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تسجيل مستخدم جديدAccretion-modified Stars in Accretion Disks of Active Galactic Nuclei: Slowly Transient Appearance
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Compact objects are expected to exist in the accretion disks of supermassive black holes (SMBHs) in active galactic nuclei (AGNs), and in the presence of such a dense environment ($sim 10^{14},{rm cm^{-3}}$), they will form a new kind of stellar population denoted as Accretion-Modified Stars (AMSs). This hypothesis is supported by recent LIGO/Virgo detection of the mergers of very high-mass stellar binary black holes (BHs). We show that the TZOs will be trapped by the SMBH-disk within a typical AGN lifetime. In the context of SMBH-disks, the rates of Bondi accretion onto BHs are $sim 10^{9}L_{rm Edd}/c^{2}$, where $L_{rm Edd}$ is the Eddington luminosity and $c$ is the speed of light. Outflows developed from the hyper-Eddington accretion strongly impact the Bondi sphere and induce episodic accretion. We show that the hyper-Eddington accretion will be halted after an accretion interval of $t_{rm a}sim 10^{5}m_{1},$s, where $m_{1}=m_{bullet}/10sunm$ is the BH mass. The kinetic energy of the outflows accumulated during $t_{rm a}$ is equivalent to 10 supernovae driving an explosion of the Bondi sphere and developing blast waves. We demonstrate that a synchrotron flare from relativistic electrons accelerated by the blast waves peaks in the soft X-ray band ($sim 0.1,$keV), significantly contributing to the radio, optical, UV, and soft X-ray emission of typical radio-quiet quasars. External inverse Compton scattering of the electrons peaks around $40,$GeV and is detectable through {it Fermi}-LAT. The flare, decaying with $t^{-6/5}$ with a few months, will appear as a slowly varying transient. The flares, occurring at a rate of a few per year in radio-quiet quasars, provide a new mechanism for explaining AGN variability.
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