Self-consistent spectra from radiative GRMHD simulations of accretion on to Sgr A*

Drappeau, S.; Dibi, S.; Dexter, Jason; Markoff, Sera; Fragile, P. Chris

doi:10.1093/mnras/stt388

Cited by 45 publications

(56 citation statements)

References 81 publications

(107 reference statements)

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“…Specifically, we have studied the impact of realistic electron heating and electron thermal conduction on the spatial distribution of the electron temperature in 2D (axisymmetric) simulations of black hole accretion onto a rotating black hole. We find that the resulting electron temperatures differ significantly from the assumption of a constant electron to proton temperature ratio used in previous work to predict the emission from GRMHD simulations (Mościbrodzka et al 2009;Dibi et al 2012;Drappeau et al 2013);see, e.g. Figures 9-11.…”

Section: Discussioncontrasting

confidence: 75%

Electron thermodynamics in GRMHD simulations of low-luminosity black hole accretion

Ressler

Tchekhovskoy

Quataert

et al. 2015

Mon. Not. R. Astron. Soc.

171

238

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Simple assumptions made regarding electron thermodynamics often limit the extent to which general relativistic magnetohydrodynamic (GRMHD) simulations can be applied to observations of low-luminosity accreting black holes. We present, implement, and test a model that self-consistently evolves an entropy equation for the electrons and takes into account the effects of spatially varying electron heating and relativistic anisotropic thermal conduction along magnetic field lines. We neglect the back-reaction of electron pressure on the dynamics of the accretion flow. Our model is appropriate for systems accreting at ≪ 10 −5 of the Eddington accretion rate, so radiative cooling by electrons can be neglected. It can be extended to higher accretion rates in the future by including electron cooling and proton-electron Coulomb collisions. We present a suite of tests showing that our method recovers the correct solution for electron heating under a range of circumstances, including strong shocks and driven turbulence. Our initial applications to axisymmetric simulations of accreting black holes show that (1) physically-motivated electron heating rates that depend on the local magnetic field strength yield electron temperature distributions significantly different from the constant electron to proton temperature ratios assumed in previous work, with higher electron temperatures concentrated in the coronal region between the disc and the jet; (2) electron thermal conduction significantly modifies the electron temperature in the inner regions of black hole accretion flows if the effective electron mean free path is larger than the local scale-height of the disc (at least for the initial conditions and magnetic field configurations we study). The methods developed in this work are important for producing more realistic predictions for the emission from accreting black holes such as Sagittarius A* and M87; these applications will be explored in future work.

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Section: Discussioncontrasting

confidence: 75%

Electron thermodynamics in GRMHD simulations of low-luminosity black hole accretion

Ressler

Tchekhovskoy

Quataert

et al. 2015

Mon. Not. R. Astron. Soc.

171

238

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“…Sgr A * 's accretion rate is very low (Ṁ < 2 × 10 −7 M yr −1 ) as deduced from observations of polarization and Faraday rotation measurements (Bower et al 2003;Marrone et al 2007). This accretion rate is consistent with general relativistic magnetohydrodynamical (GRMHD) simulations that estimate a rate of a few times 10 −9 M yr −1 (Mościbrodzka et al 2009;Drappeau et al 2013). The bulk of the emission from Sgr A * is observed at radio and submillimeter frequencies, reaching a maximum of about 1 Jansky at the peak of the spectrum (e.g.…”

Section: Introductionsupporting

confidence: 87%

Using infrared/X-ray flare statistics to probe the emission regions near the event horizon of Sgr A*

Dibi

Markoff

Belmont

et al. 2016

Mon. Not. R. Astron. Soc.

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The supermassive black hole at the centre of the Galaxy flares at least daily in the infrared (IR) and X-ray bands, yet the process driving these flares is still unknown. So far detailed analysis has only been performed on a few bright flares. In particular, the broadband spectral modelling suffers from a strong lack of simultaneous data. However, new monitoring campaigns now provide data on thousands of flaring events, allowing a statistical analysis of the flare properties. In this paper, we investigate the X-ray and IR flux distributions of the flare events.Using a self-consistent calculation of the particle distribution, we model the statistical properties of the flares. Based on a previous work on single flares, we consider two families of models: pure synchrotron models and synchrotron self-Compton (SSC) models. We investigate the effect of fluctuations in some relevant parameters (e.g. acceleration properties, density, magnetic field) on the flux distributions. The distribution of these parameters is readily derived from the flux distributions observed at different wavelengths.In both scenarios, we find that fluctuations of the power injected in accelerated particles plays a major role. This must be distributed as a power-law (with different indices in each model). In the synchrotron dominated scenario, we derive the most extreme values of the acceleration power required to reproduce the brightest flares. In that model, the distribution of the acceleration slope fluctuations is constrained and in the SSC scenario we constrain the distributions of the correlated magnetic field and flow density variations.

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“…Mościbrodzka et al 2009;Dibi et al 2012;Drappeau et al 2013) and will be further constrained when the event horizon telescope is fully operational.…”

Section: Results: Agnmentioning

confidence: 99%

Black Hole Spin: Theory and Observation

Middleton¹

2016

Astrophysics and Space Science Library

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In the standard paradigm, astrophysical black holes can be described solely by their mass and angular momentum -commonly referred to as 'spin' -resulting from the process of their birth and subsequent growth via accretion. Whilst the mass has a standard Newtonian interpretation, the spin does not, with the effect of non-zero spin leaving an indelible imprint on the space-time closest to the black hole. As a consequence of relativistic frame-dragging, particle orbits are affected both in terms of stability and precession, which impacts on the emission characteristics of accreting black holes both stellar mass in black hole binaries (BHBs) and supermassive in active galactic nuclei (AGN). Over the last 30 years, techniques have been developed that take into account these changes to estimate the spin which can then be used to understand the birth and growth of black holes and potentially the powering of powerful jets. In this chapter we provide a broad overview of both the theoretical effects of spin, the means by which it can be estimated and the results of ongoing campaigns.

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Self-consistent spectra from radiative GRMHD simulations of accretion on to Sgr A*

Cited by 45 publications

References 81 publications

Electron thermodynamics in GRMHD simulations of low-luminosity black hole accretion

Electron thermodynamics in GRMHD simulations of low-luminosity black hole accretion

Using infrared/X-ray flare statistics to probe the emission regions near the event horizon of Sgr A*

Black Hole Spin: Theory and Observation

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