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

F. Aharonian; A. G. Akhperjanian; A. R. Bazer-Bachi; M. Beilicke; W. Benbow; D. Berge; K. Bernlöhr; C. Boisson; O. Bolz; V. Borrel; I. Braun; E. Brion; A. M. Brown; R. Bühler; I. Büsching; T. Boutelier; S. Carrigan; P. M. Chadwick; L. M. Chounet; G. Coignet; R. Cornils; L. Costamante; B. Degrange; H. J. Dickinson; A. Djannati-Ataï; L. O'C Drury; G. Dubus; K. Egberts; D. Emmanoulopoulos; P. Espigat; C. Farnier; F. Feinstein; E. Ferrero; A. Fiasson; G. Fontaine; Seb Funk; S. Funk; M. Füßling; Y. A. Gallant; B. Giebels; J. F. Glicenstein; B. Glück; P. Goret; C. Hadjichristidis; D. Hauser; M. Hauser; G. Heinzelmann; G. Henri; G. Hermann; J. A. Hinton; A. Hoffmann; W. Hofmann; M. Holleran; S. Hoppe; D. Horns; A. Jacholkowska; O. C. De Jager; E. Kendziorra; M. Kerschhaggl; B. Khélifi; Nu Komin; K. Kosack; G. Lamanna; J. Latham; R. Le Gallou; A. Lemière; M. Lemoine-Goumard; T. Lohse; J. M. Martin; O. Martineau-Huynh; A. Marcowith; C. Masterson; G. Maurin; T. J.L. McComb; E. Moulin; M. De Naurois; D. Nedbal; S. J. Nolan; A. Noutsos; J. P. Olive; K. J. Orford; J. L. Osborne; M. Panter; G. Pelletier; P. O. Petrucci; S. Pita; G. Pühlhofer; M. Punch; S. Ranchon; B. C. Raubenheimer; M. Raue; S. M. Rayner; A. Reimer; O. Reimer; J. Ripken; L. Rob; L. Rolland; S. Rosier-Lees; G. Rowell; V. Sahakian; A. Santangelo; L. Sauge; S. Schlenker; R. Schlickeiser; R. Schröder; U. Schwanke; S. Schwarzburg; S. Schwemmer; A. Shalchi; H. Sol; D. Spangler; F. Spanier; R. Steenkamp; C. Stegmann; G. Superina; P. H. Tam; J. P. Tavernet; R. Terrier; M. Tluczykont; C. Van Eldik; G. Vasileiadis; C. Venter; J. P. Vialle; P. Vincent; H. J. Volk; S. J. Wagner; M. Ward

doi:10.1051/0004-6361:20066950

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

F. Aharonian
, A. G. Akhperjanian
, A. R. Bazer-Bachi
, M. Beilicke
, W. Benbow
, D. Berge
, K. Bernlöhr
, C. Boisson
, O. Bolz
, V. Borrel
, I. Braun
, E. Brion
, A. M. Brown
, R. Bühler
, I. Büsching
, T. Boutelier
, S. Carrigan
, P. M. Chadwick
, L. M. Chounet
, G. Coignet

R. Cornils, L. Costamante, B. Degrange, H. J. Dickinson, A. Djannati-Ataï, L. O'C Drury, G. Dubus, K. Egberts, D. Emmanoulopoulos, P. Espigat, C. Farnier, F. Feinstein, E. Ferrero, A. Fiasson, G. Fontaine, Seb Funk, S. Funk, M. Füßling, Y. A. Gallant, B. Giebels, J. F. Glicenstein, B. Glück, P. Goret, C. Hadjichristidis, D. Hauser, M. Hauser, G. Heinzelmann, G. Henri, G. Hermann, J. A. Hinton, A. Hoffmann, W. Hofmann, M. Holleran, S. Hoppe, D. Horns, A. Jacholkowska, O. C. De Jager, E. Kendziorra, M. Kerschhaggl, B. Khélifi, Nu Komin, K. Kosack, G. Lamanna, J. Latham, R. Le Gallou, A. Lemière, M. Lemoine-Goumard, T. Lohse, J. M. Martin, O. Martineau-Huynh, A. Marcowith, C. Masterson, G. Maurin, T. J.L. McComb, E. Moulin, M. De Naurois, D. Nedbal, S. J. Nolan, A. Noutsos, J. P. Olive, K. J. Orford, J. L. Osborne, M. Panter, G. Pelletier, P. O. Petrucci, S. Pita, G. Pühlhofer, M. Punch, S. Ranchon, B. C. Raubenheimer, M. Raue, S. M. Rayner, A. Reimer, O. Reimer, J. Ripken, L. Rob, L. Rolland, S. Rosier-Lees, G. Rowell, V. Sahakian, A. Santangelo, L. Sauge, S. Schlenker, R. Schlickeiser, R. Schröder, U. Schwanke, S. Schwarzburg, S. Schwemmer, A. Shalchi, H. Sol, D. Spangler, F. Spanier, R. Steenkamp, C. Stegmann, G. Superina, P. H. Tam, J. P. Tavernet, R. Terrier, M. Tluczykont, C. Van Eldik, G. Vasileiadis, C. Venter, J. P. Vialle, P. Vincent, H. J. Volk, S. J. Wagner, M. Ward

