利用AstroSat观测解译J0710 +591异常弯曲的X射线谱
Unravelling the unusually curved X-ray spectrum of RGB J0710+591 using AstroSat observations
摘要：
我们报告的高能量峰值blazar RGB J 0710 +591的同时多波长数据的分析从LAXPC，SXT和UVIT仪器上的AstroSat。宽带X射线光谱（0.35 - 30 keV）被建模为从非热分布的高能电子的同步辐射。光谱是不寻常的弯曲，与曲率参数$β_p \sim 6.4$的对数抛物线粒子分布，或高能量谱指数$p_2 > 4.5$的打破幂律分布。光谱显示比早期Swift-XRT/NuSTAR数据的准同时分析更弯曲，其中参数为$β_p \sim 2.2$或$p_2 \sim 4$。在费米过程中，粒子被加速的区域可以产生幂律分布的电子，加速区的辐射损失决定了最大的洛伦兹因子$γ_{max}$。因此，这个量决定了光谱急剧弯曲的能量。我们发现，这样的分布提供了一个更自然的解释AstroSat的数据，以及较早的XRT/NuSTAR观测，使这作为第一个很好的约束确定对应于$γ_{max}$的光子能量。这又提供了作为磁场和多普勒因子的函数的加速度时间尺度的估计。UVIT观测结果与早期的光学/紫外线测量结果一致，并再次确认它们可能对应于不同于X射线发射的辐射成分。
英文摘要：
We report the analysis of simultaneous multi-wavelength data of the high energy peaked blazar RGB J0710+591 from the LAXPC, SXT and UVIT instruments on-board AstroSat. The wide band X-ray spectrum (0.35 -- 30 keV) is modelled as synchrotron emission from a non-thermal distribution of high energy electrons. The spectrum is unusually curved, with a curvature parameter $β_p \sim 6.4$ for a log parabola particle distribution, or a high energy spectral index $p_2 > 4.5$ for a broken power-law distribution. The spectrum shows more curvature than an earlier quasi-simultaneous analysis of Swift-XRT/NuSTAR data where the parameters were $β_p \sim 2.2$ or $p_2 \sim 4$. It has long been known that a power-law electron distribution can be produced from a region where particles are accelerated under Fermi process and the radiative losses in acceleration site decide the maximum attainable Lorentz factor, $γ_{max}$. Consequently, this quantity decides the energy at which the spectrum curves steeply. We show that such a distribution provides a more natural explanation for the AstroSat data as well as the earlier XRT/NuSTAR observation, making this as the first well constrained determination of the photon energy corresponding to $γ_{max}$. This in turn provides an estimate of the acceleration time-scale as a function of magnetic field and Doppler factor. The UVIT observations are consistent with earlier optical/UV measurements and reconfirm that they plausibly correspond to a different radiative component than the one responsible for the X-ray emission.
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