Quantifying Intrinsic Variability of Sagittarius A* using Closure Phase Measurements of the Event Horizon Telescope

Abstract

General relativistic magnetohydrodynamic (GRMHD) simulations of accretion disks and jets associated with supermassive black holes show variability on a wide range of timescales. On timescales comparable to or longer than the gravitational timescale $t_G=GM/c^3$, variation may be dominated by orbital dynamics of the inhomogeneous accretion flow. Turbulent evolution within the accretion disk is expected on timescales comparable to the orbital period, typically an order of magnitude larger than $t_G$. For Sgr A*, $t_G$ is much shorter than the typical duration of a VLBI experiment, enabling us to study this variability within a single observation. Closure phases, the sum of interferometric visibility phases on a triangle of baselines, are particularly useful for studying this variability. In addition to a changing source structure, variations in observed closure phase can also be due to interstellar scattering, thermal noise, and the changing geometry of projected baselines over time due to Earth rotation. We present a metric that is able to distinguish the latter two from intrinsic or scattering variability. This metric is validated using synthetic observations of GRMHD simulations of Sgr A*. When applied to existing multi-epoch EHT data of Sgr A*, this metric shows that the data are most consistent with source models containing intrinsic variability from source dynamics, interstellar scattering, or a combination of those. The effects of black hole inclination, orientation, spin, and morphology (disk or jet) on the expected closure phase variability are also discussed.

18 pages, 15 figures; accepted for publication in ApJ

References in corpus (54)

• Monitoring stellar orbits around the Massive Black Hole in the Galactic Center
• Measuring Distance and Properties of the Milky Way's Central Supermassive Black Hole with Stellar Orbits
• Viewing the Shadow of the Black Hole at the Galactic Center
• Event-horizon-scale structure in the supermassive black hole candidate at the Galactic Centre
• HARM: A Numerical Scheme for General Relativistic Magnetohydrodynamics
• Nonthermal Electrons in Radiatively Inefficient Accretion Flow Models of Sagittarius A*
• Advection-Dominated Accretion Model of Sagittarius A*: Evidence for a Black Hole at the Galactic Center
• Testing the No-Hair Theorem with Observations in the Electromagnetic Spectrum: II. Black-Hole Images
• Apparent shape of super-spinning black holes
• General relativistic magnetohydrodynamical simulations of the jet in M87
• Radiative Models of Sgr A* from GRMHD Simulations
• Shapes and Positions of Black Hole Shadows in Accretion Disks and Spin Parameters of Black Holes
• An Unambiguous Detection of Faraday Rotation in Sagittarius A*
• High Resolution Linear Polarimetric Imaging for the Event Horizon Telescope
• Direct calculation of the radiative efficiency of an accretion disk around a black hole
• The Submillimeter Bump in Sgr A* from Relativistic MHD Simulations
• Resolved Magnetic-Field Structure and Variability Near the Event Horizon of Sagittarius A*
• An X-ray, IR, and Submillimeter Flare of Sagittarius A*
• 1.3 mm Wavelength VLBI of Sagittarius A*: Detection of Time-Variable Emission on Event Horizon Scales
• The old nuclear star cluster in the Milky Way: dynamics, mass, statistical parallax, and black hole mass
• BlackHoleCam: fundamental physics of the Galactic center
• Methods for detecting flaring structures in Sagittarius A* with high frequency VLBI
• Simulating the Emission and Outflows from Accretion Disks
• The size of the jet launching region in M87
• A Multi-Wavelength Study of Sgr A*: The Role of Near-IR Flares in Production of X-ray, Soft $\gamma$-ray and Sub-millimeter Emission
• A near-IR variability study of the Galactic black hole: a red noise source with no detected periodicity
• The Power of Imaging: Constraining the Plasma Properties of GRMHD Simulations using EHT Observations of Sgr A*
• Plasma diagnostic potential of 2p4f in N${}^{+}$ -- accurate wavelengths and oscillator strengths
• X-ray hiccups from SgrA* observed by XMM-Newton. The second brightest flare and three moderate flares caught in half a day
• A General Relativistic Null Hypothesis Test with Event Horizon Telescope Observations of the black-hole shadow in Sgr A*
• Towards the event horizon -- the supermassive black hole in the Galactic Center
• Radio and Millimeter Monitoring of Sgr A*: Spectrum, Variability, and Constraints on the G2 Encounter
• Coupled jet-disk model for Sgr A*: explaining the flat-spectrum radio core with GRMHD simulations of jets
• Modeling Seven Years of Event Horizon Telescope Observations with Radiatively Inefficient Accretion Flow Models
• Tilted black hole accretion disc models of Sagittarius A*: time-variable millimetre to near-infrared emission
• An 8 hour characteristic time-scale in submillimetre light curves of Sagittarius A*
• Theory and Simulations of Refractive Substructure in Resolved Scatter-Broadened Images
• Persistent Asymmetric Structure of Sagittarius A* on Event Horizon Scales
• Probing the magnetic field structure in Sgr A* on Black Hole Horizon Scales with Polarized Radiative Transfer Simulations
• ALMA and VLA measurements of frequency-dependent time lags in Sagittarius A*: evidence for a relativistic outflow
• Imaging an Event Horizon: Mitigation of Source Variability of Sagittarius A*
• Masses of Nearby Supermassive Black Holes with Very-Long Baseline Interferometry
• Detecting Changing Polarization Structures in Sagittarius A* with High Frequency VLBI
• Stochastic Optics: A Scattering Mitigation Framework for Radio Interferometric Imaging
• A power-law break in the near-infrared power spectrum of the Galactic center black hole
• Self-consistent spectra from radiative GRMHD simulations of accretion onto Sgr A*
• Using Millimeter VLBI to Constrain RIAF Models of Sagittarius A*
• The Optics of Refractive Substructure
• The Intrinsic Shape of Sagittarius A* at 3.5-mm Wavelength
• Asymmetric structure in Sgr A* at 3mm from closure phase measurements with VLBA, GBT and LMT
• Bayesian techniques for comparing time-dependent GRMHD simulations to variable Event Horizon Telescope observations
• Variability in GRMHD simulations of Sgr A${}^{\ast }$: Implications for EHT closure phase observations
• Probing spacetime around Sagittarius A* using modeled VLBI closure phases
• Measuring the Direction and Angular Velocity of a Black Hole Accretion Disk via Lagged Interferometric Covariance

