Shock-powered radio emission from V5589 Sagittarii (Nova Sgr 2012 #1)
Shock-powered radio emission from V5589 Sagittarii (Nova Sgr 2012 #1)
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V5589 Sagittarii (Nova Sgr 2012) 的冲击动力无线电发射
DOI：
10.1093/mnras/stw1161
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发表时间：
2015
影响因子：
4.8
通讯作者：
F. Walter
中科院分区：
文献类型：
--
作者：
J. Weston;J. Sokoloski;L. Chomiuk;J. Linford;T. Nelson;K. Mukai;T. Finzell;A. Mioduszewski;M. Rupen;F. Walter
自从费米发现了来自新星的$\gamma$-射线以来，该领域最大的问题之一就是新星如何产生如此高能量的辐射。冲击必须是一个基本要素。VLA对2012年新星V5589 Sgr进行了6个月的射电观测，Swift/XRT进行了15周的X射线观测，结果表明射电辐射包括：1）一个冲击动力的非热耀斑; 2）来自10 ^{-5}$ M$\odot$自由膨胀的光电离喷出物的微弱热辐射。光谱中的吸收特征和峰值光学亮度表明V5589 Sgr位于4 kpc（3.2-4.6 kpc）之外。在第100天之前，激波驱动的耀斑在低频率下占据了射电光变曲线的主导地位。射电耀斑的光谱演化、高射电亮温度、异常硬（$kT_x > 33$ keV）X射线的存在以及射电与X射线通量的比值接近射电极大值，都支持耀斑是激波驱动的非热耀斑的结论。与大多数其他具有强烈冲击动力无线电发射的新星不同，V5589 Sgr没有嵌入红巨星伴星的风中。基于V5589 Sgr和V959 Mon相似的倾角和光学线轮廓，我们认为V5589 Sgr中的激波是由具有赤道密度增强的慢流与随后的较快流之间的碰撞形成的。我们推测，相对较高的速度和低质量的喷出物导致了V5589 Sgr的不寻常的无线电发射，也许也没有检测到$\gamma$-射线。
Since the Fermi discovery of $\gamma$-rays from novae, one of the biggest questions in the field has been how novae generate such high-energy emission. Shocks must be a fundamental ingredient. Six months of radio observations of the 2012 nova V5589 Sgr with the VLA and 15 weeks of X-ray observations with Swift/XRT show that the radio emission consisted of: 1) a shock-powered, non-thermal flare; and 2) weak thermal emission from $10^{-5}$ M$_\odot$ of freely expanding, photoionized ejecta. Absorption features in the optical spectrum and the peak optical brightness suggest that V5589 Sgr lies 4 kpc away (3.2-4.6 kpc). The shock-powered flare dominated the radio light curve at low frequencies before day 100. The spectral evolution of the radio flare, its high radio brightness temperature, the presence of unusually hard ($kT_x > 33$ keV) X-rays, and the ratio of radio to X-ray flux near radio maximum all support the conclusions that the flare was shock-powered and non-thermal. Unlike most other novae with strong shock-powered radio emission, V5589 Sgr is not embedded in the wind of a red-giant companion. Based on the similar inclinations and optical line profiles of V5589 Sgr and V959 Mon, we propose that shocks in V5589 Sgr formed from collisions between a slow flow with an equatorial density enhancement and a subsequent faster flow. We speculate that the relatively high speed and low mass of the ejecta led to the unusual radio emission from V5589 Sgr, and perhaps also to the non-detection of $\gamma$-rays.
复发新星天蝎座 U 2010 年爆发和爆发前的光谱
影响因子：
6.5
作者：
Anupama G
通讯作者：
Anupama G