Max-Planck-Institut für Kernphysik
Yerevan Physics Institute
Centre national de la recherche scientifique
Universität Hamburg
European Organization for Nuclear Research
Humboldt-Universität zu Berlin
Institut Pierre Simon Laplace, CNRS and CEA
Durham University
North-West University
Ip Paris
Université Paris-Sud
European Associated Laboratory for Gamma-Ray Astronomy
Astroparticule and Cosmol APC
Dublin Institute for Advanced Studies
Landessternwarte Heidelberg
Laboratoire Univers et Particules de Montpellier
Friedrich-Alexander University (FAU) Erlangen-Nürnberg and Universitätsklinikum Erlangen
University of Leeds
University of Tübingen
Universités Paris VI and VII
Charles University
Stanford University
University of Adelaide
Ruhr-University Bochum
University of Namibia
c/o DESY

Research output: Contribution to journal › Article › peer-review

Abstract

Aims. Results from γ-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 γ-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 γ-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 RCW 49. The source is detected with a statistical significance of more than 9σ, and shows extension beyond a point-like object within the HESS point-spread function. The differential γ-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) γ-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.

Original language	English
Pages (from-to)	1075-1080
Number of pages	6
Journal	Astronomy and Astrophysics
Volume	467
Issue number	3
DOIs	https://doi.org/10.1051/0004-6361:20066950
Publication status	Published - 1 Jan 2007
Externally published	Yes

Keywords

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

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10.1051/0004-6361:20066950

Cite this

Aharonian, F., Akhperjanian, A. G., Bazer-Bachi, A. R., Beilicke, M., Benbow, W., Berge, D., Bernlöhr, K., Boisson, C., Bolz, O., Borrel, V., Braun, I., Brion, E., Brown, A. M., Bühler, R., Büsching, I., Boutelier, T., Carrigan, S., Chadwick, P. M., Chounet, L. M., ... Ward, M. (2007). Detection of extended very-high-energy γ-ray emission towards the young stellar cluster Westerlund 2. Astronomy and Astrophysics, 467(3), 1075-1080. https://doi.org/10.1051/0004-6361:20066950

@article{153f713d3128482bb562a23c0cb552e8,

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

abstract = "Aims. Results from γ-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 γ-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 γ-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 RCW 49. The source is detected with a statistical significance of more than 9σ, and shows extension beyond a point-like object within the HESS point-spread function. The differential γ-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) γ-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.",

keywords = "Gamma rays: observations, ISM: HII regions, ISM: individual objects: HESS J1023-575, ISM: individual objects: RCW 49 (NGC 3247, G284.3-0.3), Stars: Wolf-Rayet, Stars: individual: WR 20a",

author = "F. Aharonian and Akhperjanian, \{A. G.\} and Bazer-Bachi, \{A. R.\} and M. Beilicke and W. Benbow and D. Berge and K. Bernl{\"o}hr and C. Boisson and O. Bolz and V. Borrel and I. Braun and E. Brion and Brown, \{A. M.\} and R. B{\"u}hler and I. B{\"u}sching and T. Boutelier and S. Carrigan and Chadwick, \{P. M.\} and Chounet, \{L. M.\} and G. Coignet and R. Cornils and L. Costamante and B. Degrange and Dickinson, \{H. J.\} and A. Djannati-Ata{\"i} and \{O'C Drury\}, L. and G. Dubus and K. Egberts and D. Emmanoulopoulos and P. Espigat and C. Farnier and F. Feinstein and E. Ferrero and A. Fiasson and G. Fontaine and Seb Funk and S. Funk and M. F{\"u}{\ss}ling and Gallant, \{Y. A.\} and B. Giebels and Glicenstein, \{J. F.\} and B. Gl{\"u}ck and P. Goret and C. Hadjichristidis and D. Hauser and M. Hauser and G. Heinzelmann and G. Henri and G. Hermann and Hinton, \{J. A.\} and A. Hoffmann and W. Hofmann and M. Holleran and S. Hoppe and D. Horns and A. Jacholkowska and \{De Jager\}, \{O. C.\} and E. Kendziorra and M. Kerschhaggl and B. Kh{\'e}lifi and Nu Komin and K. Kosack and G. Lamanna and J. Latham and \{Le Gallou\}, R. and A. Lemi{\`e}re and M. Lemoine-Goumard and T. Lohse and Martin, \{J. M.\} and O. Martineau-Huynh and A. Marcowith and C. Masterson and G. Maurin and McComb, \{T. J.L.\} and E. Moulin and \{De Naurois\}, M. and D. Nedbal and Nolan, \{S. J.\} and A. Noutsos and Olive, \{J. P.\} and Orford, \{K. J.\} and Osborne, \{J. L.\} and M. Panter and G. Pelletier and Petrucci, \{P. O.\} and S. Pita and G. P{\"u}hlhofer and M. Punch and S. Ranchon and Raubenheimer, \{B. C.\} and M. Raue and Rayner, \{S. M.\} and A. Reimer and O. Reimer and J. Ripken and L. Rob and L. Rolland and S. Rosier-Lees and G. Rowell and V. Sahakian and A. Santangelo and L. Sauge and S. Schlenker and R. Schlickeiser and R. Schr{\"o}der and U. Schwanke and S. Schwarzburg and S. Schwemmer and A. Shalchi and H. Sol and D. Spangler and F. Spanier and R. Steenkamp and C. Stegmann and G. Superina and Tam, \{P. H.\} and Tavernet, \{J. P.\} and R. Terrier and M. Tluczykont and \{Van Eldik\}, C. and G. Vasileiadis and C. Venter and Vialle, \{J. P.\} and P. Vincent and Volk, \{H. J.\} and Wagner, \{S. J.\} and M. Ward",

