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arXiv 0902.4708astro-ph.HE
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快辐射介导的激波和超新星激波爆发

Fast radiation mediated shocks and supernova shock breakouts

Boaz Katz, Ran Budnik, Eli Waxman

摘要:

我们提出了一个简单的非相对论和相对论辐射介导的冲击结构的分析模型。当激波速度β_s \equiv v_s/c \gtrsim 0.1时,激波转捩区远离热平衡,因为转捩的穿越时间太短,不能产生黑体光子密度(通过韧致辐射)。在这个区域中,电子和光子(以及正电子)在温度T_s显著超过远下游温度T_s \gg T_d \approx 2(\varepsilon n_u \hbar^3 c^3)^{1/4}时处于康普顿(对)平衡。当冲击波速度β_s \approx为0.2时,T_s \gtrsim达到10 keV。在较高的速度下,β_s \gtrsim = 0.6,在过渡区等离子体主要是e^ \pm对和60 keV的\lesssim T_s \lesssim 200 keV。我们认为,在蓝超巨星和沃尔夫-拉叶星的恒星包层(或周围的恒星风)爆发超新星激波时,在合理的恒星参数下β_s>0.1的谱线中,可能含有光子能量达几十甚至几百keV的硬谱线。这可能解释了与SN 2008 D相关的X射线爆发,也可能解释了其他与SN相关的爆发,其光谱不超过100 keV(例如XRF 060218/SN 2006 aj)。

英文摘要:

We present a simple analytic model for the structure of non-relativistic and relativistic radiation mediated shocks. At shock velocities β_s\equiv v_s/c\gtrsim 0.1, the shock transition region is far from thermal equilibrium, since the transition crossing time is too short for the production of a black-body photon density (by Bremsstrahlung emission). In this region, electrons and photons (and positrons) are in Compton (pair) equilibrium at temperatures T_s significantly exceeding the far downstream temperature, T_s\gg T_d\approx 2(\varepsilon n_u \hbar^3c^3)^{1/4}. T_s\gtrsim 10 keV is reached at shock velocities β_s\approx 0.2. At higher velocities, β_s\gtrsim0.6, the plasma is dominated in the transition region by e^\pm pairs and 60 keV\lesssim T_s \lesssim 200 keV. We argue that the spectrum emitted during the breaking out of supernova shocks from the stellar envelopes (or the surrounding winds) of Blue Super Giants and Wolf-Rayet stars, which reach β_s>0.1 for reasonable stellar parameters, may include a hard component with photon energies reaching tens or even hundreds of keV. This may account for the X-ray outburst associated with SN2008D, and possibly for other SN-associated outbursts with spectra not extending beyond few 100 keV (e.g. XRF060218/SN2006aj).

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