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First Sagittarius A* Event Horizon Telescope Results. IV. Variability, Morphology, and Black Hole Mass

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arxiv 2311.08697 v1 pith:RS37KHPP submitted 2023-11-15 astro-ph.HE

The Event Horizon Telescope Collaboration This is my paper · ORCID
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keywords datavariabilityfitsmodelsringdiametergeometricsource
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abstract

In this paper we quantify the temporal variability and image morphology of the horizon-scale emission from Sgr A*, as observed by the EHT in 2017 April at a wavelength of 1.3 mm. We find that the Sgr A* data exhibit variability that exceeds what can be explained by the uncertainties in the data or by the effects of interstellar scattering. The magnitude of this variability can be a substantial fraction of the correlated flux density, reaching $\sim$100\% on some baselines. Through an exploration of simple geometric source models, we demonstrate that ring-like morphologies provide better fits to the Sgr A* data than do other morphologies with comparable complexity. We develop two strategies for fitting static geometric ring models to the time-variable Sgr A* data; one strategy fits models to short segments of data over which the source is static and averages these independent fits, while the other fits models to the full dataset using a parametric model for the structural variability power spectrum around the average source structure. Both geometric modeling and image-domain feature extraction techniques determine the ring diameter to be $51.8 \pm 2.3$ $\mu$as (68\% credible intervals), with the ring thickness constrained to have an FWHM between $\sim$30\% and 50\% of the ring diameter. To bring the diameter measurements to a common physical scale, we calibrate them using synthetic data generated from GRMHD simulations. This calibration constrains the angular size of the gravitational radius to be $4.8_{-0.7}^{+1.4}$ \mathrm{\mu as}, which we combine with an independent distance measurement from maser parallaxes to determine the mass of Sgr A* to be $4.0_{-0.6}^{+1.1} \times 10^6$ M$_{\odot}$.

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Cited by 7 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

  1. Signatures of Lorentz violation in bright ring for Sgr A* images by radiation ineffective accretion flows

    astro-ph.HE 2026-08 conditional novelty 6.0 of 10

    For a rotating Lorentz-violating black hole, increasing the LV parameter shrinks and broadens Sgr A*'s image ring, and EHT data bound the parameter over a spin-dependent range.

  2. Dark matter environments and safeguards for spacetime inference from horizon scale interferometry

    gr-qc 2026-07 conditional novelty 6.0 of 10

    Using public 2017 M87* closure data, a frozen Kerr source fails an absolute adequacy test and the differential tidal-charge response fails numerical convergence, so no posterior or bound is reported.

  3. Constructing a gravitational wave analysis pipeline for extremely large mass ratio inspirals

    astro-ph.HE 2026-01 conditional novelty 6.0 of 10

    A hierarchical semi-coherent F-statistic plus particle-swarm pipeline recovers an injected Sgr A* XMRI from 90 days of simulated TianQin data with sub-percent parameter precision.

  4. Photon Propagation and Black Hole Imaging in Kruglov Nonlinear Electrodynamics

    gr-qc 2026-04 unverdicted novelty 5.0 of 10

    In Kruglov's Born-Infeld-type nonlinear electrodynamics, the effective photon geometry around a charged black hole produces q-dependent shifts in light deflection, shadow radius, and accretion disk images, including s...

  5. Observational Constraints on Kazakov-Solodukhin Quantum-Deformed Black Holes from M87$^*$ and Sgr A$^*$ Shadows

    gr-qc 2026-07 conditional novelty 4.0 of 10

    EHT shadow sizes of M87* and Sgr A* constrain the Kazakov-Solodukhin deformation parameter η to O(1) ranges while the metric remains asymptotically Schwarzschild.

  6. Plasma effects on gravitational lensing and shadow observables of a Kerr-like black hole in a dark matter halo

    gr-qc 2026-03 conditional novelty 4.0 of 10

    Homogeneous plasma enlarges Kerr-like black-hole shadows and emission rates while inhomogeneous plasma shrinks them; astrophysical dark-matter densities leave photon orbits essentially unchanged.

  7. Thermodynamics and Shadows of Kerr black holes endowed with a global monopole charge

    gr-qc 2025-06 reject novelty 4.0 of 10

    The authors derive shadow and thermodynamic quantities for a Kerr-like metric with a global monopole term in Δ, and claim EHT observations constrain the monopole charge α.

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