Time-Dependent Models of Flares From Sagittarius A*

Dodds-Eden, K.; Sharma, Prateek; Quataert, Eliot; Genzel, R.; Gillessen, S.; Eisenhauer, F.; Porquet, D.

doi:10.1088/0004-637x/725/1/450

Cited by 107 publications

(157 citation statements)

References 66 publications

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“…This limit was obtained from measurements that are simultaneous with flare observations (Dodds-Eden et al 2010). The spectral index of α = +0.15 that would meet the limit, is too flat.…”

Section: An Adiabatic Expansion Model Of the May 2009 Datamentioning

confidence: 99%

“…Dodds-Eden et al (2009) modeled a single, exceptionally bright X-ray flare event using a pure synchrotron description. This illustrates that the need to include as little as possible a SSC contribution to the predicted X-ray flux places stringent constraints on the pure synchrotron model (Dodds-Eden et al 2010).…”

Section: The Synchrotron Cutoff Frequency νmentioning

confidence: 99%

“…4.3). While the 11.88 μm flux density limit (Dodds-Eden et al 2010; see comments by Schödel et al 2011) is included in the uncertainties quoted for model "B I" in Eckart et al (2008; with or without correction of A L ), model "ABαφ3" in does violate this MIR limit. MIR emission in excess of this 11.88 μm limit is also produced by "Model I" for flare A in Trap et al (2010).…”

Section: Mir Flux Limitmentioning

confidence: 99%

“…Baganoff et al (2003) detected a very low quiescent X-ray luminosity. At infrared wavelengths, the possible presence of a quiescent state is currently under investigation (see discussion in Schödel et al 2011;Do et al 2009;Sabha et al 2010;Dodds-Eden et al 2010). The submm spectrum of SgrA* itself is not very well-known owing to resolution effects and the contaminating flux density contributions from the surrounding "mini-spiral" HII region and the circumnuclear disk (CND).…”

Section: Introductionmentioning

confidence: 99%

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Millimeter to X-ray flares from Sagittarius A*

Eckart

García-Marín

Vogel

et al. 2012

A&A

146

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Context. We report on new simultaneous observations and modeling of the millimeter, near-infrared, and X-ray flare emission of the source Sagittarius A* (SgrA*) associated with the super-massive (4 × 10 6 M ) black hole at the Galactic center. Aims. We study the applicability of the adiabatic synchrotron source expansion model and study physical processes giving rise to the variable emission of SgrA* from the radio to the X-ray domain. Methods. Our observations were carried out on 18 May 2009 using the NACO adaptive optics (AO) instrument at the European Southern Observatory's Very Large Telescope, the ACIS-I instrument aboard the Chandra X-ray Observatory, the LABOCA bolometer at the Atacama Pathfinder EXperiment (APEX), and the CARMA mm telescope array at Cedar Flat, California. Results. The X-ray flare had an excess 2−8 keV luminosity between 6 and 12×10 33 erg s −1 . The observations reveal flaring activity in all wavelength bands that can be modeled as the signal from an adiabatically expanding synchrotron self-Compton (SSC) component.Modeling of the light curves shows that the sub-mm follows the NIR emission with a delay of about three-quarters of an hour with an expansion velocity of about v exp ∼ 0.009c. We find source component sizes of around one Schwarzschild radius, flux densities of a few Janskys, and spectral indices α of about +1 (S (ν) ∝ ν −α ). At the start of the flare, the spectra of the two main components peak just short of 1 THz. To statistically explain the observed variability of the (sub-)mm spectrum of SgrA*, we use a sample of simultaneous NIR/X-ray flare peaks and model the flares using a synchrotron and SSC mechanism. Conclusions. These parameters suggest that either the adiabatically expanding source components have a bulk motion larger than v exp or the expanding material contributes to a corona or disk, confined to the immediate surroundings of SgrA*. For the bulk of the synchrotron and SSC models, we find synchrotron turnover frequencies in the range of 300−400 GHz. For the pure synchrotron models, this results in densities of relativistic particles of the order of 10 6.5 cm −3 and for the SSC models, the median densities are about one order of magnitude higher. However, to obtain a realistic description of the frequency-dependent variability amplitude of SgrA*, models with higher turnover frequencies and even higher densities are required.

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“…This limit was obtained from measurements that are simultaneous with flare observations (Dodds-Eden et al 2010). The spectral index of α = +0.15 that would meet the limit, is too flat.…”

Section: An Adiabatic Expansion Model Of the May 2009 Datamentioning

confidence: 99%

Section: The Synchrotron Cutoff Frequency νmentioning

confidence: 99%

Section: Mir Flux Limitmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Millimeter to X-ray flares from Sagittarius A*

Eckart

García-Marín

Vogel

et al. 2012

A&A

146

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“…Observations and models agree on the fact that synchrotron emission by non-thermal relativistic electrons can account for the IR flares, but what exactly triggers electron acceleration is not modelled in detail and is therefore subject to interpretation (see e.g. Markoff et al 2001;Yuan et al 2003;Tagger & Melia 2006;Yuan et al 2009;Dodds-Eden et al 2010;Zubovas & Nayakshin 2012;Dibi et al 2014). …”

Section: Introductionmentioning

confidence: 99%

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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Tests with Other Approaches

Bambi

2017

Black Holes: A Laboratory for Testing Strong Gravity

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Time-Dependent Models of Flares From Sagittarius A*

Cited by 107 publications

References 66 publications

Millimeter to X-ray flares from Sagittarius A*

Millimeter to X-ray flares from Sagittarius A*

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

Tests with Other Approaches

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