Séminaires du
Département d'Astrophysique, Géophysique et Océanographie

Jeudi 30 mars, 15h45

Salle de réunion AGO (local -1/14)
Institut d'Astrophysique et de Géophysique
Quartier Agora, Allée du 6 Août, 19C, B-4000 Liège 1 (Sart-Tilman)

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

Enmanuelle Mossoux
(STAR Institute)

Sgr A* is the closest supermassive black hole, located at the center of our Galaxy at only 8kpc from the Earth. is an extremely low luminosity black hole experiencing several increases of flux (named flares) in near-infrared (NIR), X-rays and radio. On 2011, the DSO/G2 object was detected on its way towards Sgr A*. The goal of my Ph.D. thesis was to study the impact of the pericenter passage of the DSO/G2 close to Sgr A* on the flaring activity.

I first analyzed the 2011 X-ray campaign for the study of Sgr A* to constrain the physical parameters of the flaring region. I then studied the large multiwavelength campaign of 2014 Feb.­-Apr. which includes observations in radio, NIR and X-rays. Thanks to the NIR observations of this campaign, we were able to conclude that the DSO/G2 is a pre­-main sequence star of 1-­2 solar masses emitting by magnetospheric accretion. We observed it after its pericenter passage which occurred on 2014 Apr. 20 which allowed us to conclude that it survived to the tidal forces and that the flaring activity of Sgr A* observed during this campaign is not different from those observed before the DSO/G2 pericenter passage.

I finally reprocessed the X-ray observations of Sgr A* from 1999 to 2015 obtained with XMM-Newton, Chandra and Swift to study the overall X-ray flaring activity. I detected 107 flares during these observations. I computed the detection efficiency of each instrument to compute the intrinsic flaring rate by correcting from the detection bias. I detected a smaller flaring activity for the less energetic flares which occurring between 2013 July 27 and Oct. 28 and a larger flaring activity for the more energetic flares occurring on 2014 Aug. 31. This change of flaring rate can be explained by the energy balance between the decay and the increase of the X-ray flaring rate. The DSO/G2 pericenter passage is thus not needed to explain the change of flaring rate from Sgr A*.

Café, thé et biscuits seront servis après le séminaire...