Please use this identifier to cite or link to this item: http://hdl.handle.net/2440/71351
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dc.contributor.authorMaxted, N.en
dc.contributor.authorNicholas, B.en
dc.contributor.authorRowell, G.en
dc.date.issued2012en
dc.identifier.citationAstronomy and Astrophysics, 2012; 537:A114-1-A114-11en
dc.identifier.issn0004-6361en
dc.identifier.issn1432-0746en
dc.identifier.urihttp://hdl.handle.net/2440/71351-
dc.description.abstractAims. Results obtained in very-high-energy (VHE; E ≥ 100 GeV) γ-ray observations performed with the H.E.S.S. telescope array are used to investigate particle acceleration processes in the vicinity of the young massive stellar cluster Westerlund 1 (Wd 1). Methods. Imaging of Cherenkov light from γ-ray induced particle cascades in the Earth’s atmosphere is used to search for VHE γ rays from the region around Wd 1. Possible catalogued counterparts are searched for and discussed in terms of morphology and energetics of the H.E.S.S. source. Results. The detection of the degree-scale extended VHE γ-ray source HESS J1646–458 is reported based on 45 h of H.E.S.S. observations performed between 2004 and 2008. The VHE γ-ray source is centred on the nominal position of Wd 1 and detected with a total statistical significance of ~20σ. The emission region clearly extends beyond the H.E.S.S. point-spread function (PSF). The differential energy spectrum follows a power law in energy with an index of Γ = 2.19 ± 0.08stat ± 0.20sys and a flux normalisation at 1 TeV of Φ0 = (9.0 ± 1.4stat ± 1.8sys) × 10⁻¹²   TeV⁻¹ cm⁻²  s⁻¹. The integral flux above 0.2 TeV amounts to (5.2 ± 0.9) × 10⁻¹¹   cm⁻²   s⁻¹. Conclusions. 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. Here, a hadronic parent population would be accelerated within the stellar cluster. Beside this, there is evidence for a multi-source origin, where a scenario involving PSR J1648–4611 could be viable to explain parts of the VHE γ-ray emission of HESS J1646–458.en
dc.description.statementofresponsibilityH.E.S.S. Collaboration: A. Abramowski ... N. Maxted ... B. Nicholas ... G. Rowell ... et al.en
dc.language.isoenen
dc.publisherEDP Sciencesen
dc.rights© ESO 2012en
dc.subjectopen clusters and associations: general; gamma rays: stars; astroparticle physicsen
dc.titleDiscovery of extended VHE γ-ray emission from the vicinity of the young massive stellar cluster Westerlund 1en
dc.title.alternativeDiscovery of extended VHE gamma-ray emission from the vicinity of the young massive stellar cluster Westerlund 1en
dc.typeJournal articleen
dc.identifier.rmid0020117318en
dc.identifier.doi10.1051/0004-6361/201117928en
dc.identifier.pubid25497-
pubs.library.collectionIPAS publicationsen
pubs.verification-statusVerifieden
pubs.publication-statusPublisheden
dc.identifier.orcidRowell, G. [0000-0002-9516-1581]en
Appears in Collections:IPAS publications

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