Evidence of 100 TeV $\gamma$-ray emission from HESS J1702-420: A new PeVatron candidate

H. Abdalla , F. Aharonian , F. Ait Benkhali , E.O. Angüner (1) , C. Arcaro , C. Armand (2) , T. Armstrong , H. Ashkar (3) , M. Backes , V. Baghmanyan , V. Barbosa Martins , A. Barnacka , M. Barnard , Y. Becherini , D. Berge , K. Bernlöhr , B. Bi , M. Böttcher , C. Boisson (4) , J. Bolmont (5) , M. de Bony de Lavergne (2) , M. Breuhaus , F. Brun (3) , P. Brun (3) , M. Bryan , M. Büchele , T. Bulik , T. Bylund , S. Caroff (2) , A. Carosi (2) , S. Casanova , T. Chand , S. Chandra , A. Chen , G. Cotter , M. Curyło , J. Damascene Mbarubucyeye , I.D. Davids , J. Davies , C. Deil , J. Devin (6) , L. Dirson , A. Djannati-Ataï (6) , A. Dmytriiev (4) , A. Donath , V. Doroshenko , L. Dreyer , C. Duffy , J. Dyks , K. Egberts , F. Eichhorn , S. Einecke , G. Emery (5) , J.-P. Ernenwein (1) , K. Feijen , S. Fegan (7) , A. Fiasson (2) , G. Fichet de Clairfontaine (4) , G. Fontaine (7) , S. Funk , M. Füssling , S. Gabici (6) , Y.A. Gallant (8) , G. Giavitto , L. Giunti (6, 3) , D. Glawion , J.F. Glicenstein (3) , M.-H. Grondin (9) , J. Hahn , M. Haupt , G. Hermann , J.A. Hinton , W. Hofmann , C. Hoischen , T.L. Holch , M. Holler , M. Hörbe , D. Horns , D. Huber , M. Jamrozy , D. Jankowsky , F. Jankowsky , A. Jardin-Blicq , V. Joshi , I. Jung-Richardt , E. Kasai , M.A. Kastendieck , K. Katarzyński , U. Katz , D. Khangulyan , B. Khélifi (6) , S. Klepser , W. Kluźniak , Nu. Komin , R. Konno , K. Kosack (3) , D. Kostunin , M. Kreter , G. Lamanna (2) , A. Lemière (6) , M. Lemoine-Goumard (9) , J.-P. Lenain (5) , F. Leuschner , C. Levy (5) , T. Lohse , I. Lypova , J. Mackey , J. Majumdar , D. Malyshev , V. Marandon , P. Marchegiani , Alexandre Marcowith (8) , A. Mares (9) , G. Martí-Devesa , R. Marx , G. Maurin (2) , P.J. Meintjes , M. Meyer , A. Mitchell , R. Moderski , L. Mohrmann , A. Montanari (3) , C. Moore , P. Morris , E. Moulin (3) , J. Muller (7) , T. Murach , K. Nakashima , A. Nayerhoda , M. de Naurois (7) , H. Ndiyavala , J. Niemiec , L. Oakes , P. O'Brien , H. Odaka , S. Ohm , L. Olivera-Nieto , E. de Ona Wilhelmi , M. Ostrowski , S. Panny , M. Panter , R.D. Parsons , G. Peron , B. Peyaud (3) , Q. Piel (2) , S. Pita (6) , V. Poireau (2) , A. Priyana Noel , D.A. Prokhorov , H. Prokoph , G. Pühlhofer , M. Punch (6) , A. Quirrenbach , S. Raab , R. Rauth , P. Reichherzer (3) , A. Reimer , O. Reimer , Q. Remy , Matthieu Renaud (8) , F. Rieger , L. Rinchiuso (3) , C. Romoli , G. Rowell , B. Rudak , E. Ruiz-Velasco , V. Sahakian , S. Sailer , H. Salzmann , D.A. Sanchez (2) , A. Santangelo , M. Sasaki , M. Scalici , J. Schäfer , F. Schüssler (3) , H.M. Schutte , U. Schwanke , M. Seglar-Arroyo (3) , M. Senniappan , A.S. Seyffert , N. Shafi , J.N.S. Shapopi , K. Shiningayamwe , R. Simoni , A. Sinha (6) , H. Sol (4) , A. Specovius , S. Spencer , M. Spir-Jacob (6) , L. Stawarz , L. Sun , R. Steenkamp , C. Stegmann , S. Steinmassl , C. Steppa , T. Takahashi , T. Tavernier (3) , A.M. Taylor , R. Terrier (6) , J.H.E. Thiersen , D. Tiziani , M. Tluczykont , L. Tomankova , C. Trichard (7) , M. Tsirou , R. Tuffs , Y. Uchiyama , D.J. van Der Walt , C. van Eldik , C. van Rensburg , B. van Soelen , George Vasileiadis (8) , J. Veh , C. Venter , P. Vincent (5) , J. Vink , H.J. Völk , Z. Wadiasingh , S.J. Wagner , J. Watson , Felix Werner , R. White , A. Wierzcholska , Yu Wun Wong , A. Yusafzai , M. Zacharias (4) , R. Zanin , D. Zargaryan , A.A. Zdziarski , A. Zech (4) , S.J. Zhu , J. Zorn , S. Zouari (6) , N. Żywucka , F. Acero (3)

