基于UVIT/AstroSat观测的耀变体紫外通量与光谱变化研究
Ultraviolet flux and spectral variability study of blazars observed with UVIT/AstroSat
AI总结：
本文利用AstroSat/UVIT对10个耀变体进行日内紫外监测，首次发现9个源存在小时级通量变化，并揭示其紫外辐射由喷流同步辐射主导。
摘要：
耀变体是活动星系核（AGN）中一类特殊的天体，已知在可观测的电磁波谱范围内表现出通量变化。尽管人们已对其跨波段的通量变化特征进行了广泛研究，但关于它们在小时时间尺度上的紫外（UV）通量变化信息仍然非常有限。本文首次对包含2个平谱射电类星体（FSRQs）和8个蝎虎天体（BL Lacs）在内的10个耀变体样本进行了日内时间尺度上的紫外通量变化研究。这些天体的红移（z）范围为0.034 ≤ z ≤ 1.003，利用AstroSat卫星上的紫外成像望远镜在远紫外（FUV：1300–1800 Å）和近紫外（NUV：2000–3000 Å）波段进行了观测。在观测的10个耀变体中，有9个源检测到了小时时间尺度上的紫外通量变化。光谱变化分析显示出越亮越蓝的趋势，且所研究的FSRQs与BL Lacs样本之间在紫外光谱变化行为上没有差异。我们在FSRQs和BL Lacs样本中观测到的紫外通量与光谱变化表明，它们观测到的紫外辐射主要由喷流同步辐射过程主导。
英文摘要：
Blazars, the peculiar class of active galactic nuclei (AGN), are known to show flux variations across the accessible electromagnetic spectrum. Though they have been studied extensively for their flux variability characteristics across wavelengths, information on their ultraviolet (UV) flux variations on time scales of hours is very limited. Here, we present the first UV flux variability study on intraday time scales of a sample of 10 blazars comprising 2 flat spectrum radio quasars (FSRQs) and 8 BL Lacertae objects (BL Lacs). These objects, spanning a redshift (z) range of 0.034 <= z <= 1.003, were observed in the far-UV (FUV: 1300 - 1800 \textÅ) and near-UV (NUV: 2000 - 3000 \textÅ) wavebands using the ultraviolet imaging telescope on board AstroSat. UV flux variations on time scales of hours were detected in 9 sources out of the observed 10 blazars. The spectral variability analysis showed a bluer-when-brighter trend with no difference in the UV spectral variability behavior between the studied sample of FSRQs and BL Lacs. The observed UV flux and spectral variability in our sample of both FSRQs and BL Lacs revealed that the observed UV emission in them is dominated by jet synchrotron process.
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