A power-law break in the near-infrared power spectrum of the Galactic center black hole

Abstract

Proposed scaling relations of a characteristic timescale in the X-ray power spectral density of galactic and supermassive black holes have been used to argue that the accretion process is the same for small and large black holes. Here, we report on the discovery of this timescale in the near-infrared radiation of Sgr A*, the 4x10^6 solar mass black hole at the center of our Galaxy, which is the most extreme sub-Eddington source accessible to observations. Previous simultaneous monitoring campaigns established a correspondence between the X-ray and near-infrared regime and thus the variability timescales are likely identical for the two wavelengths. We combined Keck and VLT data sets to achieve the necessary dense temporal coverage, and a time baseline of four years allows for a broad temporal frequency range. Comparison with Monte Carlo simulations is used to account for the irregular sampling. We find a timescale at 154 (+124 -87) min (errors mark the 90% confidence limits) which is inconsistent with a recently proposed scaling relation that uses bolometric luminosity and black hole mass as parameters. However, our result fits the expected value if only linear scaling with black hole mass is assumed. We suggest that the luminosity-mass-timescale relation applies only to black hole systems in the soft state. In the hard state, which is characterized by lower luminosities and accretion rates, there is just linear mass scaling, linking Sgr A* to hard state stellar mass black holes.

14 pages; accepted by ApJ Letters for publication

References in corpus (8)

• Polarimetry of near-infrared flares from Sagittarius A*
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• A polarised infrared flare from Sagittarius A* and the signatures of orbiting plasma hotspots
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Cited by in corpus (17)

• Modeling the orbital motion of Sgr A*'s near-infrared flares
• Millimeter light curves of Sagittarius A* observed during the 2017 Event Horizon Telescope campaign
• Simulations of imaging the event horizon of Sagittarius A* from space
• Rapid Variability of Sgr A* across the Electromagnetic Spectrum
• Constraining particle acceleration in Sgr A* with simultaneous GRAVITY, Spitzer, NuSTAR and Chandra observations
• The X-ray Flux Distribution of Sagittarius A* as Seen by Chandra
• Gamma-ray Flux Distribution and Non-linear behavior of Four LAT Bright AGNs
• Spacetime Tomography Using The Event Horizon Telescope
• Spitzer/IRAC Observations of the Variability of Sgr A* and the Object G2 at 4.5 microns
• Quantifying Intrinsic Variability of Sagittarius A* using Closure Phase Measurements of the Event Horizon Telescope
• Time Variations in the Flux Density of Sgr A* at 230 GHz Detected with ALMA
• A formal method for identifying distinct states of variability in time-varying sources: SgrA* as an example
• Multi-wavelength Variability of Sagittarius A* in July 2019
• Time Domain Filtering of Resolved Images of Sgr A*
• Possible evidence from the flaring activity of Sgr A* for a star at a distance of ~3.3 Schwarzscild radii from the blackhole
• A 149 minute periodicity underlies the X-ray flaring of Sgr A*
• The orbit and nature of the semi-detached stellar companion of Sgr A* super-massive blackhole