Issue |
A&A
Volume 525, January 2011
|
|
---|---|---|
Article Number | A46 | |
Number of page(s) | 8 | |
Section | Interstellar and circumstellar matter | |
DOI | https://doi.org/10.1051/0004-6361/201015290 | |
Published online | 30 November 2010 |
Revisiting the Westerlund 2 field with the HESS telescope array
1
Max-Planck-Institut für Kernphysik, PO Box 103980, 69029
Heidelberg,
Germany
e-mail: emma@mpi-hd.mpg.de
2
Yerevan Physics Institute, 2 Alikhanian Brothers St., 375036
Yerevan,
Armenia
3
Centre d’Étude Spatiale des Rayonnements, CNRS/UPS,
9 Av. du Colonel Roche,
BP 4346, 31029
Toulouse Cedex 4,
France
4
Universität Hamburg, Institut für
Experimentalphysik, Luruper Chaussee
149, 22761
Hamburg,
Germany
5
Institut für Physik, Humboldt-Universität zu Berlin,
Newtonstr. 15, 12489
Berlin,
Germany
6
LUTH, Observatoire de Paris, CNRS, Université Paris
Diderot, 5 Place Jules
Janssen, 92190
Meudon,
France
7
CEA Saclay, DSM/IRFU, 91191
Gif-Sur-Yvette Cedex,
France
8
University of Durham, Department of Physics,
South Road, Durham
DH1 3LE,
UK
9
Unit for Space Physics, North-West University,
Potchefstroom
2520, South
Africa
10
Laboratoire Leprince-Ringuet, Ecole Polytechnique,
CNRS/IN2P3, 91128
Palaiseau,
France
11
Laboratoire d’Annecy-le-Vieux de Physique des Particules,
Université de Savoie, CNRS/IN2P3, 74941
Annecy-le-Vieux,
France
12
Astroparticule et Cosmologie (APC), CNRS, Université Paris 7 Denis
Diderot, 10, rue Alice Domon et
Léonie Duquet, 75205
Paris Cedex 13,
France
UMR 7164 (CNRS, Université Paris VII, CEA, Observatoire de Paris).
13
Dublin Institute for Advanced Studies,
5 Merrion Square, Dublin 2, Ireland
14
Landessternwarte, Universität Heidelberg,
Königstuhl, 69117
Heidelberg,
Germany
15
Laboratoire de Physique Théorique et Astroparticules, Université
Montpellier 2, CNRS/IN2P3, CC 70,
Place Eugène Bataillon, 34095
Montpellier Cedex 5,
France
16
Universität Erlangen-Nürnberg, Physikalisches
Institut, Erwin-Rommel-Str.
1, 91058
Erlangen,
Germany
17
Laboratoire d’Astrophysique de Grenoble, INSU/CNRS, Université
Joseph Fourier, BP
53, 38041
Grenoble Cedex 9,
France
18
Institut für Astronomie und Astrophysik, Universität
Tübingen, Sand 1,
72076
Tübingen,
Germany
19
LPNHE, Université Pierre et Marie Curie Paris 6, Université Denis
Diderot Paris 7, CNRS/IN2P3, 4
Place Jussieu, 75252
Paris Cedex 5,
France
20 Charles University, Faculty of Mathematics and Physics, Institute of Particle and Nuclear Physics, V Holešovičkách 2, 180 00 Prague 8, Czech Republic
21
Institut für Theoretische Physik, Lehrstuhl IV: Weltraum und
Astrophysik, Ruhr-Universität Bochum, 44780 Bochum, Germany
22
University of Namibia, Department of Physics,
Private Bag 13301, Windhoek, Namibia
23
Obserwatorium Astronomiczne, Uniwersytet Jagielloński,
ul. Orla
171, 30-244
Kraków,
Poland
24
Nicolaus Copernicus Astronomical Center,
ul. Bartycka 18, 00-716
Warsaw,
Poland
25
School of Physics & Astronomy, University of
Leeds, Leeds
LS2 9JT,
UK
26
School of Chemistry & Physics, University of
Adelaide, Adelaide
5005,
Australia
27
Toruń Centre for Astronomy, Nicolaus Copernicus
University, ul. Gagarina
11, 87-100
Toruń,
Poland
28
Instytut FizykiJa¸drowej PAN, ul. Radzikowskiego 152, 31-342
Kraków,
Poland
29
Astronomical Observatory, The University of Warsaw,
Al. Ujazdowskie 4, 00-478
Warsaw,
Poland
30
Institut für Astro- und Teilchenphysik,
Leopold-Franzens-Universität Innsbruck, 6020
Innsbruck,
Austria
31
Oskar Klein Centre, Department of Physics, Stockholm University,
Albanova University Center, 10691
Stockholm,
Sweden
32
Oskar Klein Centre, Department of Physics, Royal Institute of
Technology (KTH), Albanova, 10691
Stockholm,
Sweden
33
Department of Physics and Astronomy, The University of Leicester,
University Road, Leicester, LE1
7RH, UK
35
National Academy of Sciences of the Republic of Armenia, Yerevan
36
Department of Astrophysics, Nagoya University,
Furocho, Chikusaku,
Nagoya
464-8602,
Japan
Received:
28
June
2010
Accepted:
9
September
2010
Aims. Previous observations with the HESS telescope array revealed the existence of extended very-high-energy (VHE; E > 100 GeV) γ-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 γ-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 γ-ray source, HESS J1026–582, was discovered with a statistical significance of 7σ. It is positionally coincident with the Fermi LAT pulsar PSR J1028–5819. The positional coincidence and radio/γ-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 PSR J1022–5746 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.
Key words: gamma rays: stars / HII regions
© ESO, 2010
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