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Revisiting the Westerlund 2 field with the HESS telescope array
KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.ORCID iD: 0000-0002-9769-8016
Number of Authors: 196
2011 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 525, A46- p.Article in journal (Refereed) Published
Abstract [en]

Aims. Previous observations with the HESS telescope array revealed the existence of extended very-high-energy (VHE; E > 100 GeV) gamma-ray emission, HESS J1023-575, coincident with the young stellar cluster Westerlund 2. At the time of discovery, the origin of the observed emission was not unambiguously identified, and follow-up observations have been performed to further investigate the nature of this gamma-ray source. Methods. The Carina region towards the open cluster Westerlund 2 has been re-observed, increasing the total exposure to 45.9 h. The combined dataset includes 33 h of new data and now permits a search for energy-dependent morphology and detailed spectroscopy. Results. A new, hard spectrum VHE gamma-ray source, HESS J1026-582, was discovered with a statistical significance of 7 sigma. It is positionally coincident with the Fermi LAT pulsar PSRJ1028-5819. The positional coincidence and radio/gamma-ray characteristics of the LAT pulsar favors a scenario where the TeV emission originates from a pulsar wind nebula. The nature of HESS J1023-575 is discussed in light of the deep HESS observations and recent multi-wavelength discoveries, including the Fermi LAT pulsar PSRJ1022-5746 and giant molecular clouds in the region. Despite the improved VHE dataset, a clear identification of the object responsible for the VHE emission from HESS J1023-575 is not yet possible, and contribution from the nearby high-energy pulsar and/or the open cluster remains a possibility.

Place, publisher, year, edition, pages
2011. Vol. 525, A46- p.
Keyword [en]
gamma rays: stars, HII regions
National Category
Astronomy, Astrophysics and Cosmology
URN: urn:nbn:se:kth:diva-39357DOI: 10.1051/0004-6361/201015290ISI: 000285193700095ScopusID: 2-s2.0-79951490595OAI: diva2:439772
Author count 196.Available from: 2011-09-09 Created: 2011-09-09 Last updated: 2011-09-09Bibliographically approved

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