Very-high-energy gamma-ray emission from the direction of the Galactic globular cluster Terzan 5

A. Abramowski; F. Acero; F. Aharonian; A. G. Akhperjanian; G. Anton; A. Balzer; A. Barnacka; U. Barres de Almeida; Y. Becherini; J. Becker; B. Behera; K. Bernlöhr; A. Bochow; C. Boisson; J. Bolmont; P. Bordas; J. Brucker; F. Brun; P. Brun; T. Bulik; I. Büsching; S. Carrigan; S. Casanova; M. Cerruti; P. M. Chadwick; A. Charbonnier; R. C. G. Chaves; A. Cheesebrough; L.-M. Chounet; A. C. Clapson; G. Coignet; G. Cologna; J. Conrad; M. Dalton; M. K. Daniel; I. D. Davids; B. Degrange; C. Deil; H. J. Dickinson; A. Djannati-Ataï; W. Domainko; L. O’C. Drury; F. Dubois; G. Dubus; K. Dutson; J. Dyks; M. Dyrda; K. Egberts; P. Eger; P. Espigat; L. Fallon; C. Farnier; S. Fegan; F. Feinstein; M. V. Fernandes; A. Fiasson; G. Fontaine; A. Förster; M. Füßling; Y. A. Gallant; H. Gast; L. Gérard; D. Gerbig; B. Giebels; J. F. Glicenstein; B. Glück; P. Goret; D. Göring; S. Häffner; J. D. Hague; D. Hampf; M. Hauser; S. Heinz; G. Heinzelmann; G. Henri; G. Hermann; J. A. Hinton; A. Hoffmann; W. Hofmann; P. Hofverberg; M. Holler; D. Horns; A. Jacholkowska; O. C. de Jager; C. Jahn; M. Jamrozy; I. Jung; M. A. Kastendieck; K. Katarzyński; U. Katz; S. Kaufmann; D. Keogh; D. Khangulyan; B. Khélifi; D. Klochkov; W. Kluźniak; T. Kneiske; Nu. Komin; K. Kosack; R. Kossakowski; H. Laffon; G. Lamanna; D. Lennarz; T. Lohse; A. Lopatin; C.-C. Lu; V. Marandon; A. Marcowith; J. Masbou; D. Maurin; N. Maxted; T. J. L. McComb; M. C. Medina; J. Méhault; N. Nguyen; R. Moderski; E. Moulin; C. L. Naumann; M. Naumann-Godo; M. de Naurois; D. Nedbal; D. Nekrassov; B. Nicholas; J. Niemiec; S. J. Nolan; S. Ohm; E. de Oña Wilhelmi; B. Opitz; M. Ostrowski; I. Oya; M. Panter; M. Paz Arribas; G. Pedaletti; G. Pelletier; P.-O. Petrucci; S. Pita; G. Pühlhofer; M. Punch; A. Quirrenbach; M. Raue; S. M. Rayner; A. Reimer; O. Reimer; M. Renaud; R. de los Reyes; F. Rieger; J. Ripken; L. Rob; S. Rosier-Lees; G. Rowell; B. Rudak; C. B. Rulten; J. Ruppel; F. Ryde; V. Sahakian; A. Santangelo; R. Schlickeiser; F. M. Schöck; A. Schulz; U. Schwanke; S. Schwarzburg; S. Schwemmer; M. Sikora; J. L. Skilton; H. Sol; G. Spengler; Ł. Stawarz; R. Steenkamp; C. Stegmann; F. Stinzing; K. Stycz; I. Sushch; A. Szostek; J.-P. Tavernet; R. Terrier; M. Tluczykont; K. Valerius; C. van Eldik; G. Vasileiadis; C. Venter; J. P. Vialle; A. Viana; P. Vincent; H. J. Völk; F. Volpe; S. Vorobiov; M. Vorster; S. J. Wagner; M. Ward; R. White; A. Wierzcholska; M. Zacharias; A. Zajczyk; A. A. Zdziarski; A. Zech; H.-S. Zechlin

doi:10.1051/0004-6361/201117171

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Volume 531 (July 2011)

