论文标题
在二进制中子星的视角上的余花约束和哈勃常数的确定
Afterglow constraints on the viewing angle of binary neutron star mergers and determination of the Hubble constant
论文作者
论文摘要
任何二进制的关键属性之一是其视角（即倾斜度），$θ_ {\ rm obs} $。在二进制中子星（BNS）合并中，由于它在测量哈勃常数（$ h_0 $）中所扮演的作用，因此非常重要。这些合并推出的$θ_J$的喷气机的开头也引起了特别的兴趣。在发现第一BNS合并GW170817之后，有许多尝试使用余波光曲线估算这些角度的尝试，发现了广泛的值。在这里，我们根据余波光曲线为比率$θ_{\ rm obs}/θ_j$提供一个简单的公式，并证明这是仅从光曲线确定的唯一数量。也就是说，没有其他信息，就不可能分别确定每个角度。我们的结果解释了GW170817的各种研究所发现的值的不一致性，这些研究主要由每项研究中所采用的不同先验驱动。在可用于估计$θ_ {\ rm obs} $和$θ_j$的其他信息中，最有用的是对余辉图像超亮性运动的VLBI测量。一种替代方法是鉴定余辉过渡到亚偏见阶段。这些观察仅对于在小视角上观察到的合并才能进行，其余辉明显比检测器的阈值明显明亮。我们讨论了这些结果对使用GW观测值$ H_0 $的测量的含义。我们表明，虽然观看角仅在未来BNS合并的一小部分中进行测量，但它可以大大降低这些事件中每一个中$ H_0 $的不确定性，可能会降低到4-5 \％的水平。这种类型的高精度测量值的少数合并可能会在将来占主导地位。在将来使用此方法测量$ H_0 $的精度。
One of the key properties of any binary is its viewing angle (i.e., inclination), $θ_{\rm obs}$. In binary neutron star (BNS) mergers it is of special importance due to the role that it plays in the measurement of the Hubble constant, $H_0$. The opening angle of the jet that these mergers launch, $θ_j$, is also of special interest. Following the detection of the first BNS merger, GW170817, there were numerous attempts to estimate these angles using the afterglow light curve, finding a wide range of values. Here we provide a simple formula for the ratio $θ_{\rm obs}/θ_j$ based on the afterglow light curve and show that this is the only quantity that can be determined from the light curve alone. Namely, it is impossible to determine each of the angles separately without additional information. Our result explains the inconsistency of the values found by the various studies of GW170817 that were largely driven by the different priors taken in each study. Among the additional information that can be used to estimate $θ_{\rm obs}$ and $θ_j$, the most useful is a VLBI measurement of the afterglow image superluminal motion. An alternative is an identification of the afterglow transition to the sub-relativistic phase. These observations are possible only for mergers observed at small viewing angles, whose afterglow is significantly brighter than the detector's threshold. We discuss the implications of these results to measurements of $H_0$ using GW observations. We show that while the viewing angle will be measured only in a small fraction of future BNS mergers, it can significantly reduce the uncertainty in $H_0$ in each one of these events, possibly to a level of 4-5\%. A minority of the mergers with high precision measurements of this kind may dominate in the future the precision in which $H_0$ will be measured using this method.
