HESS J1741−302: a hidden accelerator in the Galactic plane

H. Abdalla , A. Abramowski , F. Aharonian , F.Ait Benkhali , E.O. Angüner , M. Arakawa , C. Armand (1) , M. Arrieta (2) , M. Backes , A. Balzer , M. Barnard , Y. Becherini , J.Becker Tjus , D. Berge , S. Bernhard , K. Bernlöhr , R. Blackwell , M. Böttcher , C. Boisson (2) , J. Bolmont (3) , S. Bonnefoy , P. Bordas , J. Bregeon (4) , F. Brun (5) , P. Brun (6) , M. Bryan , M. Büchele , T. Bulik , M. Capasso , S. Caroff (7) , A. Carosi (1) , S. Casanova , M. Cerruti (3) , N. Chakraborty , R.C. G. Chaves (4) , A. Chen , J. Chevalier (1) , S. Colafrancesco , B. Condon (5) , J. Conrad , I.D. Davids , J. Decock (6) , C. Deil , J. Devin (4) , P. Dewilt , L. Dirson , A. Djannati-Ataï (8) , A. Donath , L.O'C. Drury , J. Dyks , T. Edwards , K. Egberts , G. Emery (3) , J.P. Ernenwein (9) , S. Eschbach , C. Farnier , S. Fegan (7) , M.V. Fernandes , A. Fiasson (1) , G. Fontaine (7) , S. Funk , M. Füssling , S. Gabici (8) , Y.A. Gallant (4) , T. Garrigoux , F. Gaté (1) , G. Giavitto , D. Glawion , J.F. Glicenstein (6) , D. Gottschall , M.H. Grondin (5) , J. Hahn , M. Haupt , J. Hawkes , G. Heinzelmann , G. Henri (10) , G. Hermann , J.A. Hinton , W. Hofmann , C. Hoischen , T.L. Holch , M. Holler , D. Horns , A. Ivascenko , H. Iwasaki , A. Jacholkowska (3) , M. Jamrozy , D. Jankowsky , F. Jankowsky , M. Jingo , L. Jouvin (8) , I. Jung-Richardt , M.A. Kastendieck , K. Katarzyński , M. Katsuragawa , U. Katz , D. Kerszberg (3) , D. Khangulyan , B. Khélifi (8) , J. King , S. Klepser , D. Klochkov , W. Kluźniak , Nu. Komin , K. Kosack (6) , S. Krakau , M. Kraus , P.P. Krüger , H. Laffon (5) , G. Lamanna (1) , J. Lau , J. Lefaucheur (2) , A. Lemière (8) , M. Lemoine-Goumard (5) , J.P. Lenain (3) , E. Leser , T. Lohse , M. Lorentz (6) , R. Liu , R. López-Coto , I. Lypova , D. Malyshev , V. Marandon , Alexandre Marcowith (4) , C. Mariaud (7) , R. Marx , G. Maurin (1) , N. Maxted , M. Mayer , P.J. Meintjes , M. Meyer , A.M. W. Mitchell , R. Moderski , M. Mohamed , L. Mohrmann , K. Morå , E. Moulin (6) , T. Murach , S. Nakashima , M. de Naurois (7) , H. Ndiyavala , F. Niederwanger , J. Niemiec , L. Oakes , P. O'Brien , H. Odaka , S. Ohm , M. Ostrowski , I. Oya , M. Padovani (4) , M. Panter , R.D. Parsons , N.W. Pekeur , G. Pelletier (10) , C. Perennes (3) , P.O. Petrucci (10) , B. Peyaud (6) , Q. Piel (1) , S. Pita (8) , V. Poireau (1) , D.A. Prokhorov , H. Prokoph , G. Pühlhofer , M. Punch (8) , A. Quirrenbach , S. Raab , R. Rauth , A. Reimer , O. Reimer , Matthieu Renaud (4) , R. de Los Reyes , F. Rieger , L. Rinchiuso (6) , C. Romoli , G. Rowell , B. Rudak , C.B. Rulten (2) , V. Sahakian , S. Saito , D.A. Sanchez (1) , A. Santangelo , M. Sasaki , R. Schlickeiser , F. Schüssler (6) , A. Schulz , U. Schwanke , S. Schwemmer , M. Seglar-Arroyo (6) , A.S. Seyffert , N. Shafi , I. Shilon , K. Shiningayamwe , R. Simoni , H. Sol (2) , F. Spanier , M. Spir-Jacob (8) , Ł. Stawarz , R. Steenkamp , C. Stegmann , C. Steppa , I. Sushch , T. Takahashi , J.P. Tavernet (3) , T. Tavernier (6) , A.M. Taylor , R. Terrier (8) , L. Tibaldo , D. Tiziani , M. Tluczykont , C. Trichard (9) , M. Tsirou (4) , N. Tsuji , R. Tuffs , Y. Uchiyama , D.J. van Der Walt , C. van Eldik , C. van Rensburg , B. van Soelen , George Vasileiadis (4) , J. Veh , C. Venter , A. Viana , P. Vincent (3) , J. Vink , F. Voisin , H.J. Völk , T. Vuillaume (1) , Z. Wadiasingh , S.J. Wagner , P. Wagner , R.M. Wagner , R. White , A. Wierzcholska , P. Willmann , A. Wörnlein , D. Wouters (6) , R. Yang , D. Zaborov (7) , M. Zacharias , R. Zanin , A.A. Zdziarski , A. Zech (2) , F. Zefi (7) , A. Ziegler , J. Zorn , N. Żywucka , R. Enokiya , Y. Fukui , T. Hayakawa , T. Okuda , K. Torii , H. Yamamoto