A&A, 531 (2011) L18

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Issue		A&A Volume 531, July 2011


Article Number		L18
Number of page(s)		5
Section		Letters
DOI		https://doi.org/10.1051/0004-6361/201117171
Published online		07 July 2011

A&A 531, L18 (2011)

Letter to the Editor

Very-high-energy gamma-ray emission from the direction of the Galactic globular cluster Terzan 5

H.E.S.S. Collaboration
A. Abramowski¹, F. Acero², F. Aharonian³^,4^,5, A. G. Akhperjanian⁶^,5, G. Anton⁷, A. Balzer⁷, A. Barnacka⁸^,9, U. Barres de Almeida¹⁰^,⋆, Y. Becherini¹¹^,12, J. Becker¹³, B. Behera¹⁴, K. Bernlöhr³^,15, A. Bochow³, C. Boisson¹⁶, J. Bolmont¹⁷, P. Bordas¹⁸, J. Brucker⁷, F. Brun¹², P. Brun⁹, T. Bulik¹⁹, I. Büsching²⁰^,13, S. Carrigan³, S. Casanova¹³, M. Cerruti¹⁶, P. M. Chadwick¹⁰, A. Charbonnier¹⁷, R. C. G. Chaves³, A. Cheesebrough¹⁰, L.-M. Chounet¹², A. C. Clapson³^,⋆⋆, G. Coignet²¹, G. Cologna¹⁴, J. Conrad²², M. Dalton¹⁵, M. K. Daniel¹⁰, I. D. Davids²³, B. Degrange¹², C. Deil³, H. J. Dickinson²², A. Djannati-Ataï¹¹, W. Domainko³, L. O’C. Drury⁴, F. Dubois²¹, G. Dubus²⁴, K. Dutson²⁵, J. Dyks⁸, M. Dyrda²⁶, K. Egberts²⁷, P. Eger⁷, P. Espigat¹¹, L. Fallon⁴, C. Farnier², S. Fegan¹², F. Feinstein², M. V. Fernandes¹, A. Fiasson²¹, G. Fontaine¹², A. Förster³, M. Füßling¹⁵, Y. A. Gallant², H. Gast³, L. Gérard¹¹, D. Gerbig¹³, B. Giebels¹², J. F. Glicenstein⁹, B. Glück⁷, P. Goret⁹, D. Göring⁷, S. Häffner⁷, J. D. Hague³, D. Hampf¹, M. Hauser¹⁴, S. Heinz⁷, G. Heinzelmann¹, G. Henri²⁴, G. Hermann³, J. A. Hinton²⁵, A. Hoffmann¹⁸, W. Hofmann³, P. Hofverberg³, M. Holler⁷, D. Horns¹, A. Jacholkowska¹⁷, O. C. de Jager²⁰, C. Jahn⁷, M. Jamrozy²⁸, I. Jung⁷, M. A. Kastendieck¹, K. Katarzyński²⁹, U. Katz⁷, S. Kaufmann¹⁴, D. Keogh¹⁰, D. Khangulyan³, B. Khélifi¹², D. Klochkov¹⁸, W. Kluźniak⁸, T. Kneiske¹, Nu. Komin²¹, K. Kosack⁹, R. Kossakowski²¹, H. Laffon¹², G. Lamanna²¹, D. Lennarz³, T. Lohse¹⁵, A. Lopatin⁷, C.-C. Lu³, V. Marandon¹¹, A. Marcowith², J. Masbou²¹, D. Maurin¹⁷, N. Maxted³⁰, T. J. L. McComb¹⁰, M. C. Medina⁹, J. Méhault², N. Nguyen¹, R. Moderski⁸, E. Moulin⁹, C. L. Naumann¹⁷, M. Naumann-Godo⁹, M. de Naurois¹², D. Nedbal³¹, D. Nekrassov³, B. Nicholas³⁰, J. Niemiec²⁶, S. J. Nolan¹⁰, S. Ohm³²^,25^,3, E. de Oña Wilhelmi³, B. Opitz¹, M. Ostrowski²⁸, I. Oya¹⁵, M. Panter³, M. Paz Arribas¹⁵, G. Pedaletti¹⁴, G. Pelletier²⁴, P.-O. Petrucci²⁴, S. Pita¹¹, G. Pühlhofer¹⁸, M. Punch¹¹, A. Quirrenbach¹⁴, M. Raue¹, S. M. Rayner¹⁰, A. Reimer²⁷, O. Reimer²⁷, M. Renaud², R. de los Reyes³, F. Rieger³^,33, J. Ripken²², L. Rob³¹, S. Rosier-Lees²¹, G. Rowell³⁰, B. Rudak⁸, C. B. Rulten¹⁰, J. Ruppel¹³, F. Ryde³⁴, V. Sahakian⁶^,5, A. Santangelo¹⁸, R. Schlickeiser¹³, F. M. Schöck⁷, A. Schulz⁷, U. Schwanke¹⁵, S. Schwarzburg¹⁸, S. Schwemmer¹⁴, M. Sikora⁸, J. L. Skilton³², H. Sol¹⁶, G. Spengler¹⁵, Ł. Stawarz²⁸, R. Steenkamp²³, C. Stegmann⁷, F. Stinzing⁷, K. Stycz⁷, I. Sushch¹⁵^,⋆⋆⋆, A. Szostek²⁸, J.-P. Tavernet¹⁷, R. Terrier¹¹, M. Tluczykont¹, K. Valerius⁷, C. van Eldik³, G. Vasileiadis², C. Venter²⁰, J. P. Vialle²¹, A. Viana⁹, P. Vincent¹⁷, H. J. Völk³, F. Volpe³, S. Vorobiov², M. Vorster²⁰, S. J. Wagner¹⁴, M. Ward¹⁰, R. White²⁵, A. Wierzcholska²⁸, M. Zacharias¹³, A. Zajczyk⁸^,2, A. A. Zdziarski⁸, A. Zech¹⁶ and H.-S. Zechlin¹

