Detection of extended very-high-energy γ-ray emission towards the young stellar cluster Westerlund 2

被引：109

作者：

Aharonian, F.

Akhperjanian, A. G.

Bazer-Bachi, A. R.

Beilicke, M.

Benbow, W.

Berge, D.

Bernloehr, K.

Boisson, C.

Bolz, O.

Borrel, V.

Braun, I.

Brion, E.

Brown, A. M.

Buehler, R.

Buesching, I.

Boutelier, T.

Carrigan, S.

Chadwick, P. M.

Chounet, L.-M.

Coignet, G.

Cornils, R.

Costamante, L.

Degrange, B.

Dickinson, H. J.

Djannati-Atai, A.

Drury, L. O'C.

Dubus, G.

Egberts, K.

Emmanoulopoulos, D.

Espigat, P.

Farnier, C.

Feinstein, F.

Ferrero, E.

Fiasson, A.

Fontaine, G.

Funk, Seb.

Funk, S.

Fuessling, M.

Gallant, Y. A.

Giebels, B.

Glicenstein, J. F.

Glueck, B.

Goret, P.

Hadjichristidis, C.

Hauser, D.

Heinzelmann, G.

Henri, G.

Hermann, G.

Hinton, J. A.

Hoffmann, A.

机构：

[1] Max Planck Inst Kernphys, D-69029 Heidelberg, Germany

[2] Yerevan Phys Inst, Yerevan 375036, Armenia

[3] UPS, CNRS, Ctr Etud Spatiale Rayonnements, F-31029 Toulouse 4, France

[4] Univ Hamburg, Inst Expt Phys, D-22761 Hamburg, Germany

[5] Humboldt Univ, Inst Phys, D-12489 Berlin, Germany

[6] Observ Paris, CNRS, UMR 8102, LUTH,Sect Meudon, F-92195 Meudon, France

[7] Ctr Etud Saclay, DAPNIA, DSM, CEA, F-91191 Gif Sur Yvette, France

[8] Univ Durham, Dept Phys, Durham DH1 3LE, England

[9] NW Univ, Unit Space Phys, ZA-2520 Potchefstroom, South Africa

[10] Ecole Polytech, CNRS, IN2P3, Lab Leprince Ringuet, F-91128 Palaiseau, France

[11] CNRS, IN2P3, Lab Annecy le Vieux Phys Particules, F-74941 Annecy Le Vieux, France

[12] APC, F-75231 Paris 05, France

[13] Univ Paris 07, CEA, Observ Paris, CNRS,UMR 7164, F-75221 Paris 05, France

[14] Dublin Inst Adv Studies, Dublin 2, Ireland

[15] Univ Heidelberg, D-69117 Heidelberg, Germany

[16] Univ Montpellier 2, CNRS, IN2P3, Lab Phys Theor & Astroparticules, F-34095 Montpellier 5, France

[17] Univ Erlangen Nurnberg, Inst Phys, D-91058 Erlangen, Germany

[18] Univ Grenoble 1, CNRS, INSU, Lab Astrophys Grenoble, F-38041 Grenoble 9, France

[19] Univ Tubingen, Inst Astron & Astrophys, D-72076 Tubingen, Germany

[20] Univ Paris 06, CNRS, IN2P3, Lab Phys Nucl & Hautes Energies, F-75252 Paris 5, France

[21] Univ Paris 07, CNRS, IN2P3, Lab Phys Nucl & Hautes Energies, F-75252 Paris 5, France

[22] Charles Univ Prague, Inst Nucl & Particle Phys, CR-18000 Prague 8, Czech Republic

[23] Ruhr Univ Bochum, Inst Theoret Phys, Lehrstuhl Weltraum & Astrophys 4, D-44780 Bochum, Germany

[24] Univ Namibia, Windhoek, Namibia

来源：

ASTRONOMY & ASTROPHYSICS | 2007年 / 467卷 / 03期

关键词：

ISM : individual objects : HESS J1023-575; ISM : individual objects : RCW 49 (NGC 3247; G284.3-0.3); stars : Wolf-Rayet; stars : individual : WR 20a; gamma rays : observations; ISM : HII regions;

D O I：

10.1051/0004-6361:20066950

中图分类号：

P1 [天文学];

学科分类号：

0704 ;

摘要：

Aims. Results from gamma-ray observations by the HESS telescope array in the direction of the young stellar cluster Westerlund 2 are presented. Methods. Stereoscopic imaging of Cherenkov light emission of gamma-ray induced showers in the atmosphere is used to study the celestial region around the massive Wolf-Rayet (WR) binary WR 20a. Spectral and positional analysis is performed using standard event reconstruction techniques and parameter cuts. Results. The detection of a new gamma-ray source is reported from HESS observations in 2006. HESS J1023 - 575 is found to be coincident with the young stellar cluster Westerlund 2 in the well-known HII complex RCW49. The source is detected with a statistical significance of more than 9 sigma, and shows extension beyond a point-like object within the HESS point-spread function. The differential gamma-ray spectrum of the emission region is measured over approximately two orders of magnitude in flux. Conclusions. The spatial coincidence between HESS J1023 - 575 and the young open cluster Westerlund 2, hosting e. g. the massive WR binary WR 20a, requires one to look into a variety of potential models to account for the observed very-high-energy (VHE) gamma-ray emission. Considered emission scenarios include emission from the colliding wind zone of WR 20a, collective stellar winds from the extraordinary ensemble of hot and massive stars in the stellar cluster Westerlund 2, diffusive shock acceleration in the wind-blown bubble itself, and supersonic winds breaking out into the interstellar medium ( ISM). The observed source extension argues against a single star origin of the observed VHE emission.

引用

页码：1075 / 1080

页数：6

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