arXivDaily arXiv每日学术速递 周一至周五更新
arXiv周末暂无论文更新,休息一下吧,周末愉快~~
arXiv 2404.08441astro-ph.HEastro-ph.GA
收藏

超大质量黑洞周围吸积盘中的快速巨型耀发

Fast giant flares in discs around supermassive black holes

G. V. Lipunova, A. S. Tavleev, K. L. Malanchev

AI总结:

本文通过计算 SMBH 周围 α 盘平衡结构,发现冷盘环向热厚平流主导态转变可触发持续数年至数百年、接近或超爱丁顿光度的快速巨型耀发。

摘要:

我们研究了超大质量黑洞(SMBH)周围非自引力湍流 α 盘的热稳定性,以检验一种新型高振幅星系核耀发。通过计算盘结构,我们计算了 SMBH 周围吸积盘平衡曲线的临界点,这些临界点覆盖很宽的吸积率范围,形状类似 ξ。我们发现,盘环从复合冷态转变为炽热、完全电离、以平流为主且几何厚的状态是可能的。如果此前几何薄、光厚的吸积盘围绕着中心辐射低效吸积流,这种转变可在质量约为 10^6–10^8 M⊙ 的 SMBH 上触发巨型耀发。黏度参数 α 的增加是该情景的必要条件。这种增加可能与磁普朗特数在电离过程中增大并超过 1 有关。当盘中的自引力效应可忽略时,耀发的持续时间和功率与此前几何薄盘的截断半径呈正相关。根据我们的估计,如果耀发在质量为 10^7 M⊙ 的 SMBH 外 60 至 600 个引力半径之间的某处被触发,约 4–3000 M⊙ 的质量可参与持续 1 至 400 年的巨型耀发。SMBH 上的吸积率以约快 10 倍的速度达到峰值,并处于可能超爱丁顿的水平。光厚外流导致辐射各向异性。在巨型耀发开始时,截断半径附近区域被加热至约 10^5 K,其紫外/光学光度至少约为 0.3–4 L_Edd,具体取决于 SMBH 质量。SMBH 周围冷盘的突然加热可触发大规模爆发,其外观类似于潮汐瓦解事件之后被认为会发生的情况。

英文摘要:

We studied the thermal stability of non-self-gravitating turbulent $α$-discs around supermassive black holes (SMBHs) to test a new type of high-amplitude galactic nucleus flares. By calculating the disc structures, we computed the critical points of equilibrium curves for discs around SMBHs, which cover a wide range of accretion rates and resemble the shape $ξ$. We find that a transition of a disc ring from a recombined cold state to a hot, fully ionised, advection dominated, geometrically thick state is possible. Such a transition can trigger a giant flare for SMBHs with masses $\sim 10^6-10^8\, M_\odot$ if the prior geometrically thin and optically thick disc surrounded a central radiatively inefficient accretion flow. An increase in the viscosity parameter $α$ is a necessary condition for this scenario. This increase may be related to the fact that the magnetic Prandtl number increases and exceeds 1 during ionisation. When self-gravity effects in the disc are negligible, the duration and power of the flare exhibit a positive correlation with the prior truncation radius of the geometrically thin disc. According to our estimates, the mass of about $\sim 4-3000\, M_\odot$ can be involved in the giant flare lasting 1 to 400 years if the flare is triggered somewhere between $60$ and $600$ gravitational radii from the SMBH of $10^7\, M_\odot$. The accretion rate on the SMBH peaks about 10 times faster at the potentially super-Eddington level. An optically thick outflow leads to anisotropy of the emission. At the beginning of the giant flare, the region near the truncation radius is heated to $\sim 10^5\,$K, and its UV/optical luminosity is at least $\sim 0.3-4 \,L_\mathrm{Edd}$ depending on the SMBH mass. The sudden heating of a cold disc around a SMBH can trigger a massive outburst, similar in appearance to what is proposed to occur after a tidal disruption event.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