Inspiraling hotspots in Kerr spacetime produce precessing unwinding Stokes Q-U loops in polarization, unlike the closed loops from fixed-radius orbits.
Imaging Optically-Thin Hot Spots Near the Black Hole Horizon of Sgr A* at Radio and Near-Infrared Wavelengths
4 Pith papers cite this work. Polarity classification is still indexing.
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abstract
Sub milli-arcsecond astrometry and imaging of the black hole Sgr A* at the Galactic centre may become possible in the near future at infrared and sub-millimetre wavelengths. Motivated by observations of short-term infrared and X-ray variability of Sgr A*, in a previous paper we computed the expected images and light curves, including polarization, associated with an compact emission region orbiting the central black hole. We extend this work, using a more realistic hot-spot model and including the effects of opacity in the underlying accretion flow. We find that at infrared wavelengths the qualitative features identified by our earlier work are present, namely it is possible to extract the black hole mass and spin from spot images and light curves of the observed flux and polarization. At radio wavelengths, disk opacity produces significant departures from the infrared behaviour, but there are still generic signatures of the black hole properties. Detailed comparison of these results with future data can be used to test general relativity and to improve existing models for the accretion flow in the immediate vicinity of the black hole.
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Corotating point sources on accretion disks near black holes distort the relative magnification factor distribution, modulating caustics and encoding accretion flow kinematics via time-delayed images.
Fitting GRAVITY flare astrometry to solitonic boson star models requires masses larger than 4.3 million solar masses, with more diffuse models yielding values closer to the standard black hole mass and thus placing stringent but incomplete constraints on such interpretations of Sgr A*.
Current and future observations can test whether dark compact objects are Kerr black holes or exotic alternatives, with null results strengthening the black hole paradigm.
citing papers explorer
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Polarization Signatures of Inspiraling Hotspots around Kerr Black Holes
Inspiraling hotspots in Kerr spacetime produce precessing unwinding Stokes Q-U loops in polarization, unlike the closed loops from fixed-radius orbits.
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Relative Magnification Factor of Point Sources on Accretion Disks
Corotating point sources on accretion disks near black holes distort the relative magnification factor distribution, modulating caustics and encoding accretion flow kinematics via time-delayed images.
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Testing solitonic boson star interpretations of Sagittarius A* with near-infrared flare astrometry
Fitting GRAVITY flare astrometry to solitonic boson star models requires masses larger than 4.3 million solar masses, with more diffuse models yielding values closer to the standard black hole mass and thus placing stringent but incomplete constraints on such interpretations of Sgr A*.
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Testing the nature of dark compact objects: a status report
Current and future observations can test whether dark compact objects are Kerr black holes or exotic alternatives, with null results strengthening the black hole paradigm.