Shadows in dyonic Kerr-Sen black holes

Abstract

Black holes with dyonic charges in Einstein-Maxwell-dilaton-axion supergravity theory are revisited in the context of black hole shadows. We consider static as well as rotating (namely the dyonic Kerr-Sen) black holes. The matter stress-energy tensor components, sourced by the Maxwell, axion and dilaton fields satisfy the standard energy conditions. The analytical expressions for the horizon and the shadow radius of the static spacetimes demonstrate their dependence on $P^2+Q^2$ ($P$, $Q$ the magnetic and electric charges, respectively) and the mass parameter $M$. The shadow radius lies in the range $2M<R_{shadow}<3\sqrt{3}M$ and there is no stable photon orbit outside the horizon. Further, shadows cast by the rotating dyonic Kerr-Sen black holes are also studied and compared graphically with their Kerr-Newman and Kerr-Sen counterparts. Deviation of the shadow boundary is prominent with the variation of the magnetic charge, for the relatively slowly rotating dyonic Kerr-Sen spacetimes. We test any possible presence of a magnetic monopole charge in the backdrop of recent EHT observations for the supermassive black holes M87${}^{\ast }$ and Sgr A${}^{\ast }$. Deviation from circularity of the shadow boundary ($\Delta C$) and deviation of the average shadow radius from the Schwarzschild shadow radius (quantified as the fractional deviation parameter $\delta$) are the two observables used here. Observational bound on $\Delta C$ (available only for M87${}^{\ast }$) is satisfied for all theoretically allowed regions of parameter space and thus cannot constrain the parameters. The observational bound on $\delta$ available for Sgr A${}^{\ast }$ translates into an upper limit on any possible magnetic monopole charge linked to Sgr A${}^{\ast }$ and is given as $P\lesssim 0.873M$. Such a constraint on $P$ is however expected to be far more stringent for other astrophysical tests.

28 pages, 9 figures, published version

References in corpus (12)

• First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole
• First Sagittarius A* Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole in the Center of the Milky Way
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• First M87 Event Horizon Telescope Results. V. Physical Origin of the Asymmetric Ring
• First Sagittarius A* Event Horizon Telescope Results. VI: Testing the Black Hole Metric
• Black hole shadow in a general rotating spacetime obtained through Newman-Janis algorithm
• Hidden symmetries, null geodesics, and photon capture in the Sen black hole
• QED Effect on Black Hole Shadow
• Tests of Loop Quantum Gravity from the Event Horizon Telescope Results of Sgr A${}^{\ast }$
• Magnetic Monopole Search at high altitude with the SLIM experiment
• Testing black hole mimickers with the Event Horizon Telescope image of Sagittarius A${}^{\ast }$
• Black Holes with Multiple Photon Spheres

Cited by in corpus (4)

• Shadows and weak gravitational lensing by the black hole in Einstein-Maxwell-scalar theory
• Thin accretion disk and shadow of Kerr-Sen black hole in Einstein-Maxwell-dilaton-axion gravity
• New rotating Lorentzian wormhole spacetime
• Deciphering signatures of Kerr-Sen black holes in presence of plasma from the Event Horizon Telescope data