of $\Gamma =(1.73-1.79)$ for most of the time. The hardest photon index of $\Gamma =1.54\pm 0.16$ has been observed on MJD 57131.46 with $11.8\sigma$ which is not common for flat-spectrum radio quasars. For the same period the \gray spectrum shows a possible deviation from a simple power-law shape, indicating a spectral cutoff at $E_{\mathrm{cut}}=17.7\pm 8.9$ GeV. The spectral energy distributions during quiescent and flaring states are modeled using one-zone leptonic models that include the synchrotron, synchrotron self Compton and external inverse Compton processes; the model parameters are estimated using the Markov Chain Monte Carlo method. The emission in the flaring states can be modeled assuming that either the bulk Lorentz factor or the magnetic field has increased. The modeling shows that there is a hint of hardening of the low-energy index ($\sim 1.98$) of the underlying non-thermal distribution of electrons responsible for the emission in April 2015. Such hardening agrees with the $\gamma$-ray data, which pointed out a significant $\gamma$-ray photon index hardening on April 13 to 28, 2015.

Accepted for publication in MNRAS

References in corpus (8)

• The power of blazar jets
• The power of relativistic jets is larger than the luminosity of their accretion disks
• Synchrotron Self-Compton Analysis of TeV X-ray Selected BL Lacertae Objects
• GeV breaks in blazars as a result of gamma-ray absorption within the broad-line region
• Black hole lightning due to particle acceleration at subhorizon scales
• Fermi/LAT broad emission line blazars
• Intrinsic $\gamma$-ray luminosity, black hole mass, jet and accretion in Fermi blazars
• Radio-Gamma-ray connection and spectral evolution in 4C +49.22 (S4 1150+49): the Fermi, Swift and Planck view

Cited by in corpus (8)

• Multiwavelength Study of High-Redshift Blazars
• The Origin of the Multiwavelength Emission of PKS 0502+049
• Modeling the Broadband Emission of 3C 454.3
• Broadband Study of High-Synchrotron-Peaked BL Lac Object 1ES 1218+304
• Modeling the time variable spectral energy distribution of the blazar CTA 102 from 2008 to 2022
• Investigation of the Gamma-ray Spectrum of CTA 102 During the Exceptional Flaring State in 2016-2017
• Origin of multiwavelength emission from flaring high redshift blazar PKS 0537-286
• A precessing jet from a supermassive black hole: multi-wavelength observations of S5 1044+71