München 2009 – scientific programme

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T: Fachverband Teilchenphysik

T 86: Gamma-Astronomie 5

T 86.4: Talk

Thursday, March 12, 2009, 17:30–17:45, M218

H.E.S.S. observations towards the massive star cluster Westerlund 1 — •Stefan Ohm¹, Emma de Ona Wilhelmi², Milton Virgilio Fernandes³, and Dieter Horns³ — ¹Max-Planck-Institut für Kernphysik, Heidelberg — ²APC, Paris — ³Institut für Experimentalphysik, Universitaet Hamburg

Westerlund 1 is known as the most massive star cluster in our galaxy, harboring the richest population (≥ 26) of stars in the Wolf-Rayet (WR) phase. The dissipated power in the form of kinetic energy in stellar winds and expanding supernova (SN) shells reaches L_SN≈ 3× 10³⁹ ergs s⁻¹ in this system. At least some part of the kinetic energy is available to accelerate particles to very high energies, e.g. at the boundaries of wind-blown bubbles, in colliding wind zones in binary systems or in the framework of collective wind or wind/SN ejecta scenarios. These acceleration mechanisms and the detection of the young stellar cluster Westerlund 2 in very-high-energy (VHE) gamma-rays suggest Westerlund 1 as the foremost promising target in that category for VHE emission. Here we present results of H.E.S.S. observations of Westerlund 1 performed from 2004 to 2008.