Circular orbits and QPOs near Kiselev black holes in f(R,T) gravity
Аннотация
Exploring the interaction of quintessence fields with black hole spacetimes in modified gravity theories can shed light on both dark energy phenomenology and gravity tests. In this work, we investigate static, spherically symmetric Kiselev black holes embedded in the framework of f(R,T) gravity, characterized by quintessence parameters K and gamma. We first analyze the existence and behavior of the event and Cauchy horizons as functions of (K, gamma). We then compute the scalar curvature invariants—the Ricci scalar R, the Ricci tensor square R_mu_nu R_mu_nu, and the Kretschmann scalar R_mu_nu_rho_sigma R_mu_nu_rho_sigma—to assess spacetime regularity and singularity structure. Investigating electrically neutral test particles, we derive the effective potential V_eff(r), the specific energy E_c and angular momentum L_c for circular orbits, and determine the radii of the innermost stable circular orbit (ISCO), the marginally bound orbit (MBO), and the minimum circular orbit (MCO) as functions of gamma. Next, we calculate the fundamental orbital (nu_K), radial (nu_r), and vertical (nu_theta) oscillation frequencies along these orbits and apply three leading quasi-periodic oscillation (QPO) models—relativistic precession, epicyclic resonance, and warped-disk—to predict upper and lower QPO frequencies. Finally, employing a Markov Chain Monte Carlo (MCMC) analysis with observed twin-peak QPO data from GRO J1655–40, GRS 1915+105, M82 X-1, and Sgr A*, we place simultaneous constraints on the black hole mass M, quintessence parameter K, state parameter gamma, and radial coordinate r.