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Multiwavelength study of the flaring activity of the supermassive black hole Sgr A* at the center of the Milky Way

Abstract : Sgr A*, the closest supermassive black hole, is an extremely low luminosity black hole emitting flares in near-infrared (NIR), X-rays and radio. The goal of this Ph.D. is to study the impact of the pericenter passage of the Dusty S-cluster Object DSO/G2 close to Sgr A* on the flaring activity. I used and improved three methods for the study in X-rays: the two-steps Bayesian blocks method to detect flares with a given false detection probability, the light curve smoothing to reduce the Poisson noise and the Monte Carlo Markov chains method for the fitting of the flare spectra. I constrained the physical parameters of the flaring region for one of the three X-ray flares detected in 2011 and for three NIR/X-ray flares detected during the 2014 Feb.-Apr. multiwavelength campaign. The X-ray and NIR activity during the 2014 Feb.-Apr. is not different from those observed before the DSO/G2 pericenter passage. I computed the intrinsic flaring rate in X-rays from Sgr A* in 1999-2015 and I detected a smaller flaring activity beginning on 2013 Oct. 28. The energy saved during this time period could explain the largest activity observed from 2014 Aug. 30 to Sept. 9.
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Emmanuelle Mossoux. Multiwavelength study of the flaring activity of the supermassive black hole Sgr A* at the center of the Milky Way. Astrophysics [astro-ph]. Université de Strasbourg, 2016. English. ⟨NNT : 2016STRAE044⟩. ⟨tel-02003539⟩

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