year = "2007",

month = jan,

day = "1",

doi = "10.1051/0004-6361:20066950",

language = "English",

volume = "467",

pages = "1075--1080",

journal = "Astronomy and Astrophysics",

issn = "0004-6361",

number = "3",

}

Aharonian, F, Akhperjanian, AG, Bazer-Bachi, AR, Beilicke, M, Benbow, W, Berge, D, Bernlöhr, K, Boisson, C, Bolz, O, Borrel, V, Braun, I, Brion, E, Brown, AM, Bühler, R, Büsching, I, Boutelier, T, Carrigan, S, Chadwick, PM, Chounet, LM, Coignet, G, Cornils, R, Costamante, L, Degrange, B, Dickinson, HJ, Djannati-Ataï, A, O'C Drury, L, Dubus, G, Egberts, K, Emmanoulopoulos, D, Espigat, P, Farnier, C, Feinstein, F, Ferrero, E, Fiasson, A, Fontaine, G, Funk, S, Funk, S, Füßling, M, Gallant, YA, Giebels, B, Glicenstein, JF, Glück, B, Goret, P, Hadjichristidis, C, Hauser, D, Hauser, M, Heinzelmann, G, Henri, G, Hermann, G, Hinton, JA, Hoffmann, A, Hofmann, W, Holleran, M, Hoppe, S, Horns, D, Jacholkowska, A, De Jager, OC, Kendziorra, E, Kerschhaggl, M, Khélifi, B, Komin, N, Kosack, K, Lamanna, G, Latham, J, Le Gallou, R, Lemière, A, Lemoine-Goumard, M, Lohse, T, Martin, JM, Martineau-Huynh, O, Marcowith, A, Masterson, C, Maurin, G, McComb, TJL, Moulin, E, De Naurois, M, Nedbal, D, Nolan, SJ, Noutsos, A, Olive, JP, Orford, KJ, Osborne, JL, Panter, M, Pelletier, G, Petrucci, PO, Pita, S, Pühlhofer, G, Punch, M, Ranchon, S, Raubenheimer, BC, Raue, M, Rayner, SM, Reimer, A, Reimer, O, Ripken, J, Rob, L, Rolland, L, Rosier-Lees, S, Rowell, G, Sahakian, V, Santangelo, A, Sauge, L, Schlenker, S, Schlickeiser, R, Schröder, R, Schwanke, U, Schwarzburg, S, Schwemmer, S, Shalchi, A, Sol, H, Spangler, D, Spanier, F, Steenkamp, R, Stegmann, C, Superina, G, Tam, PH, Tavernet, JP, Terrier, R, Tluczykont, M, Van Eldik, C, Vasileiadis, G, Venter, C, Vialle, JP, Vincent, P, Volk, HJ, Wagner, SJ & Ward, M 2007, 'Detection of extended very-high-energy γ-ray emission towards the young stellar cluster Westerlund 2', Astronomy and Astrophysics, vol. 467, no. 3, pp. 1075-1080. https://doi.org/10.1051/0004-6361:20066950

TY - JOUR

T1 - Detection of extended very-high-energy γ-ray emission towards the young stellar cluster Westerlund 2

AU - Aharonian, F.

AU - Akhperjanian, A. G.

AU - Bazer-Bachi, A. R.

AU - Beilicke, M.

AU - Benbow, W.

AU - Berge, D.

AU - Bernlöhr, K.

AU - Boisson, C.

