论文标题
无线电源J1402+5347的极端时间内变异性用Apertif发现
Extreme intra-hour variability of the radio source J1402+5347 discovered with Apertif
论文作者
论文摘要
我们银河系中通过湍流的星际等离子体从遥远的紧凑型无线电来源传播的无线电波使这些来源闪烁，这是一种称为星际闪烁的现象。这样的闪烁是无线电源微弧形结构以及银河跨层介质的子AU规模结构的独特探针。通常在厘米波长时看到几天或更长时间的时间尺度上的弱闪烁（即，强度调节的强度调节），被认为是由于银河系星际等离子体中的视线构成湍流而导致的。到目前为止，只有三个来源显示出更大的差异，而调制的时间比一个小时短的时间尺度约为十二％。这需要通过附近（d <〜10 pc）的传播异常致密（N_E〜10^2 cm^-3）等离子体云。在这里，我们报告了源（J1402+5347）的APERTIF的发现，显示了极端（〜50％）和在Decimetre频段（1.4 GHz）中仅6.5分钟的时间表上的极端变化和快速变化。空间闪烁模式是高度各向异性的，半米轴约为20,000 km。折射闪烁的规范理论将散射等离子体限制为在Oort云中。然而，到J1402+5347的视线在32 pc的距离上与B3星烷烃（ETA UMA）的距离非常接近。如果闪烁与阿尔卡德相关，则沿闪烁的次要轴的J1402+5347的角度大小必须小于〜10 micro Arcsec，对于> 〜10^ 14K的各向同性源，产生明显的亮度温度。 }
The propagation of radio waves from distant compact radio sources through turbulent interstellar plasma in our Galaxy causes these sources to twinkle, a phenomenon called interstellar scintillation. Such scintillations are a unique probe of the micro-arcsecond structure of radio sources as well as of the sub-AU-scale structure of the Galactic interstellar medium. Weak scintillations (i.e. an intensity modulation of a few percent) on timescales of a few days or longer are commonly seen at centimetre wavelengths and are thought to result from the line-of-sight integrated turbulence in the interstellar plasma of the Milky Way. So far, only three sources were known that show more extreme variations, with modulations at the level of some dozen percent on timescales shorter than an hour. This requires propagation through nearby (d <~10 pc) anomalously dense (n_e ~10^2 cm^-3) plasma clouds. Here we report the discovery with Apertif of a source (J1402+5347) showing extreme (~50%) and rapid variations on a timescale of just 6.5 minutes in the decimetre band (1.4 GHz). The spatial scintillation pattern is highly anisotropic, with a semi-minor axis of about 20,000 km. The canonical theory of refractive scintillation constrains the scattering plasma to be within the Oort cloud. The sightline to J1402+5347, however, passes unusually close to the B3 star Alkaid (eta UMa) at a distance of 32 pc. If the scintillations are associated with Alkaid, then the angular size of J1402+5347 along the minor axis of the scintels must be smaller than ~10 micro arcsec yielding an apparent brightness temperature for an isotropic source of >~ 10^ 14K. }