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

The identification of PeVatrons, hadronic particle accelerators reaching the knee of the cosmic ray spectrum (few $10^{15}$ eV), is crucial to understand the origin of cosmic rays in the Galaxy. We provide an update on the unidentified source HESS J1702-420, a promising PeVatron candidate. We present new observations of HESS J1702-420 made with the High Energy Stereoscopic System (H.E.S.S.), and processed using improved analysis techniques. The analysis configuration was optimized to enhance the collection area at the highest energies. We applied a three-dimensional (3D) likelihood analysis to model the source region and adjust non thermal radiative spectral models to the $\gamma$-ray data. We also analyzed archival data from the Fermi Large Area Telescope (LAT) to constrain the source spectrum at $\gamma$-ray energies >10 GeV. We report the detection of a new source component called HESS J1702-420A, that was separated from the bulk of TeV emission at a $5.4\sigma$ confidence level. The power law $\gamma$-ray spectrum of HESS J1702-420A extends with an index of $\Gamma=1.53\pm0.19_\text{stat}\pm0.20_\text{sys}$ and without curvature up to the energy band 64-113 TeV, in which it was detected by H.E.S.S. at a $4.0\sigma$ confidence level. This brings evidence for the source emission up to $100\,\text{TeV}$, which makes HESS J1702-420A a compelling candidate site for the presence of extremely high energy cosmic rays. Remarkably, in a hadronic scenario, the cut-off energy of the proton distribution powering HESS J1702-420A is found to be higher than 0.5 PeV at a 95% confidence level. HESS J1702-420A becomes therefore one of the most solid PeVatron candidates detected so far in H.E.S.S. data, altough a leptonic origin of its emission could not be ruled out either.

Mots clés: cosmic radiation: spectrum; energy: high; p: energy; cosmic radiation: UHE; gamma ray: energy spectrum; dimension: 3; HESS; TeV; GLAST; acceleration; curvature; spectral; solids; galaxy; site; 5/3; GeV

Domaines: Astrophysique [astro-ph]

H. Abdalla, F. Aharonian, F. Ait Benkhali, E.O. Angüner, C. Arcaro, et al.. Evidence of 100 TeV $\gamma$-ray emission from HESS J1702-420: A new PeVatron candidate. Astronomy and Astrophysics - A&A, 2021, 653, pp.A152. ⟨10.1051/0004-6361/202140962⟩. ⟨hal-03263207⟩