X-ray Flux and Spectral Variability of Six TeV Blazars with \textit{NuSTAR}

Abstract

We report the first results of timing and spectral studies of \textit{Nuclear Spectroscopic Telescope Array (NuSTAR)} observations of six TeV emitting high-frequency peaked blazars: 1ES 0347$-$121, 1ES 0414$+$009, RGB J0710$+$591, 1ES 1101$-$232, 1ES 1218$+$304 and H 2356-309. Two out of these six TeV blazars, 1ES 1101$-$232 and 1ES 1218$+$304, showed strong evidence of intraday variations in the 3--79 keV energy range during those observations. We also found a hint of an intraday variability timescale of 23.5 ks in the light curve of 1ES 1218$+$304 using an autocorrelation function analysis. We obtained magnetic field $B\sim 0.03$ G, electron Lorentz factor $\gamma \sim 2.16\times 10^6$ and emission region size $R\sim 1.19\times 10^{16}$ cm for 1ES 1218$+$304 using that variability timescale. The other blazars' light curves do not show any variability timescales shorter than their observation lengths; however, we note that the data were both noisier and sparser for them. We also investigated the spectral shape of these TeV blazars and found that the spectrum of 1ES 0414$+$009 is well described by a single power-law with photon index $\Gamma \sim 2.77$. The spectra of the other five HBLs are somewhat better represented by log-parabola models with local photon indices (at 10 keV) $\alpha \sim 2.23-2.67$ and curvature parameters, $\beta \sim 0.27-0.43$.

12 pages, 4 figures, accepted for publication in Astrophysical Journal (ApJ)

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• X-ray spectral studies of TeV gamma-ray emitting blazars
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