1 LAPP - Laboratoire d'Annecy de Physique des Particules
2 LUTH (UMR_8102) - Laboratoire Univers et Théories
3 LPNHE (UMR_7585) - Laboratoire de Physique Nucléaire et de Hautes Énergies
4 LUPM - Laboratoire Univers et Particules de Montpellier
5 CENBG - Centre d'Etudes Nucléaires de Bordeaux Gradignan
6 IRFU - Institut de Recherches sur les lois Fondamentales de l'Univers
7 LLR - Laboratoire Leprince-Ringuet
8 APC (UMR_7164) - AstroParticule et Cosmologie
9 CPPM - Centre de Physique des Particules de Marseille
10 IPAG - Institut de Planétologie et d'Astrophysique de Grenoble

The H.E.S.S. Collaboration has discovered a new very high energy (VHE, E > 0.1 TeV) γ-ray source, HESS J1741−302, located in the Galactic plane. Despite several attempts to constrain its nature, no plausible counterpart has been found so far at X-ray and MeV/GeV γ-ray energies, and the source remains unidentified. An analysis of 145-h of observations of HESS J1741−302 at VHEs has revealed a steady and relatively weak TeV source (~1% of the Crab Nebula flux), with a spectral index of Γ = 2.3 ± 0.2stat ± 0.2sys, extending to energies up to 10 TeV without any clear signature of a cut-off. In a hadronic scenario, such a spectrum implies an object with particle acceleration up to energies of several hundred TeV. Contrary to most H.E.S.S. unidentified sources, the angular size of HESS J1741−302 is compatible with the H.E.S.S. point spread function at VHEs, with an extension constrained to be below 0.068° at a 99% confidence level. The γ-ray emission detected by H.E.S.S. can be explained both within a hadronic scenario, due to collisions of protons with energies of hundreds of TeV with dense molecular clouds, and in a leptonic scenario, as a relic pulsar wind nebula, possibly powered by the middle-aged (20 kyr) pulsar PSR B1737−30. A binary scenario, related to the compact radio source 1LC 358.266+0.038 found to be spatially coincident with the best fit position of HESS J1741−302, is also envisaged.Key words: gamma rays: ISM / gamma rays: general / cosmic rays / ISM: clouds★★ Wallenberg Academy Fellow.

Mots clés: ISM: cosmic rays; ISM: clouds; gamma rays: observations; Gamma rays: general; gamma rays: individual objects: HESS J1741−302; gamma rays: ISM; gamma rays: general; cosmic rays; particle: acceleration; HESS; gamma ray: VHE; pulsar; galaxy; power spectrum; accelerator; signature; binary; X-ray; cloud; flux; model: hadronic; radio wave

Domaines: Astrophysique [astro-ph]

H. Abdalla, A. Abramowski, F. Aharonian, F.Ait Benkhali, E.O. Angüner, et al.. HESS J1741−302: a hidden accelerator in the Galactic plane. Astron.Astrophys., 2018, 612, pp.A13. ⟨10.1051/0004-6361/201730581⟩. ⟨hal-01797468⟩