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arXiv 1102.5054astro-ph.HEastro-ph.GA
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微类星体XTE J1550-564中的近红外喷流发射

Near-infrared jet emission in the microquasar XTE J1550-564

Sylvain Chaty, Guillaume Dubus, Anand Raichoor

摘要:

背景:微类星体是银河系的吸积源,也被观察到发射相对论喷流。喷射的一个关键特征是非热无线电发射。在高频率下,这种射流分量的水平仍然受到很差的约束。目的:X射线双星和微类星体黑洞候选者XTE J1550-564在2003年4月表现出微弱的X射线爆发,在此期间它保持在X射线低/硬状态。我们采取了光学和近红外(NIR)观测与ESO/NTT望远镜在这次爆发解开的光谱能量分布(SED)的各种贡献,并调查存在的喷流组件。方法:光度和光谱观测使我们能够构建一个SED,并产生一个高时间分辨率的光变曲线。结果:从近红外域到光学域,SED显示斜率的突变。近红外发射归因于来自紧凑的自吸收射流的非热同步辐射,该自吸收射流已知存在于低/硬状态。这是由快速变化,颜色,缺乏突出的光谱特征和内在偏振的证据所证实的。SED表明近红外光谱中发生了从光学厚区到光学薄区的射流断裂。结论:同时光学近红外数据允许一个独立的确认喷射发射的近红外。在近红外频率或更低的频率下,发生向光学薄同步加速器的转变,这导致估计的特征尺寸大于2 × 10^8 cm,并且假设均匀的单区同步加速器模型,喷流基底的磁场小于5 T。

英文摘要:

Context: Microquasars are accreting Galactic sources that are also observed to launch relativistic jets. A key signature of the ejection is non-thermal radio emission. The level of this jet component at high frequencies is still poorly constrained. Aims: The X-ray binary and microquasar black hole candidate XTE J1550-564 exhibited a faint X-ray outburst in April 2003 during which it stayed in the X-ray low/hard state. We took optical and near-infrared (NIR) observations with the ESO/NTT telescope during this outburst to disentangle the various contributions to the spectral energy distribution (SED) and investigate the presence of a jet component. Methods: Photometric and spectroscopic observations allowed us to construct an SED and also to produce a high time-resolution lightcurve. Results: The SED shows an abrupt change of slope from the NIR domain to the optical. The NIR emission is attributed to non-thermal synchrotron emission from the compact, self-absorbed jet that is known to be present in the low/hard state. This is corroborated by the fast variability, colours, lack of prominent spectral features and evidence for intrinsic polarisation. The SED suggests the jet break from the optically thick to the thin regime occurs in the NIR. Conclusions: The simultaneous optical-NIR data allow an independent confirmation of jet emission in the NIR. The transition to optically thin synchrotron occurs at NIR frequencies or below, which leads to an estimated characteristic size greater than 2x10^8cm and magnetic field less than 5T for the jet base, assuming a homogeneous one-zone synchrotron model.

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