Machine learning on simulated images identifies that flux eruption events cause more diffuse, polarized, lower-flux millimeter emission with decreased Q-U loop rotation rate, achieving ~80% accuracy with random forests on summary statistics.
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Detection of orbital motions near the last stable circular orbit of the massive black hole SgrA*
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abstract
We report the detection of continuous positional and polarization changes of the compact source SgrA* in high states ('flares') of its variable near- infrared emission with the near-infrared GRAVITY-Very Large Telescope Interferometer (VLTI) beam-combining instrument. In three prominent bright flares, the position centroids exhibit clockwise looped motion on the sky, on scales of typically 150 micro-arcseconds over a few tens of minutes, corresponding to about 30% the speed of light. At the same time, the flares exhibit continuous rotation of the polarization angle, with about the same 45(+/-15)-minute period as that of the centroid motions. Modelling with relativistic ray tracing shows that these findings are all consistent with a near face-on, circular orbit of a compact polarized 'hot spot' of infrared synchrotron emission at approximately six to ten times the gravitational radius of a black hole of 4 million solar masses. This corresponds to the region just outside the innermost, stable, prograde circular orbit (ISCO) of a Schwarzschild-Kerr black hole, or near the retrograde ISCO of a highly spun-up Kerr hole. The polarization signature is consistent with orbital motion in a strong poloidal magnetic field.
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A perturbative framework for black holes in anisotropic matter shows quasinormal modes dominated by gravitational redshift while tidal Love numbers exhibit order-unity deviations including vanishing and negative values.
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*.
Bayesian fitting to mock GRAVITY data shows robust detection of secondary images from Sgr A* flares requires both an order-of-magnitude larger sample and astrometric uncertainties reduced to 40% of current levels for |ΔBIC| > 7.9.
Black-hole superradiance extracts energy via the ergoregion and can trigger instabilities with applications to dark matter, beyond-Standard-Model physics, and laboratory analogs.
Bayesian analysis shows current near-IR astrometry data cannot distinguish massive boson stars from Schwarzschild black holes for Sgr A*.
Polarization signatures from GRMHD simulations of black hole accretion can help probe disk, corona, and jet properties when combined with X-ray polarimetry observations.
citing papers explorer
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Identifying Observational Signatures of Flux Eruption Events in Supermassive Black Hole Accretion Flows with Machine Learning
Machine learning on simulated images identifies that flux eruption events cause more diffuse, polarized, lower-flux millimeter emission with decreased Q-U loop rotation rate, achieving ~80% accuracy with random forests on summary statistics.
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Quasinormal modes and tidal responses of black holes in generic anisotropic matter environments
A perturbative framework for black holes in anisotropic matter shows quasinormal modes dominated by gravitational redshift while tidal Love numbers exhibit order-unity deviations including vanishing and negative values.
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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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Detectability of secondary images from flares near Sgr A* with mock GRAVITY data
Bayesian fitting to mock GRAVITY data shows robust detection of secondary images from Sgr A* flares requires both an order-of-magnitude larger sample and astrometric uncertainties reduced to 40% of current levels for |ΔBIC| > 7.9.
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Superradiance -- the 2020 Edition
Black-hole superradiance extracts energy via the ergoregion and can trigger instabilities with applications to dark matter, beyond-Standard-Model physics, and laboratory analogs.
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Bayesian Analysis of Massive Boson Star Models for Sagittarius A* Using Near-Infrared Astrometry Data
Bayesian analysis shows current near-IR astrometry data cannot distinguish massive boson stars from Schwarzschild black holes for Sgr A*.
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Polarization Signatures from GRMHD Simulations of Black Hole Accretion
Polarization signatures from GRMHD simulations of black hole accretion can help probe disk, corona, and jet properties when combined with X-ray polarimetry observations.