Accreting supermassive binary black holes (SMBBHs) are potential targets for multi-messenger astronomy as they emit gravitational waves (GW) while their environment emits electromagnetic (EM) waves. In order to get the most out of a joint GW-EM detection we first need to obtain theoretically-predicted EM signals unambiguously linked to BBHs. In that respect, this is the first of a series of papers dedicated to accreting pre-merger BBHs and their associated EM observables. Here, we extend our Numerical Observatory of Violent Accreting systems, e-NOVAs, to any spacetime. Unlike previous studies, almost exclusively focused on the inner regions, we investigated the impact of the BBH on its outer circumbinary disc, located in the radiation (or wave) zone, after implementing an approximate analytical spacetime of spinning, inspiralling BBHs in e-NOVAs. We follow the formation of a weak spiral structure in disc density arising from the retardation effects in the radiation zone metric. Simulation data are then post-processed with a general-relativistic ray-tracing code incorporating the same BBH spacetime, assuming SMBBH sources. The density spiral creates a small (<1%) but unambiguous modulation of the lightcurve at the semi-orbital period. This signal, although weak, is fundamentally different from that of an axisymmetric disc around a single BH providing a lower limit on the impact of a BBH on its outer disc. This potential difference being found, we study how binary parameters impact this modulation in order to find the optimal case which is a high source inclination of any binary mass ratio (from 0.1 to 1).
Relativistic Effects on Circumbinary Orbit Stability
Instituto de Astrofísica de La Plata, CCT La Plata-CONICET-UNLP（拉普拉塔天体物理研究所）；Facultad de Ciencias Astronómicas y Geofísicas de La Plata, UNLP（拉普拉塔大学天文与地球物理学院）；Nevada Center for Astrophysics, University of Nevada, Las Vegas（内华达大学拉斯维加斯分校天体物理中心）；Department of Physics and Astronomy, University of Nevada, Las Vegas（内华达大学拉斯维加斯分校物理与天文学系）
一般来说，当气体吸积到一个超大质量黑洞双星上时，它很可能没有双星角动量的先验知识。因此，环双星盘相对于双星有一个随机的倾角θ。已知对于θ < 90 degrees the disc will coalign wrt the binary. If theta >90度，如果满足cos（θ）< -J_d/2J_b，则盘完全反向对准，其中J_d和J_b分别是盘和二进制角动量矢量的大小。然而，如果θ> 90度并且不满足该标准，则相同的盘可以使其内部区域反向对准，并且在更长的时间尺度上，使其外部区域共对准。我表明，对于典型的光盘参数，描述吸积事件的超大质量黑洞二进制，未对准的circumbinary光盘可能是完全合作-或反-对齐的二进制平面。这是因为双星的角动量占主导地位的光盘角动量。然而，对于极端参数（二进制质量比M_2/M_1 << 1或二进制偏心率e ~ 1），同一盘可以同时共对准和反向对准。已知共面双旋双星盘是稳定的。我表明，共面逆行环双星盘也是稳定的。因此，一个混沌吸积事件在SMBH联星上将导致一个共面的环联星盘，它相对于联星平面是反的或反的。
$\textit{BMAD}$-Circumbinary Magnetically Arrested Disks around Stellar or Black Hole Binaries: Hot Accretion Flows, Disk Properties, and Angular Momentum Transfer
