2024/08/07 by Chan, Ho-Sang, Chan, Chi-kwan · 1 citation
#FOS: Physical sciences #General Relativity and Quantum Cosmology (gr-qc) #High Energy Astrophysical Phenomena (astro-ph.HE)
paper · doi:10.48550/arxiv.2408.04132
We continue our previous work, Chan et al. 2024, to investigate how variations in the electron temperature prescription parameter, R\rm Low, influence the 3-hour variability at 230 GHz, MΔT, in magnetic-arrested disk (MAD) models of Sagittarius~A* (Sgr~A*), through analyzing a series of general-relativistic magnetohydrodynamics and raytracing simulations. For models with a black hole spin a > 0, we discovered that increasing R\rm Low renders the photon ring more optically thick, obscuring the varying accretion flows that contribute to the variability. However, as R\rm Low increases further, MAD flux eruptions become more pronounced, compensating for the decrease in MΔT. For models with a spin a < 0, although a higher R\rm Low also increases the optical thickness of the fluid, voids within the optically thick gas fail to cover the entire photon ring. Similarly, flux eruptions become more prominent as R\rm Low increases further, contributing to the observed rise in MΔT relative to R\rm Low. For black holes with a spin a = 0, although the effect of increasing optical depth is still present, their 230 GHz light curves, and hence MΔT, are insensitive to changes in R\rm Low. Furthermore, we found that the variability of the 230 GHz light curves at R\rm Low = 1 might correlate with fluctuations in the internal energy of the gas near the black hole, and we listed potential causes and solutions to the over-variability problem. Our findings highlight potential approaches for refining MΔT to better align with observations when modeling Sgr~A*.