¹ Universität Hamburg, Institut für Experimentalphysik, Luruper Chaussee 149, 22761 Hamburg, Germany
² Laboratoire Univers et Particules de Montpellier, Université Montpellier 2, CNRS/IN2P3, CC 72, Place Eugène Bataillon, 34095 Montpellier Cedex 5, France
³ Max-Planck-Institut für Kernphysik, PO Box 103980, 69029 Heidelberg, Germany
e-mail: clapson@mpi-hd.mpg.de; domainko@mpi-hd.mpg.de
⁴ Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, Dublin 2, Ireland
⁵ National Academy of Sciences of the Republic of Armenia, Yerevan
⁶ Yerevan Physics Institute, 2 Alikhanian Brothers St., 375036 Yerevan, Armenia
⁷ Universität Erlangen-Nürnberg, Physikalisches Institut, Erwin-Rommel-Str. 1, 91058 Erlangen, Germany
⁸ Nicolaus Copernicus Astronomical Center, ul. Bartycka 18, 00-716 Warsaw, Poland
⁹ CEA Saclay, DSM/IRFU, 91191 Gif-Sur-Yvette Cedex, France
¹⁰ University of Durham, Department of Physics, South Road, Durham DH1 3LE, UK
¹¹ 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)
¹² Laboratoire Leprince-Ringuet, Ecole Polytechnique, CNRS/IN2P3, 91128 Palaiseau, France
¹³ Institut für Theoretische Physik, Lehrstuhl IV: Weltraum und Astrophysik, Ruhr-Universität Bochum, 44780 Bochum, Germany
¹⁴ Landessternwarte, Universität Heidelberg, Königstuhl, 69117 Heidelberg, Germany
¹⁵ Institut für Physik, Humboldt-Universität zu Berlin, Newtonstr. 15, 12489 Berlin, Germany
¹⁶ LUTH, Observatoire de Paris, CNRS, Université Paris Diderot, 5 place Jules Janssen, 92190 Meudon, France
¹⁷ LPNHE, Université Pierre et Marie Curie Paris 6, Université Denis Diderot Paris 7, CNRS/IN2P3, 4 place Jussieu, 75252, Paris Cedex 5, France
¹⁸ Institut für Astronomie und Astrophysik, Universität Tübingen, Sand 1, 72076 Tübingen, Germany
¹⁹ Astronomical Observatory, The University of Warsaw, Al. Ujazdowskie 4, 00-478 Warsaw, Poland
²⁰ Unit for Space Physics, North-West University, Potchefstroom 2520, South Africa
²¹ Laboratoire d’Annecy-le-Vieux de Physique des Particules, Université de Savoie, CNRS/IN2P3, 74941 Annecy-le-Vieux, France
²² Oskar Klein Centre, Department of Physics, Stockholm University, Albanova University Center, 10691 Stockholm, Sweden
²³ University of Namibia, Department of Physics, Private Bag 13301, Windhoek, Namibia
²⁴ Laboratoire d’Astrophysique de Grenoble, INSU/CNRS, Université Joseph Fourier, BP 53, 38041 Grenoble Cedex 9, France
²⁵ Department of Physics and Astronomy, The University of Leicester, University Road, Leicester, LE1 7RH, UK
²⁶ Instytut Fizyki Ja¸drowej PAN, ul. Radzikowskiego 152, 31-342 Kraków, Poland
²⁷ Institut für Astro- und Teilchenphysik, Leopold-Franzens-Universität Innsbruck, 6020 Innsbruck, Austria
²⁸ Obserwatorium Astronomiczne, Uniwersytet Jagielloński, ul. Orla 171, 30-244 Kraków, Poland
²⁹ Toruń Centre for Astronomy, Nicolaus Copernicus University, ul. Gagarina 11, 87-100 Toruń, Poland
³⁰ School of Chemistry & Physics, University of Adelaide, Adelaide 5005, Australia
³¹ Charles University, Faculty of Mathematics and Physics, Institute of Particle and Nuclear Physics, V Holešovičkách 2, 180 00 Prague 8, Czech Republic
³² School of Physics & Astronomy, University of Leeds, Leeds LS2 9JT, UK
³³ European Associated Laboratory for Gamma-Ray Astronomy, jointly supported by CNRS and MPG
³⁴ Oskar Klein Centre, Department of Physics, Royal Institute of Technology (KTH), Albanova, 10691 Stockholm, Sweden

