Simultaneous HESS and Chandra observations of Sagitarius A$^{\star}$   during an X-ray flare

Aharonian, F.; Akhperjanian, A. G.; Almeida, U. Barres de; Bazer‐Bachi, A. R.; Becherini, Y.; Behera, B.; Benbow, W.; Bernlöhr, K.; Boisson, C.; Bochow, A.; Borrel, V.; Braun, I.; Brion, E.; Brucker, J.; Brun, P.; Bühler, R.; Bulik, T.; Büsching, I.; Boutelier, T.; Carrigan, S.; Chadwick, P. M.; Charbonnier, A.; Chaves, R. C. G.; Cheesebrough, A.; Chounet, L.‐M.; Clapson, A. C.; Coignet, G.; Degrange, B.; Deil, C.; Dickinson, H. J.; Djannati‐Ataï, A.; Domainko, W.; Drury, L. O'c.; Dubois, F.; Dubus, G.; Dyks, J.; Dyrda, M.; Egberts, K.; Emmanoulopoulos, D.; Espigat, P.; Farnier, C.; Feinstein, F.; Fiaßon, A.; Förster, A.; Fontaine, G.; Fusling, M.; Gabici, S.; Gallant, Y. A.; Gérard, L.; Giebels, B.; Glicenstein, J. F.; Glück, B.; Goret, P.; Hadjichristidis, C.; Hauser, D.; Hauser, M.; Heinz, Sebastian; Heinzelmann, G.; Henri, G.; Hermann, G.; Hinton, J. A.; Hoffmann, A.; Hofmann, W.; Holleran, M.; Hoppe, S.; Horns, D.; Jachołkowska, A.; Jager, O. C. de; Jung, I.; Katarzyński, K.; Kaufmann, S.; Kendziorra, E.; Kerschhaggl, M.; Khangulyan, D.; Khélifi, B.; Keogh, D.; Komin, Nu.; Kosack, K.; Lamanna, G.; Lenain, J.‐P.; Löhse, T.; Marandon, V.; Martin, Jean‐Michel; Martineau‐Huynh, O.; Marcowith, A.; Maurin, D.; McComb, T. J. L.; Medina, M. C.; Moderski, R.; Moulin, Emmanuel; Naumann-Godó, M.; Naurois, M. de; Nedbal, D.; Nekrassov, D.; Niemiec, J.; Nolan, S. J.; Ohm, S.; Olive, J.‐F.; Wilhelmi, E. de Oña; Orford, K. J.; Osborne, J. L.; Ostrowski, M.; Panter, M.; Pedaletti, G.; Pelletier, G.; Petrucci, P.-O.; Pita, S.; Pühlhofer, G.; Punch, M.; Quirrenbach, A.; Raubenheimer, Britt; Raue, M.; Rayner, S. M.; Renaud, M.; Rieger, F.; Ripken, J.; Rob, L.; Rosier‐Lees, S.; Rowell, G.; Rudak, B.; Rulten, C. B.; Ruppel, J.; Sahakian, V.; Santangelo, A.; Schlickeiser, R.; Schöck, F. M.; Schröder, R.; Schwanke, U.; Schwarzburg, S.; Schwemmer, S.; Shalchi, A.; Skilton, J. L.; Sol, H.; Spangler, D.; Stawarz, Ł.; Steenkamp, R.; Stegmann, C.; Superina, G.; Tam, P. H. T.; Tavernet, J.‐P.; Terrier, R.; Tibolla, O.; Eldik, C. van; Vasileiadis, G.; Venter, C.; Vialle, J. P.; Vincent, P.; Vivier, M.; Völk, H. J.; Volpe, F.; Wagner, S. J.; Ward, M. J.; Zdziarski, A. A.; Zech, A.

doi:10.1051/0004-6361:200810912

Cited by 28 publications

(22 citation statements)

