论文标题
中子恒星合并的基洛诺瓦早期排放的模拟
Simulations of early kilonova emission from neutron star mergers
论文作者
论文摘要
我们通过首次进行详细的不透明度计算，对中子星（NS）合并后的蓝色Kilonovae小时进行辐射转移模拟。我们用原子数z = 20-56计算高度离子化元件（直至第十个离子化）的原子结构和不透制。我们发现，重型元素的界限是早期阶段的主要偏差来源（在合并后的t <1天T <1天），并提供最高的电子壳的离子。 planck无灯笼弹射的平均不透明度（具有Ye = 0.30-0.40的电子分数）只能在t = 0.1天左右到达kappa〜0.5-1 cm^2 g^-1，而在t = 1天，最大增加到kappa〜5-5-10 cm^2 g^-1。具有MeJ = 0.05ms的射流质量的球形喷射模型在t〜0.1天时，辐射仪的光度为〜2 x 10^42 erg s^-1。我们确认GW170817的现有辐射法和多色数据可以通过纯放射性模型自然解释。即使在200 MPC时，源的预期早期紫外线信号在T〜4.3小时达到20.5 mag，这是由Swift和Ultraviolet瞬态天文学卫星（Ultrasat）等设施检测到的。正如Kasen等人所指出的那样，早期的光度对外喷射的结构很敏感。 （2017）。因此，早期的紫外线观察结果对外喷射的结构以及除R过程核以外的加热源的存在给出了强烈的限制。
We present radiative transfer simulations for blue kilonovae hours after neutron star (NS) mergers by performing detailed opacity calculations for the first time. We calculate atomic structures and opacities of highly ionized elements (up to the tenth ionization) with atomic number Z = 20 - 56. We find that the bound-bound transitions of heavy elements are the dominant source of the opacities in the early phase (t < 1 day after the merger), and that the ions with a half-closed electron shell provide the highest contributions. The Planck mean opacity for lanthanide-free ejecta (with electron fraction of Ye = 0.30 - 0.40) can only reach around kappa ~ 0.5 - 1 cm^2 g^-1 at t = 0.1 day, whereas that increases up to kappa ~ 5 - 10 cm^2 g^-1 at t = 1 day. The spherical ejecta model with an ejecta mass of Mej = 0.05Msun gives the bolometric luminosity of ~ 2 x 10^42 erg s^-1 at t ~ 0.1 day. We confirm that the existing bolometric and multi-color data of GW170817 can be naturally explained by the purely radioactive model. The expected early UV signals reach 20.5 mag at t ~ 4.3 hours for sources even at 200 Mpc, which is detectable by the facilities such as Swift and the Ultraviolet Transient Astronomy Satellite (ULTRASAT). The early-phase luminosity is sensitive to the structure of the outer ejecta, as also pointed out by Kasen et al. (2017). Therefore, the early UV observations give strong constraints on the structure of the outer ejecta as well as the presence of a heating source besides r-process nuclei.
