Title: Lyman edges in supermassive black hole binaries Show Chinese title

Title: 超大质量黑洞双星的莱曼边缘

Abstract: We propose a new spectral signature for supermassive black hole binaries (SMBHBs) with circumbinary gas disks: a sharp drop in flux blueward of the Lyman limit. A prominent edge is produced if the gas dominating the emission in the Lyman continuum region of the spectrum is sufficiently cold (T < 20,000 K) to contain significant neutral hydrogen. Circumbinary disks may be in this regime if the binary torques open a central cavity in the disk and clear most of the hot gas from the inner region, and if any residual UV emission from the individual BHs is either dim or intermittent. We model the vertical structure and spectra of circumbinary disks using the radiative transfer code TLUSTY, and identify the range of BH masses and binary separations producing a Lyman edge. We find that compact supermassive binaries with orbital periods of ~0.1 - 10 yr, whose gravitational waves (GWs) are expected to be detectable by pulsar timing arrays (PTAs), could have prominent Lyman edges. Such strong spectral edge features are not typically present in AGN spectra and could serve as corroborating evidence for the presence of a SMBHB. Show Chinese abstract

Abstract: 我们提出了一种新的超大质量黑洞双星（SMBHBs）及其周围气体盘的光谱特征：在莱曼极限蓝端出现急剧的流量下降。 如果主导莱曼连续区谱线发射的气体足够冷（T < 20,000 K），包含显著的中性氢，则会产生一个明显的边缘。 如果双星的潮汐力在盘中打开一个中央空腔，并清除内区大部分热气体，且来自单个黑洞的剩余紫外辐射较弱或间歇性，则周围的气体盘可能处于这种状态。 我们使用辐射转移代码TLUSTY模拟了周围气体盘的垂直结构和光谱，并确定了产生莱曼边缘的黑洞质量和双星分离范围。 我们发现，轨道周期约为0.1至10年的紧凑型超大质量双星，其引力波（GWs）预计可以通过脉冲星定时阵列（PTAs）探测到，可能具有显著的莱曼边缘。 这种强烈的光谱边缘特征通常不在活动星系核（AGN）光谱中存在，可作为超大质量双黑洞存在的佐证证据。