Discovery of extended VHE gamma -ray emission from the vicinity of the young massive stellar cluster Westerlund 1

• Published in: Astronomy and astrophysics (Berlin) Vol. 537; p. 1
• Main Authors: Abramowski, A, Acero, F, Aharonian, F, Akhperjanian, A G, Anton, G, Balzer, A, Barnacka, A, de Almeida, U Barres, Becherini, Y, Kneiske, T, Komin, Nu, Kosack, K, Kossakowski, R, Laffon, H, Lamanna, G, Lennarz, D, Lohse, T, Lopatin, A, Lu, C-C, Becker, J, Marandon, V, Marcowith, A, Masbou, J, Maurin, D, Maxted, N, Mayer, M, McComb, T J L, Medina, M C, Mehault, J, Moderski, R, Behera, B, Moulin, E, Naumann, C L, Naumann-Godo, M, de Naurois, M, Nedbal, D, Nekrassov, D, Nguyen, N, Nicholas, B, Niemiec, J, Nolan, S J, Bernlohr, K, Ohm, S, Wilhelmi, E de Ona, Opitz, B, Ostrowski, M, Oya, I, Panter, M, Arribas, M Paz, Pedaletti, G, et. al
• Format: Journal Article
• Language: English
• Published: 01.01.2012
• ISSN: 0004-6361; 1432-0746

This study aims to investigate particle acceleration processes in the vicinity of the young massive stellar cluster Westerlund 1. Imaging of Cherenkov light from gamma -ray induced particle cascades in the Earth's atmosphere is used to search for VHE gamma rays from the region around Wd 1. Possible catalogued counterparts are searched for and discussed in terms of morphology and energetics of the HESS source. The detection of the degree-scale extended VHE gamma -ray source HESS J1646-458 is reported based on 45 h of HESS observations performed between 2004 and 2008. The VHE gamma -ray source is centred on the nominal position of Wd 1 and detected with a total statistical significance of similar to 20 sigma . Four objects coincident with HESS J1646-458 are discussed in the search of a counterpart, namely the magnetar CXOU J164710.2-455216, the X-ray binary 4U 1642-45, the pulsar PSR J1648-4611 and the massive stellar cluster Wd 1. In a single-source scenario, Wd 1 is favoured as site of VHE particle acceleration.