Accreting black holes are believed to be sites of possible particleacceleration with favorable conditions also for effective gamma-ray production.However, because of photon-photon pair production, only low energy (MeV)gamma-rays can escape these compact objects with typically very largecompactness parameter, given that in most cases the accretion disks within 10Schwarzschild radii radiate with a power exceeding 10 percent of the Eddingtonluminosity. Therefore, the high-energy gamma-ray emission of these objects(both stellar mass and supermassive BHs) is generally suppressed, andconsequently the unique information on possible particle acceleration processnear the event horizon of the BH is essentially lost. Fortunately, this is notthe case for the super-massive BH located at the dynamical center of our Galaxy(Sgr A*) which, thanks to its extraordinary low bolometric luminosity istransparent fo gamma-rays up to very high energies, about 10 TeV. We discussdifferent scenarios of gamma-ray production in Sgr A* and show that for areasonable set of parameters one can expect detectable gamma-ray fluxes of bothhadronic and electronic origin. Some of these scenarios are applicable not onlyfor the TeV gamma-ray emission recently reported from the direction of GalacticCenter, but may have broader implications relevant to highly variablenonthermal emission of Sgr A* in radio, IR and X-ray bands.
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机译：人们认为，积聚黑洞是可能的粒子加速的场所，同时也具有有效产生伽马射线的有利条件。但是，由于产生了光子-光子对，只有低能（MeV）的伽马射线才能以非常大的紧凑性逃逸这些紧凑的物体参数，因为在大多数情况下，10 Schwarzschild半径内的吸积盘辐射的功率超过了Eddingtonluminusity的10％。因此，通常会抑制这些物体（恒星质量和超质量BHs）的高能伽马射线发射，因此，在BH的事件视界附近，有关可能的粒子加速过程的唯一信息基本上会丢失。幸运的是，位于我们银河系（Sgr A *）动力学中心的超大质量BH并非如此，由于其极低的辐射热亮度，它是高达10 TeV的高能透明γ射线。我们讨论了Sgr A *中产生伽马射线的不同情况，并表明对于一组合理的参数集，人们可以预期可检测到的强子射线和电子源的伽马射线通量。这些场景中的某些场景不仅适用于GalacticCenter方向最近报告的TeV伽玛射线发射，而且可能与无线电，IR和X射线波段中Sgr A *高度可变的非热发射有关，具有更广泛的含义。
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