Received: 2 May 2011
Accepted: 16 June 2011

Abstract

The HESS very-high-energy (VHE, E > 0.1 TeV) gamma-ray telescope system has discovered a new source, HESS J1747-248. The measured integral flux is (1.2 ± 0.3) × 10^-12 cm^-2 s^-1 above 440 GeV for a power-law photon spectral index of 2.5 ± 0.3_stat ± 0.2_sys. The VHE gamma-ray source is located in the close vicinity of the Galactic globular cluster Terzan 5 and extends beyond the HESS point spread function (0.07°). The probability of a chance coincidence with Terzan 5 and an unrelated VHE source is quite low (~10^-4). With the largest population of identified millisecond pulsars (msPSRs), a very high core stellar density and the brightest GeV range flux as measured by Fermi-LAT, Terzan 5 stands out among Galactic globular clusters. The properties of the VHE source are briefly discussed in the context of potential emission mechanisms, notably in relation to msPSRs. Interpretation of the available data accommodates several possible origins for this VHE gamma-ray source, although none of them offers a satisfying explanation of its peculiar morphology.

Key words: globular clusters: individual: Terzan 5 / radiation mechanisms: non-thermal / pulsars: general / gamma rays: general

^⋆

Supported by CAPES Foundation, Ministry of Education of Brazil.

^⋆⋆

Corresponding author.

^⋆⋆⋆

Supported by Erasmus Mundus, External Cooperation Window.

© ESO, 2011

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