2015-16年期间HBL 1 ES 1959+650耀斑活动的多波长研究
Multi-wavelength study of flaring activity in HBL 1ES 1959+650 during 2015-16
摘要：
我们介绍了2015年1月至2016年6月期间对HBL 1 ES 1959+650的耀斑活动进行多波长研究的结果。该源经历了显着的通量增强，显示出光学，紫外线，X射线和伽马射线的两次主要爆发（2015年3月和2015年10月）。通常情况下，HBL不是很活跃，但1 ES 1959+650在整个电磁波谱（EMS）中显示出异常的爆发活动。我们使用了Fermi-LAT，Swift-XRT和UVOT的数据和Mt. Abu Reid天文台（MIRO）的数据以及Steward天文台的档案数据，以寻找不同能量的排放与耀斑状态期间可变性性质之间的可能联系。在2015年10月爆发期间，13个夜晚的光学跟踪观测显示，最亮和最暗的夜间平均V波段震级分别为14.45（0.03）和14.85（0.02）。在光学上，该源在爆发期间显示出光学夜间变化的暗示。还注意到MJD 57344至MJD 57365期间的光学和MJD 57360和MJD 57365期间的伽马射线存在显著的短期变化。多波长研究表明，耀斑活动在所有频率的相关性一般，虽然不同的耀斑持续时间。我们估计的磁场的强度为4.21 G使用的同步辐射冷却时间尺度（2.34小时）之间的光学和紫外波段的时间滞后。使用最短的变化时间尺度，伽马射线和光学发射区的大小上限估计为10^16 cm量级。在15 GHz和VHE伽马射线发射的准同步通量增强表明，新鲜的等离子体注入到射流中，它与一个站立的亚毫米核心相互作用，导致跨EMS的共空间发射。详细讨论了2015年10月第二次突出的复杂和长期行为。
英文摘要：
We present the results from a multiwavelength study of the flaring activity in HBL, 1ES 1959+650, during January 2015-June 2016. The source underwent significant flux enhancements showing two major outbursts (March 2015 and October 2015) in optical, UV, X-rays and gamma-rays. Normally, HBLs are not very active but 1ES 1959+650 has shown exceptional outburst activity across the whole electromagnetic spectrum (EMS). We used the data from Fermi-LAT, Swift-XRT & UVOT and optical data from Mt. Abu InfraRed Observatory (MIRO) along with archival data from Steward Observatory to look for possible connections between emissions at different energies and the nature of variability during flaring state. During October 2015 outburst, thirteen nights of optical follow-up observations showed brightest and the faintest nightly averaged V-band magnitudes as 14.45(0.03) and 14.85(0.02), respectively. In optical, the source showed a hint of optical intra-night variability during the outburst. A significant short-term variability in optical during MJD 57344 to MJD 57365 and in gamma-rays during MJD 57360 and MJD 57365 was also noticed. Multiwavelength study suggests the flaring activity at all frequencies to be correlated in general, albeit with diverse flare durations. We estimated the strength of the magnetic field as 4.21 G using the time-lag between optical and UV bands as synchrotron cooling time scale (2.34 hrs). The upper limits on the sizes of both the emission regions, gamma-ray and optical, are estimated to be of the order of 10^16cm using shortest variability time scales. The quasi-simultaneous flux enhancements in 15 GHz and VHE gamma-ray emissions indicates to a fresh injection of plasma into the jet, which interacts with a standing sub-mm core resulting in co-spatial emissions across the EMS. The complex and prolonged behavior of the second outburst in October 2015 is discussed in detail.
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