AU - Bolz, O.

AU - Borrel, V.

AU - Braun, I.

AU - Brion, E.

AU - Brown, A. M.

AU - Bühler, R.

AU - Büsching, I.

AU - Boutelier, T.

AU - Carrigan, S.

AU - Chadwick, P. M.

AU - Chounet, L. M.

AU - Coignet, G.

AU - Cornils, R.

AU - Costamante, L.

AU - Degrange, B.

AU - Dickinson, H. J.

AU - Djannati-Ataï, A.

AU - O'C Drury, L.

AU - Dubus, G.

AU - Egberts, K.

AU - Emmanoulopoulos, D.

AU - Espigat, P.

AU - Farnier, C.

AU - Feinstein, F.

AU - Ferrero, E.

AU - Fiasson, A.

AU - Fontaine, G.

AU - Funk, Seb

AU - Funk, S.

AU - Füßling, M.

AU - Gallant, Y. A.

AU - Giebels, B.

AU - Glicenstein, J. F.

AU - Glück, B.

AU - Goret, P.

AU - Hadjichristidis, C.

AU - Hauser, D.

AU - Hauser, M.

AU - Heinzelmann, G.

AU - Henri, G.

AU - Hermann, G.

AU - Hinton, J. A.

AU - Hoffmann, A.

AU - Hofmann, W.

AU - Holleran, M.

AU - Hoppe, S.

AU - Horns, D.

AU - Jacholkowska, A.

AU - De Jager, O. C.

AU - Kendziorra, E.

AU - Kerschhaggl, M.

AU - Khélifi, B.

AU - Komin, Nu

AU - Kosack, K.

AU - Lamanna, G.

AU - Latham, J.

AU - Le Gallou, R.

AU - Lemière, A.

AU - Lemoine-Goumard, M.

AU - Lohse, T.

AU - Martin, J. M.

AU - Martineau-Huynh, O.

AU - Marcowith, A.

AU - Masterson, C.

AU - Maurin, G.

AU - McComb, T. J.L.

AU - Moulin, E.

AU - De Naurois, M.

AU - Nedbal, D.

AU - Nolan, S. J.

AU - Noutsos, A.

AU - Olive, J. P.

AU - Orford, K. J.

AU - Osborne, J. L.

AU - Panter, M.

AU - Pelletier, G.

AU - Petrucci, P. O.

AU - Pita, S.

AU - Pühlhofer, G.

AU - Punch, M.

AU - Ranchon, S.

AU - Raubenheimer, B. C.

AU - Raue, M.

AU - Rayner, S. M.

AU - Reimer, A.

AU - Reimer, O.

AU - Ripken, J.

AU - Rob, L.

AU - Rolland, L.

AU - Rosier-Lees, S.

AU - Rowell, G.

AU - Sahakian, V.

AU - Santangelo, A.

AU - Sauge, L.

AU - Schlenker, S.

AU - Schlickeiser, R.

AU - Schröder, R.

AU - Schwanke, U.

AU - Schwarzburg, S.

AU - Schwemmer, S.

AU - Shalchi, A.

AU - Sol, H.

AU - Spangler, D.

AU - Spanier, F.

AU - Steenkamp, R.

AU - Stegmann, C.

AU - Superina, G.

AU - Tam, P. H.

AU - Tavernet, J. P.

AU - Terrier, R.

AU - Tluczykont, M.

AU - Van Eldik, C.

AU - Vasileiadis, G.

AU - Venter, C.

AU - Vialle, J. P.

AU - Vincent, P.

AU - Volk, H. J.

AU - Wagner, S. J.

AU - Ward, M.

PY - 2007/1/1

Y1 - 2007/1/1

N2 - Aims. Results from γ-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 γ-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 γ-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 RCW 49. The source is detected with a statistical significance of more than 9σ, and shows extension beyond a point-like object within the HESS point-spread function. The differential γ-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) γ-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.

AB - Aims. Results from γ-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 γ-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 γ-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 RCW 49. The source is detected with a statistical significance of more than 9σ, and shows extension beyond a point-like object within the HESS point-spread function. The differential γ-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) γ-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.

KW - Gamma rays: observations

KW - ISM: HII regions

KW - ISM: individual objects: HESS J1023-575

KW - ISM: individual objects: RCW 49 (NGC 3247, G284.3-0.3)

KW - Stars: Wolf-Rayet

KW - Stars: individual: WR 20a

UR - https://www.scopus.com/pages/publications/34249992623

U2 - 10.1051/0004-6361:20066950

DO - 10.1051/0004-6361:20066950

M3 - Article

AN - SCOPUS:34249992623

SN - 0004-6361

VL - 467

SP - 1075

EP - 1080

JO - Astronomy and Astrophysics

JF - Astronomy and Astrophysics

IS - 3

ER -

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

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Keywords

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