Cited by in corpus (20)

• First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole
• First M87 Event Horizon Telescope Results. II. Array and Instrumentation
• First Sagittarius A* Event Horizon Telescope Results. III: Imaging of the Galactic Center Supermassive Black Hole
• First Sagittarius A* Event Horizon Telescope Results. II. EHT and Multi-wavelength Observations, Data Processing, and Calibration
• Simulations of imaging the event horizon of Sagittarius A* from space
• Dynamical Imaging with Interferometry
• Metrics and Motivations for Earth-Space VLBI: Time-Resolving Sgr A* with the Event Horizon Telescope
• Modified gravity black hole lensing observables in weak and strong field of gravity
• HI 21cm Cosmology and the Bi-spectrum: Closure Diagnostics in Massively Redundant Interferometric Arrays
• Decomposing the Internal Faraday Rotation of Black Hole Accretion Flows
• Silhouettes of invisible black holes
• Black hole parameter estimation with synthetic Very Long Baseline Interferometry data from the ground and from space
• To see invisible: image of the event horizon within the black hole shadow
• Event horizon silhouette: implications to supermassive black holes M87* and SgrA*
• The Variability of the Black-Hole Image in M87 at the Dynamical Time Scale
• First Space-VLBI Observations of Sagittarius A*
• Images and Spectra of Time Dependent Two Component Advective Flow in Presence of Outflows
• SYMBA: An end-to-end VLBI synthetic data generation pipeline
• Interferometric Closure Phase Uncertainties in the Low Signal-to-Noise Ratio Regime
• Visible shapes of black holes M87* and SgrA*