References 32 publications

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“…This overestimation would not be conflicting if the flux of J1745-290 corresponded to flare episodes coincident with those measured at Xrays energies from SgrA*. However, as mentioned in the introduction, variability, flaring, or QPOs have not been found in the flux of the source J1745-290 (Aharonian et al 2008(Aharonian et al , 2009 . In contrast, the emission profile of the model m 12 obtained with CRs injected with the power-law index κ = 1.8 and cut-off energy cut = 0.5 PeV produces a flux within the RIAF of SgrA* that matches the upper limits detected by H.E.S.S.…”

Section: Vhe Fluxes From the Riaf Of Sgra*mentioning

confidence: 91%

“…No variability in the flux of J1745-290 was found during the simultaneous H.E.S.S. and Chandra observations performed in July 2005, when the X-ray flux of SgrA* increased by a factor of ∼ 9 (Aharonian et al 2008). A subsequent analysis with increased statistics of data and improved analysis methods displayed no variability, flaring, or quasi-periodic oscillations in the flux of J1745-290 (Aharonian et al 2009), and more recently, a monitoring campaign of SgrA* with the MAGIC telescopes reported no significant variability of the emission from this source (Ahnen et al 2017).…”

Section: Introductionmentioning

confidence: 93%

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Very-high-energy Emission from Magnetic Reconnection in the Radiative-inefficient Accretion Flow of SgrA*

Rodríguez-Ramírez

Pino

Batista

2019

ApJ

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The cosmic-ray (CR) accelerator at the galactic centre (GC) is not yet established by current observations. Here we investigate the radiative-inefficient accretion flow (RIAF) of Sagittarius A* (SgrA*) as a CR accelerator assuming acceleration by turbulent magnetic reconnection, and derive possible emission fluxes of CRs interacting within the RIAF (the central ∼ 10 13 cm). The target environment of the RIAF is modelled with numerical, general relativistic magneto-hydrodynamics (GRMHD) together with leptonic radiative transfer simulations. The acceleration of the CRs is not computed here. Instead, we inject CRs constrained by the magnetic reconnection power of the accretion flow and compute the emission/absorption of γ-rays due to these CRs interacting with the RIAF, through Monte Carlo simulations employing the CRPropa 3 code. The resulting very-high-energy (VHE) fluxes are not expected to reproduce the point source HESS J1745-290 as the emission of this source is most likely produced at pc scales. The emission profiles derived here intend to trace the VHE signatures of the RIAF as a CR accelerator and provide predictions for observations of the GC with improved angular resolution and differential flux sensitivity as those of the forthcoming Cherenkov Telescope Array (CTA). Within the scenario presented here, we find that for mass accretion rates 10 −7 M yr −1 , the RIAF of SgrA* produces VHE fluxes which are consistent with the H.E.S.S. upper limits for the GC and potentially observable by the future CTA. The associated neutrino fluxes are negligible compared with the diffuse neutrino emission measured by the IceCube.

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Section: Vhe Fluxes From the Riaf Of Sgra*mentioning

confidence: 91%

Section: Introductionmentioning

confidence: 93%

Very-high-energy Emission from Magnetic Reconnection in the Radiative-inefficient Accretion Flow of SgrA*

Rodríguez-Ramírez

Pino

Batista

2019

ApJ

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“…Sgr A ⋆ is usually in a quiescent state, and occasionally interrupted by rapid flares (on timescales ∼ 1 hr), most significantly in X-ray (Baganoff et al 2001) and near-infrared (NIR; Genzel et al 2003;Ghez et al 2004). Many such flares have been observed in various wavebands, including those detected by Chandra (Baganoff et al 2001;Eckart et al 2004Eckart et al , 2006bAharonian et al 2008;Eckart et al 2008a;Marrone et al 2008;Yusef-Zadeh et al 2008;Eckart et al 2012;Nowak et al 2012;Neilsen et al 2013;Ponti et al 2015;Yuan & Wang 2016), XMM-Newton (Goldwurm et al 2003;Porquet et al 2003Porquet et al , 2005 Yusef-Zadeh et al 2009;Trap et al 2011;Ponti et al 2015), Swift (Degenaar et al 2013(Degenaar et al , 2015, and NuSTAR (Barrière et al 2014;Dibi et al 2014). Many have also been detected in NIR (Genzel et al 2003;Eckart et al 2004Eckart et al , 2006bGhez et al 2004;Yusef-Zadeh et al 2006a;Eckart et al 2008a;Yusef-Zadeh et al 2008Kunneriath et al 2010;Trap et al 2011;Eckart et al 2012;Haubois et al 2012;Hora et al 2014;Shahzamanian et al 2015), in sub-millimeter (Eckart et al ...…”

