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arXiv 1403.0002astro-ph.HE
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超大质量黑洞双星的Lyman边

Lyman edges in supermassive black hole binaries

Aleksey Generozov, Zoltan Haiman

摘要:

我们提出了一个新的光谱特征的超大质量黑洞双星(SMBHB)的circumbinary气体盘:急剧下降的流量蓝莱曼极限。如果在光谱的莱曼连续区中占主导地位的气体足够冷(T <20,000 K)以包含大量的中性氢,则会产生突出的边缘。如果双星的扭矩在圆盘中打开一个中心空腔,并从内部区域清除大部分热气,并且如果来自单个BH的任何残余UV发射是暗淡的或间歇性的,则环双星圆盘可能处于这种状态。我们使用辐射转移代码TLUSTY模型的垂直结构和光谱的circumbinary磁盘,并确定BH质量和二元分离产生莱曼边缘的范围。我们发现,轨道周期为0.1 - 10年的紧凑超大质量双星,其引力波(GWs)预计将被脉冲星定时阵列(PTA)检测到,可能有突出的莱曼边缘。这样强的光谱边缘特征通常不存在于活动星系核的光谱中,可以作为SMBHB存在的佐证。

英文摘要:

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.

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