Untitled - Laboratoire d'Astrophysique de l'Observatoire de Grenoble

Chapter 15
Results
15.1 History and group composition
In the eigthies, the study of non-thermal phenomena in AGNs was the main research activity of Guy Pelletier,
who came from the plasma physics community. This was essentially the only theoretical work in the laboratory
(Dir. Alain Omont) which, at that time, was originally oriented towards Radio-Astronomy with a focus on the
interstellar medium. This AGN activity then gave birth to a group in the early nineties when Gilles Henri,
coming from the University of Paris XI got a permanent position at the University of Grenoble and when
two brilliant students, Françoise Rosso and Jonathan Ferreira, were hired for a thesis program on Astrophysical
Magnetohydrodynamics (MHD) with G. Pelletier. We thus started a larger activity devoted to accretion-ejection
for both AGNs and Young Stellar Objects (hereafter YSOs) with the students and a new activity devoted to
the High Energy aspect of AGNs with Gilles Henri (the first gamma spectra of some AGNs were about to be
produced by EGRET).
The laboratory was about to increase dramatically with the opening of Infra Red activity and the coming of
a group involved on Young Stellar Objects was under discussion. We were particularly in favor of welcoming this
new component because this was about to open a new field of collaboration in the laboratory and we warmly
supported the arrival of Claude Bertout and his team. Then the laboratory was metamorphosed and our group,
which hired new permanent researchers from Toulouse (Pierre-Yves Longaretti and Didier Fraix-Burnet), took
the name SHERPA (Sources of High Energy Relativistic Plasmas Accretion-ejection). It emphasizes both the
type of objects we deal with, namely sources of high energy powered by accretion-ejection, and the type of
physics we develop, namely, MHD, relativistic plasma physics and transfer of high energy radiation.
Table 1 lists the current permanent staff with their main activity. In 2005, the group hosts Yaël Fuchs
with an ATER position (one year) and three graduate students: Clément Cabanac (started in 2003), Geoffroy
Lesur (started in 2004) and Nicolas Bessolaz (started in 2004, in co-direction with the FOST team). In Fall
2005 a post-doc, Claudio Zanni, will join the group for 2 or 3 years, as well as another PhD student Timothée
Boutelier.
15.2 Specific approach
Among the teams working on MHD astrophysics, high energy cosmic phenomena and the environment of compact
objects, we adopted the following attitude. Instead of running after scoops, we firmly decided to develop
ground researches about the physical issues and the interrelations between the gross phenomena governed by
gravitation and MHD, the kinetic level of relativistic plasmas, including the physics of particle acceleration, and
the physics of the high energy photon emission. Therefore, we are mostly involved in theoretical developments
together with numerical simulations. However, we also provide our expertise by participating in large collaborations
organized for the ”exploitation” of facilities in the whole energy range from millimeter to TeV gamma
range.
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