2007A&A...467.1075A

Query : 2007A&A...467.1075A

2007A&A...467.1075A - Astronomy and Astrophysics, volume 467, 1075-1080 (2007/6-1)

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

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-ATAIE 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., FUE LING M., GALLANT Y.A., GIEBELS B., GLICENSTEIN J.F., GLUECK B., GORET P., HADJICHRISTIDIS C., HAUSER D., HAUSER M., HEINZELMANN G., HENRI G., HERMANN G., HINTON J.A., HOFFMANN A., HOFMANN W., HOLLERAN M., HOPPE S., HORNS D., JACHOLKOWSKA A., DE JAGER O.C., KENDZIORRA E., KERSCHHAGGL M., KHELIFI B., KOMIN N., KOSACK K., LAMANNA G., LATHAM I.J., LE GALLOU R., LEMIERE A., LEMOINE-GOUMARD M., LOHSE T., MARTIN J.M., MARTINEAU-HUYNH O., MARCOWITH A., MASTERSON C., MAURIN G., McCOMB T.J.L., MOULIN E., DE NAUROIS M., NEDBAL D., NOLAN S.J., NOUTSOS A., OLIVE J.-P., ORFORD K.J., OSBORNE J.L., PANTER M., PELLETIER G., PETRUCCI P.-O., PITA S., PUEHLHOFER G., PUNCH M., RANCHON S., RAUBENHEIMER B.C., RAUE M., RAYNER S.M., 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., SCHROEDER R., SCHWANKE U., SCHWARZBURG S., SCHWEMMER S., SHALCHI A., SOL H., SPANGLER D., SPANIER F., STEENKAMP R., STEGMANN C., SUPERINA G., TAM P.H., TAVERNET J.-P., TERRIER R., TLUCZYKONT M., VAN ELDIK C., VASILEIADIS G., VENTER C., VIALLE J.P., VINCENT P., VOELK H.J., WAGNER S.J. and WARD M.

Abstract (from CDS):

Result. from γ-ray observations by the HESS telescope array in the direction of the young stellar cluster Westerlund 2 are presented. 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. 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. 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.

Abstract Copyright: ∼

Journal keyword(s): 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

Simbad objects: 13

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Number of rows : 13
N Identifier Otype ICRS (J2000)
RA 		ICRS (J2000)
DEC 		Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024 		#notes
1 M 1 SNR 05 34 30.9 +22 00 53           ~ 6192 1
2 NAME Car Arm PoG 10 00 -60.0           ~ 439 1
3 3EG J1014-5705 gam 10 13 39 -57 34.1           ~ 20 1
4 PSR J1016-58 Psr 10 16 21.266 -58 57 11.70           ~ 118 3
5 SNR G284.3-01.8 Rad 10 18.3 -59 00           ~ 115 2
6 FGES J1023.3-5747 gam 10 23 15.18313 -57 46 34.7840           ~ 57 0
7 V* V712 Car EB* 10 23 58.0126366512 -57 45 48.937268268 15.466 15.473 13.5 12.6   O3If*/WN6+O3If*/WN6 171 1
8 Cl Westerlund 2 OpC 10 23 58.1 -57 45 49           ~ 356 0
9 GUM 29 HII 10 24 14.6 -57 46 58           ~ 210 0
10 WR 20b WR* 10 24 18.3978418584 -57 48 29.776921704     13.7 12.0   WN6ha 58 0
11 NGC 3247 OpC 10 25 52 -57 55.6   7.99 7.6     ~ 38 0
12 NGC 3603 OpC 11 15 10.8 -61 15 32           ~ 1067 1
13 Cl Westerlund 1 Cl* 16 47 02.4 -45 51 07           ~ 566 0

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