Testing the nature of the supermassive black hole candidate in SgrA* with light curves and images of hot spots

Abstract

General relativity makes clear predictions about the spacetime geometry around black holes. In the near future, new facilities will have the capability to explore the metric around SgrA${}^{\ast }$, the supermassive black hole candidate at the Center of our Galaxy, and open a new window to test the Kerr black hole hypothesis. In this paper, we compute light curves and images associated with compact emission regions (hot spots) orbiting around Kerr and non-Kerr black holes. We study how the analysis of the properties of the radiation emitted by a hot spot can be used to test the Kerr nature of SgrA${}^{\ast }$. We find that the sole observation of the hot spot light curve can at most constrain a combination of the black hole spin and of possible deviations from the Kerr solution. This happens because the same orbital frequency around a Kerr black hole can be found for a non-Kerr object with a different spin parameter. Second order corrections in the light curve due to the background geometry are typically too small to be identified. While the observation of the hot spot centroid track can potentially bound possible deviations from the Kerr solution, that is out of reach for the near future VLTI instrument GRAVITY. The Kerr black hole hypothesis could really be tested in the case of the discovery of a radio pulsar in a compact orbit around SgrA${}^{\ast }$. Radio observations of such a pulsar would provide precise estimates of the mass and the spin of SgrA${}^{\ast }$, and the combination of these measurements (probing the weak field) with the hot spot light curve information (probing the strong field) may constrain/find possible deviations from the Kerr solution with quite good precision.

16 pages, 14 figures. v3: refereed version

References in corpus (20)

• Event-horizon-scale structure in the supermassive black hole candidate at the Galactic Centre
• Advection-Dominated Accretion and the Black Hole Event Horizon
• A Metric for Rapidly Spinning Black Holes Suitable for Strong-Field Tests of the No-Hair Theorem
• Apparent shape of super-spinning black holes
• Observing the shadow of Einstein-Maxwell-Dilaton-Axion black hole
• Null geodesics and shadow of a rotating black hole in extended Chern-Simons modified gravity
• Shadow of a Kaluza-Klein rotating dilaton black hole
• Flaring Activity of Sgr A* at 43 and 22 GHz: Evidence for Expanding Hot Plasma
• A code to compute the emission of thin accretion disks in non-Kerr space-times and test the nature of black hole candidates
• Shape and position of the shadow in the $\delta =2$ Tomimatsu-Sato space-time
• Towards the event horizon -- the supermassive black hole in the Galactic Center
• A polarised infrared flare from Sagittarius A* and the signatures of orbiting plasma hotspots
• Probing the space-time geometry around black hole candidates with the resonance models for high-frequency QPOs and comparison with the continuum-fitting method
• Perturbed Kerr Black Holes can probe deviations from General Relativity
• Time Dependent Models of Flares from Sagittarius A*
• Light Curves from an MHD Simulation of a Black Hole Accretion Disk
• Broad K$\alpha$ iron line from accretion disks around traversable wormholes
• GRAVITY: getting to the event horizon of Sgr A*
• Testing the Bardeen metric with the black hole candidate in Cygnus X-1
• Periodic Modulations in an X-ray Flare from Sagittarius A*

Cited by in corpus (20)

• Testing black hole candidates with electromagnetic radiation
• Constraining the spin and the deformation parameters from the black hole shadow
• Black Hole Based Tests of General Relativity
• Sgr A* and General Relativity
• Constraints on the spacetime geometry around 10 stellar-mass black hole candidates from the disk's thermal spectrum
• Testing the No-Hair Theorem with Observations of Black Holes in the Electromagnetic Spectrum
• Distinguishing black holes and wormholes with orbiting hot spots
• Shadows of CPR black holes and tests of the Kerr metric
• Using iron line reverberation and spectroscopy to distinguish Kerr and non-Kerr black holes
• Kerr black hole parameters in terms of red/blue shifts of photons emitted by geodesic particles
• Efficiency of the Keplerian accretion in the Braneworld Kerr--Newman Spacetimes and mining instability of some naked singularity spacetimes
• Physical laboratory at the center of the Galaxy
• Variations in emission from episodic plasmoid ejecta around black holes
• Strong deflection lensing by charged black holes in scalar-tensor gravity
• Note on the Cardoso-Pani-Rico parametrization to test the Kerr black hole hypothesis
• Testing a class of non-Kerr metrics with hot spots orbiting SgrA${}^{\ast }$
• Constraining the Cardoso-Pani-Rico metric with future observations of SgrA${}^{\ast }$
• Observational signatures from higher-order images of moving hotspots in accretion disks
• Auto- and cross-correlations for multiple images of corotating hotspots in accretion disks
• Sagittarius A* near-infrared flares polarization as a probe of space-time I: Non-rotating exotic compact objects