Section: Introductionmentioning

confidence: 99%

A magnetohydrodynamic model for multiwavelength flares from Sagittarius A⋆ (I): model and the near-infrared and X-ray flares

Yuan

Wang

2017

Monthly Notices of the Royal Astronomical Society

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Flares from the supermassive black hole in our Galaxy, Sagittarius A ⋆ (Sgr A ⋆ ), are routinely observed over the last decade or so. Despite numerous observational and theoretical efforts, the nature of such flares still remains poorly understood, although a few phenomenological scenarios have been proposed. In this work, we develop the Yuan et al. (2009) scenario into a magnetohydrodynamic (MHD) model for Sgr A ⋆ flares. This model is analogous with the theory of solar flares and coronal mass ejection in solar physics. In the model, magnetic field loops emerge from the accretion flow onto Sgr A ⋆ and are twisted to form flux ropes because of shear and turbulence. The magnetic energy is also accumulated in this process until a threshold is reached. This then results in a catastrophic evolution of a flux rope with the help of magnetic reconnection in the current sheet. In this catastrophic process, the magnetic energy is partially converted into the energy of non-thermal electrons. We have quantitatively calculated the dynamical evolution of the height, size, and velocity of the flux rope, as well as the magnetic field in the flare regions, and the energy distribution of relativistic electrons in this process. We further calculate the synchrotron radiation from these electrons and compare the obtained light curves with the observed ones. We find that the model can reasonably explain the main observations of near-infrared (NIR) and X-ray flares including their light curves and spectra. It can also potentially explain the frequency-dependent time delay seen in radio flare light curves.

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“…Most notably, a simultaneous observation with H.E.S.S. and Chandra found that an X-ray outburst observed in 2007 was not correlated with any change in the γ -ray emission (Aharonian et al 2008). This implies that the source of the γ -ray emission may be distinct from the source of low-energy photons.…”

Section: Introductionmentioning

confidence: 99%

EXPLORING THE NATURE OF THE GALACTIC CENTER Γ-Ray SOURCE WITH THE CHERENKOV TELESCOPE ARRAY

Linden

Profumo

2012

ApJ

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Observations from multiple γ -ray telescopes have uncovered a high-energy γ -ray source spatially coincident with the Galactic center. Recently, a compelling model for the broadband γ -ray emission has been formulated, which posits that high-energy protons emanating from Sgr A* could produce γ -rays through π 0 decays resulting from inelastic collisions with the traversed interstellar gas in the region. Models of the gas distribution in the Galactic center region imply that the resulting γ -ray morphology would be observed as a point source with all current telescopes, but that the upcoming Cherenkov Telescope Array (CTA) may be able to detect an extended emission profile with an unmistakable morphology. Here, we critically evaluate this claim, employing a three-dimensional gas distribution model and a detailed Monte Carlo simulation, and using the anticipated effective area and angular resolution of CTA. We find that the impressive angular resolution of CTA will be key to test hadronic emission models conclusively against, for example, point source or dark matter annihilation scenarios. We comment on the relevance of this result for searches for dark matter annihilation in the Galactic center region.

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Simultaneous HESS and Chandra observations of Sagitarius A$^{\star}$ during an X-ray flare

Cited by 28 publications

References 32 publications

Very-high-energy Emission from Magnetic Reconnection in the Radiative-inefficient Accretion Flow of SgrA*

Very-high-energy Emission from Magnetic Reconnection in the Radiative-inefficient Accretion Flow of SgrA*

A magnetohydrodynamic model for multiwavelength flares from Sagittarius A⋆ (I): model and the near-infrared and X-ray flares

EXPLORING THE NATURE OF THE GALACTIC CENTER Γ-Ray SOURCE WITH THE CHERENKOV TELESCOPE ARRAY

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