Abstract
Rotating black holes (BHs) are likely the largest energy reservoirs in the Universe as predicted by BH thermodynamics, while cosmic rays (CRs) are the most energetic among particles detected on Earth. Magnetic fields surrounding BHs combined with strong gravity effects, thanks to the spacetime symmetries, turn the BHs into powerful accelerators of charged particles. At the same time, in the age of multi-wavelength and multi-messenger astronomy, BHs and their environments have not yet been probed with CR messengers, despite being observed across most of the electromagnetic spectrum, and neutrino and gravitational waves. In this paper, we probe the acceleration capabilities of BHs in 8 galactic X-ray binaries and 25 local active galactic nuclei (AGNs) within 100 Mpc, based on the ultra-efficient regime of the magnetic Penrose process of a BH energy extraction combined with observational data. We find that the maximum energy of the galactic BHs can reach only up to the knee of the CR spectrum, including supermassive BH Sgr A* at the Galactic Center. On the other hand, for supermassive BHs in AGNs, we find that the mean energy of primary CRs is of the order of 1019 eV. It is therefore likely that local supermassive BHs give sufficient contribution to the ankle—a sharp change in the slope of the cosmic ray spectrum around 1018.6 eV energy. We also discuss the energy losses of primary CRs close to the acceleration zones. In the galactic BH cases, it is likely dominated by synchrotron radiation losses.
Highlights
Cosmic rays (CRs) are high-energy charged particles moving through the Universe with enormous velocities; when hitting Earth’s atmosphere, they produce air showers of secondary particles, allowing their detection at the surface
Using the available observational data, we constrain the energy of primary CRs originated from X-ray binary systems containing stellar mass black holes (BHs) and compare the results with those related to supermassive black holes (SMBH)
Magnetosphere of Rotating BHs: Magnetic Field—BH Mass Relation. Both stellar and supermassive, are usually surrounded by accretion disks constituted from highly ionized plasma, which gives rise to the generation of magnetic fields due to electric currents floating in the plasma
Summary
Cosmic rays (CRs) are high-energy charged particles (primarily protons) moving through the Universe with enormous velocities; when hitting Earth’s atmosphere, they produce air showers of secondary particles, allowing their detection at the surface. Interactions of high-energy protons (at energies above ∼1019.5 eV) during propagation along the large distances exceeding 100 Mpc with the cosmic microwave background photons put the limit on the maximum arrival energy of primary cosmic ray protons [2] This prediction of the standard model of particle physics is known as the GZK cutoff [3,4]. The shock acceleration in relativistic jets is among long-standing astrophysical scenarios [8] Another acceleration model was recently proposed [9], which attempts to explain UHECRs by the extraction of energy from rotating supermassive black holes (SMBH) through the so-called magnetic Penrose process. We extend our previous studies related to supermassive BHs [9] to stellar mass BHs. Using the available observational data, we constrain the energy of primary CRs originated from X-ray binary systems containing stellar mass BHs and compare the results with those related to SMBH.
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