标题： 同步辐射自吸收在伽马射线暴余辉中的应用 显示英文标题

标题： Synchrotron Self Absorption in GRB Afterglow

摘要： 伽马射线暴余辉在宇宙距离上可以通过相对论爆轰波的同步辐射发射合理描述。 我们进行了详细的计算，考虑了同步辐射自吸收的影响。 我们考虑冲击波前缘之后整个区域的发射，并使用Blandford McKee自相似解来描述冲击波后的流体。 我们在自吸收频率$\nu_a$附近计算了伽马射线暴余辉的光谱和观测图像，并推导出对$\nu_a$的精确表达式。 我们表明，对于$\nu<\nu_a$，图像相当均匀，与在较高频率下出现的外缘明亮环和中心昏暗的情况相反。 我们将自吸收频率附近的光谱计算与其他部分的光谱相结合，得到了爆发的物理参数的修正估计：$E_{52}=0.53$，$\epsilon_e=0.57$，$\epsilon_B=0.0082$，$n_1=5.3$。 这些估计与基于近似光谱的估计相差多达两个数量级。 显示英文摘要

摘要： GRB afterglow is reasonably described by synchrotron emission from relativistic blast waves at cosmological distances. We perform detailed calculations taking into account the effect of synchrotron self absorption. We consider emission from the whole region behind the shock front, and use the Blandford McKee self similar solution to describe the fluid behind the shock. We calculate the spectra and the observed image of a GRB afterglow near the self absorption frequency $\nu_a$ and derive an accurate expression for $\nu_a$. We show that the image is rather homogeneous for $\nu<\nu_a$, as opposed to the bright ring at the outer edge and dim center, which appear at higher frequencies. We compare the spectra we obtain to radio observations of GRB970508. We combine the calculations of the spectra near the self absorption frequency with other parts of the spectra and obtain revised estimates for the physical parameters of the burst: $E_{52}=0.53$, $\epsilon_e=0.57$, $\epsilon_B=0.0082$, $n_1=5.3$. These estimates are different by up to two orders of magnitude than the estimates based on an approximate spectrum.