arXiv subjects

V. Baghmanyan

Publications and source records attributed to V. Baghmanyan.

39 records · Page 3Linked to original sources

arXiv2017

Comparing 3C 120 jet emission at small and large scales

Context. Important information on the evolution of the jet can be obtained by comparing the physical state of the plasma at its propagation through the broad-line region (where the jet is most likely formed) into the intergalactic medium, where it starts to significantly decelerate. Aims. We compare the constraints on the physical parameters in the innermost ($\leq$ pc) and outer ($\geq$ kpc) regions of the 3C 120 jet by means of a detailed multiwavelength analysis and theoretical modeling of their broadband spectra. Methods.The data collected by Fermi LAT, Swift and Chandra are analyzed together and the spectral energy distributions are modeled using a leptonic synchrotron and inverse Compton model, taking into account the seed photons originating inside and outside of the jet. The model parameters are estimated using the MCMC method. Results. The $γ$-ray flux from the inner jet of 3C 120 was characterized by rapid variation from MJD 56900 to MJD 57300. Two strong flares were observed on April 24, 2015 when, within 19.0 minutes and 3.15 hours the flux was as high as $(7.46\pm1.56)\times10^{-6}photon\:cm^{-2}\:s^{-1}$ and $(4.71\pm0.92)\times10^{-6}photon\:cm^{-2}\:s^{-1}$ respectively. The broadband emission in the quiet and flaring states can be described as SSC emission while IC scattering of dusty torus photons cannot be excluded for the flaring states. The X-ray emission from the knots can be well reproduced by IC scattering of CMB photons only if the jet is highly relativistic (since even when $δ=10$ still $U_{\rm e}/U_B\geq80$). These extreme requirements can be somewhat softened assuming the X-rays are from the synchrotron emission of a second population of very-high-energy electrons. Conclusions. We found that the jet power estimated at two scales is consistent, suggesting that the jet does not suffer severe dissipation, it simply becomes radiatively inefficient.

astro-ph.HE↗

arXiv2017

Rapid Gamma-ray variability of NGC 1275

We report on a detailed analysis of the $γ$-ray light curve of NGC 1275 using the Fermi large area telescope data accumulated in 2008-2017. Major $γ$-ray flares were observed in October 2015 and December 2016/January 2017 when the source reached a daily peak flux of $(2.21\pm0.26)\times10^{-6}\:{\rm photon\:cm^{-2}\:s^{-1}}$, achieving a flux of $(3.48\pm0.87)\times10^{-6}\:{\rm photon\:cm^{-2}\:s^{-1}}$ within 3 hours, which corresponds to an apparent isotropic $γ$-ray luminosity of $\simeq3.84\times10^{45}\:{\rm erg\:s^{-1}}$. The most rapid flare had e-folding time as short as $1.21\pm0.22$ hours which had never been previously observed for any radio galaxy in $γ$-ray band. Also $γ$-ray spectral changes were observed during these flares: in the flux versus photon index plane the spectral evolution follows correspondingly a counter clockwise and a clockwise loop inferred from the light curve generated by an adaptive binning method. On December 30, 2016 and January 01, 2017 the X-ray photon index softened ($Γ_{\rm X}\simeq 1.75-1.77$) and the flux increased nearly $\sim3$ times as compared with the quiet state. The observed hour-scale variability suggests a very compact emission region ($R_γ\leq5.22\times10^{14}\:(δ/4)\:{\rm cm}$) implying that the observed emission is most likely produced in the subparsec-scale jet if the entire jet width is responsible for the emission. During the active periods the $γ$-ray photon index hardened, shifting the peak of the high energy spectral component to $>{\rm GeV}$, making it difficult to explain the observed X-ray and $γ$-ray data in the standard one-zone synchrotron self-Compton model.

astro-ph.HE↗

arXiv2014

On the gamma-ray emission from 3C 120

We report the analysis of Fermi Large Area Telescope data from five years of observations of the broad line radio galaxy 3C 120. The accumulation of larger data set results in the detection of high-energy $γ$-rays up to 10 GeV, with a detection significance of about $8.7σ$. A power-law spectrum with a photon index of $2.72\pm0.1$ and integrated flux of $F_γ=(2.35\pm0.5)\times10^{-8}\:\mathrm{photon\:cm}^{-2}s^{-1}$ above 100 MeV well describe the data averaged over five year observations. The variability analysis of the light curve with 180-, and 365- day bins reveals flux increase (nearly twice from its average level) during the last year of observation. This variability on month timescales indicates the compactness of the emitting region. The $γ$-ray spectrum can be described as synchrotron self-Compton (SSC) emission from the electron population producing the radio-to-X-ray emission in the jet. The required electron energy density exceeds the one of magnetic field only by a factor of 2 meaning no significant deviation from equipartition.

astro-ph.HE↗