High Energy Astrophysical Phenomena (astro-ph.HE)

Abstract: In the paper, a comparative primary cosmic rays (PCR) comparative analysis by $E_0$ and the spectra of variable stars by periods is carried out in order to establish the causes of irregularities in the spectrum of PCR by $E_0$. The study was performed using the public database of the KASCADE-Grande experiment and GCVS and ZTF variable star catalogues. It has been suggested that the acceleration of PCR to high and super-high energies occurs not only on the shock waves of supernovae, but also in bursts of giants and super-giants. The relationship between the periods of variable stars and the maximum energy $E_0$ of the nuclei of PCRs generated by these types of stars is shown. Irregularities in the PCR spectrum by $E_0$ are associated with the transition from one dominant stars type to another as $E_0$ increases. The knee in the PCR spectrum at $E_0~=~3-5~PeV$ is associated with a decrease in the contribution of SRB variability stars and a further increase in the contribution of Mira variable stars to the PCR flux. The bump in the PCR spectrum with a maximum at $E_0~=~80~PeV$, established in the KASCADE-Grande experiment, is formed by giant stars and super-giants of the Mira and SRC variability.

Abstract: We solve the full quasilinear kinetic equation governing nonresonant interactions of Alfv\'en waves with relativistic plasmas. This work was motivated by the need to determine the energy available for the synchrotron maser in the context of Fast Radio Bursts (FRBs). This interaction can result in plasma heating and the formation of population inversions necessary for the maser. We find that population inversions containing $\sim 1-10\%$ of the distribution's energy form in the relativistic regime, providing an explanation for the formation of the inversion in the environment expected near FRBs.

Abstract: Large-scale magnetic fields in the nuclear regions of protogalaxies can trigger the formation and early growth of supermassive black holes (SMBHs) by direct collapse and boosted accretion. Turbulence associated with gravitational infall and star formation can drive the rms field strength toward equipartition with the mean gas kinetic energy; this field has a generic tendency to self-organize into large, coherent structures. If the poloidal component of the field (relative to the rotational axis of a star-forming disc) becomes organized on scales $\lesssim r$ and attains an energy of order a few percent of the turbulent energy in the disc, then dynamo effects are expected to generate magnetic torques capable of boosting the inflow speed and thickening the disk. The accretion flow can transport matter toward the center of mass at a rate adequate to create and grow a massive direct-collapse black hole (DCBH) seed and fuel the subsequent AGN at a high rate, without becoming gravitationally unstable. Fragmentation and star formation are thus suppressed and do not necessarily deplete the mass supply for the accretion flow, in contrast to prevailing models for growing and fueling SMBHs through disc accretion.

Abstract: We revisit the precessing black hole binary model, a candidate to explain the bizarre quasi-periodic optical flares in OJ-287's light curve, from first principles. We deviate from existing work in three significant ways: 1) Including crucial aspects of relativistic dynamics related to the accretion disc's gravitational moments. 2) Adopting a model-agnostic prescription for the disc's density and scale height. 3) Using monte-carlo Markhov-chain methods to recover reliable system parameters and uncertainties. We showcase our model's predictive power by timing the 2019 great Eddington flare within 40 hr of the observed epoch, exclusively using data available prior to it. Additionally, we obtain a novel direct measurement of OJ-287's disc mass and quadrupole moment exclusively from the optical flare timings. Our improved methodology can uncover previously unstated correlations in the parameter posteriors and patterns in the flare timing uncertainties. In contrast to the established literature, we predict the 26th optical flare to occur on the 21st of August 2023 $\pm$ 32 days, shifted by almost a year with respect to the alleged "missing" flare of October 2022.