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arXiv 2102.13449astro-ph.HE
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Hoinga:在SRG/eROSITA全天巡天eRASS1中发现的超新星遗迹

Hoinga: A supernova remnant discovered in the SRG/eROSITA All-Sky Survey eRASS1

W. Becker, N. Hurley-Walker, Ch. Weinberger, L. Nicastro, M. G. F. Mayer, A. Merloni, J. Sanders

摘要:

超新星遗迹(SNRs)在消失在银河系星际介质之前,可以观测到大约6-15x10^4年。银河系超新星的发生率大约为每世纪两颗,我们可以预期银河系中有1200颗超新星。然而,迄今为止只有大约300个已知的,其中大多数是在银河平面无线电调查中发现的。考虑到这些SNR代表分布的最亮尾部,并且大多位于平面附近,它们不能代表完整的样本。在这里,我们报告了在eROSITA全天空调查数据中搜索新SNR的结果,这些数据导致检测到在无线电以外的波长发现的最大SNR之一:G249.5+24.5。这个辐射源位于银河系相对较高的纬度,在那里通常不会发现信噪比。残骸“Hoinga”直径约为4.4度,呈圆形形态,几乎整个残骸都充满了弥漫的X射线辐射。对残余辐射的光谱分析表明,来自碰撞电离扩散气体的APEC光谱和具有非平衡电离的平面平行激波等离子体模型都能够提供对数据的充分描述,表明气体温度为kT = 0.1 keV,吸收柱密度为N_H=3.6 x 10^20 cm^-2。随后对Hoinga残骸的无线电对应物的搜索在Continuum HI Parkes全天巡天(CHIPASS)和408-MHz 'Haslam'全天巡天的档案数据中确定了它的无线电发射。从这些数据中得到的射电频谱指数α =-0.69 +-0.08肯定地证实了Hoinga的信噪比性质。从它的大小和X射线和射电光谱特性,我们得出结论,Hoinga是一个中年Vela类SNR,位于大约两倍的Vela SNR的距离,即在~500 pc。

英文摘要:

Supernova remnants (SNRs) are observable for about 6-15x10^4 years before they fade into the Galactic interstellar medium. With a Galactic supernova rate of approximately two per century, we can expect to have of the order of 1200 SNRs in our Galaxy. However, only about 300 of them are known to date, with the majority having been discovered in Galactic plane radio surveys. Given that these SNRs represent the brightest tail of the distribution and are mostly located close to the plane, they are not representative of the complete sample. Here we report findings from the search for new SNRs in the eROSITA all-sky survey data which led to the detection of one of the largest SNRs discovered at wavelengths other than the radio: G249.5+24.5. This source is located at a relatively high Galactic latitude, where SNRs are not usually expected to be found. The remnant, 'Hoinga', has a diameter of about 4.4 degrees and shows a circular shaped morphology with diffuse X-ray emission filling almost the entire remnant. Spectral analysis of the remnant emission reveals that an APEC spectrum from collisionally ionised diffuse gas and a plane-parallel shock plasma model with non-equilibrium ionisation are both able to provide an adequate description of the data, suggesting a gas temperature of the order of kT = 0.1 keV and an absorbing column density of N_H=3.6 x 10^20 cm^-2. Subsequent searches for a radio counterpart of the Hoinga remnant identified its radio emission in archival data from the Continuum HI Parkes All-Sky Survey (CHIPASS) and the 408-MHz `Haslam' all-sky survey. The radio spectral index alpha=-0.69 +- 0.08 obtained from these data definitely confirms the SNR nature of Hoinga. From its size and X-ray and radio spectral properties we conclude that Hoinga is a middle-aged Vela-like SNR located at a distance of about twice that of the Vela SNR, i.e. at ~500 pc.

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