Excavating black hole continuum spectrum: Possible signatures of scalar hairs and of higher dimensions

Abstract

Continuum spectrum from black hole accretion disc holds enormous information regarding the strong gravity regime around the black hole and hence about the nature of gravitational interaction in extreme situations. Since in such strong gravity regime the dynamics of gravity should be modified from the \EH one, its effect should be imprinted on the continuum spectrum originating from the black hole accretion. To explore the effects of these alternative theories on the black hole continuum spectrum in an explicit manner, we have discussed three alternative gravitational models having their origin in three distinct paradigms --- (a) higher dimensions, (b) higher curvature gravity and (c) Horndeski theories. All of them can have signatures sculptured on the black hole continuum spectrum, distinct from the standard general relativistic scenario. Interestingly all these models exhibit black hole solutions with tidal charge parameter which in these alternative gravity scenarios can become negative, in sharp contrast with the Reissner-Nordström black hole. Using the observational data of optical luminosity for eighty Palomer Green quasars we have illustrated that the difference between the theoretical estimates and the observational results gets minimized for negative values of the tidal charge parameter. As a quantitative estimate of this result we concentrate on several error estimators, including reduced ${\chi }^2$, Nash-Sutcliffe efficiency, index of agreement etc. Remarkably, all of them indicates a negative value of the tidal charge parameter, signaling the possibility of higher dimensions as well as scalar charge at play in those high gravity regimes.

v2, Revised, Published in PRD; 30 pages, 9 figures;

References in corpus (28)

• Dynamics of dark energy
• Unified cosmic history in modified gravity: from F(R) theory to Lorentz non-invariant models
• The Confrontation between General Relativity and Experiment
• Covariant Galileon
• Modified f(R) gravity consistent with realistic cosmology: from matter dominated epoch to dark energy universe
• Cosmological viability of f(R)-gravity as an ideal fluid and its compatibility with a matter dominated phase
• Healthy theories beyond Horndeski
• Sizes and Temperature Profiles of Quasar Accretion Disks from Chromatic Microlensing
• Multi-field galileons and higher co-dimension branes
• Asymptotically locally AdS and flat black holes in the presence of an electric field in the Horndeski scenario
• Deflection angle in the strong deflection limit in a general asymptotically flat, static, spherically symmetric spacetime
• Profiles of emission lines generated by rings orbiting braneworld Kerr black holes
• Host dynamics and origin of Palomar-Green QSOs
• Charged Galileon black holes
• Time-dependent spherically symmetric covariant Galileons
• Spherically symmetric brane spacetime with bulk $f(\mathcal{R})$ gravity
• Constraining some Horndeski gravity theories
• Matter without matter: novel Kaluza-Klein spacetime in Einstein-Gauss-Bonnet gravity
• Gravitational Lensing by Self-Dual Black Holes in Loop Quantum Gravity
• Strong gravitational lensing across dilaton anti-de Sitter black hole
• Evolution of Spacetime arises due to the departure from Holographic Equipartition in all Lanczos-Lovelock Theories of Gravity
• Efficiency of the Keplerian accretion in the Braneworld Kerr--Newman Spacetimes and mining instability of some naked singularity spacetimes
• Geometrical variables with direct thermodynamic significance in Lanczos-Lovelock gravity
• Host Galaxies of Luminous Quasars: Structural Properties and the Fundamental Plane
• Low energy effective gravitational equations on a Gauss-Bonnet brane
• From Lovelock to Horndeski's generalised scalar-tensor theory
• Observing a Black Hole Event Horizon: (Sub)Millimeter VLBI of Sgr A*
• Toward a Unified AGN Structure