Guillaume Belanger:

ESA: INTEGRAL


I did a B.Sc. (1991-1996) in Physics at McGill University in
Montreal, Quebec in Canada. My interests ranged from Physics and
Math to History and Philosophy, hence the extra year.

After receiving my B.Sc., I worked for half a year and then went on
a 7-month long trip where I made my way from Paris et Kathmandu
through eastern Europe and Greece to Turkey (1 month), Iran (2
weeks), Pakistan (3 weeks), India (2 months) and Nepal (2 weeks).

Upon my return to Ottawa, Canada, I worked at the Ministry of
Natural Resources in the Advanced Combustion Technology laboratory
of CANMET.  My work there involved imaging techniques for flames
and cold flows in industrial burners using the laser sheet
illumination (or LSI) technique.

In the fall of 2000 I started a M.Sc. in Particle Physics at
Carleton University in Ottawa, where beyond taking advanced
classes, I worked on the construction of the second hadronic unit
of the ATLAS Forward Calorimeter (FCal) composed of one EM unit
and two hadronic ones. This work ended with a one-month stay at
CERN for the testing of the detector. It is during this month that
I completed the last sections of my M.Sc. thesis in which I
investigated phenomenological aspects of Large Extra Dimensions and
the possible means of detecting them with ATLAS. I  defended this
thesis in September 2002.

Immediately after obtaining my M.Sc., I left for France with my
wife and 4 year-old son to start a Ph.D. in High Energy
Astrophysics. This was done at the Service d'Astrophysique (SAp)
of the CEA in Saclay near Paris. I worked closely with Andrea
Goldwurm, and Jacque Paul was my official thesis supervisor. The
research I carried out at the SAp was related to the study of the
high energy behaviour of the Galactic centre and in particular of
Sgr A*. I worked a lot with Integral data at first, and then
integrated the analysis of XMM data into my research.

With Integral, I detected for the first time emission from the
Nuclear region of the Galaxy at energies above 20 keV (Belanger et
al. 2004).  This emission was then studied in detail and we found
that it must be a compact and yet diffuse emission region centered
very close to the Galactic nucleus, Sgr A* (Belanger et al. 2006).
The nature of this  emission is still unknown and under
investigation (Revnivtsev et al. 2005, Krivonos et al. 2006,
Belanger et al. 2007 in prep).

With XMM-Newton, I found the first significant periodic (or 
semi-periodic) signal during an X-ray flare from Sgr A* detected 
simultaneously by XMM and HST on August 31, 2004. This flaring
event had a peak luminosity of 10^35 erg/s, ~40 times that of the
quiescent X-ray luminosity, and lasted a total of ~3 h. This
detection pulled me into the realm of timing analysis and its
complicated techniques, from which I have not yet emerged. The
work should be published in the coming months (Belanger et al.
2007b in prep).

This is a very interesting detection indeed, since it gives us
detailed information about the structure of the hot plasma that
rotates around the massive black hole Sgr A*. Further studies
based on this result have been carried out and proved to be very
informative (see Tagger and  Melia 2006, and Falanga et al. 2007,
just submitted).

We believe that the condition at the GC do not allow the formation
of a large accretion disk, but that occasional clumps of matter
that somehow succeed in reaching these confines, fall onto a
small, very hot and highly magnetized accretion disk that extends
to about 25 Schwartzschild radii. This leads to disturbances
(possibly initiating MHD instabilities) in the disk giving rise to
flares or eruptions very close to Sgr A*. The period of 22.2
minutes gives us the dynamic scale of the evolution of the event
around the black hole.

My research continues in this field and will be extended to the
study of energetic particle interactions with the molecular
matter concentrated in giant and dense clouds orbiting Sgr A* in
the Central Molecular Zone.