Observation of the Galactic Center PeVatron beyond 100 TeV with HAWC

Abstract We report an observation of ultrahigh-energy (UHE) gamma rays from the Galactic center (GC) region, using 7 yr of data collected by the High-Altitude Water Cherenkov (HAWC) Observatory. The HAWC data are best described as a point-like source (HAWC J1746-2856) with a power-law spectrum ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi mathvariant="italic">d</mml:mi> <mml:mi>N</mml:mi> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:mi mathvariant="italic">d</mml:mi> <mml:mi>E</mml:mi> <mml:mo>=</mml:mo> <mml:mi>ϕ</mml:mi> <mml:msup> <mml:mrow> <mml:mfenced close=")" open="("> <mml:mrow> <mml:mi>E</mml:mi> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:mn>26</mml:mn> <mml:mspace width="0.25em"/> <mml:mi>TeV</mml:mi> </mml:mrow> </mml:mfenced> </mml:mrow> <mml:mrow> <mml:mi>γ</mml:mi> </mml:mrow> </mml:msup> </mml:math> ), where γ = −2.88 ± 0.15 stat − 0.1 sys and ϕ = 1.5 × 10 −15 (TeV cm 2 s) −1 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo>±</mml:mo> <mml:msub> <mml:mrow> <mml:mn>0.3</mml:mn> </mml:mrow> <mml:mrow> <mml:mi>stat</mml:mi> </mml:mrow> </mml:msub> <mml:msubsup> <mml:mrow> <mml:mspace width="0.25em"/> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:msub> <mml:mrow> <mml:mn>0.13</mml:mn> </mml:mrow> <mml:mrow> <mml:mi>sys</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:msub> <mml:mrow> <mml:mn>0.08</mml:mn> </mml:mrow> <mml:mrow> <mml:mi>sys</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> </mml:msubsup> </mml:math> extending from 6 to 114 TeV. We find no evidence of a spectral cutoff up to 100 TeV using HAWC data. Two known point-like gamma-ray sources are spatially coincident with the HAWC gamma-ray excess: Sgr A* (HESS J1745-290) and the Arc (HESS J1746-285). We subtract the known flux contribution of these point sources from the measured flux of HAWC J1746-2856 to exclude their contamination and show that the excess observed by HAWC remains significant (&gt;5 σ ), with the spectrum extending to &gt;100 TeV. Our result supports that these detected UHE gamma rays can originate via hadronic interaction of PeV cosmic-ray protons with the dense ambient gas and confirms the presence of a proton PeVatron at the GC.

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Publication Details

Journal
The Astrophysical Journal Letters
Published
2024-09-01
DOI
https://doi.org/10.3847/2041-8213/ad772e
Citations
12
Primary Topic
Astrophysics and Cosmic Phenomena
Type
article
Field-Weighted Citation Impact
7.92
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article

Observation of the Galactic Center PeVatron beyond 100 TeV with HAWC

H. Zhou, F. Ureña-Mena, Rishi Babu, S. Coutinõ de León et al.
12 citations
The Astrophysical Journal Letters
Astrophysics and Cosmic Phenomena
7.92
article

Observation of the Galactic Center PeVatron beyond 100 TeV with HAWC

H. Zhou, F. Ureña-Mena, Rishi Babu, S. Coutinõ de León, A. Lara, K. Tollefson, J. A. Hinton, C. Alvarez, Enrique Varela, E. Moreno, Y. Pérez Araujo, E. Willox, A. Sandoval, E. De la Fuente, U. Cotti, I. Herzog, J. C. Díaz–Vélez, Dezhi Huang, K. Malone, S. Casanova, W. H. Lee, L. Nellen, P. Miranda-Romagnoli, J. A. Goodman, Shaoqing Yu, M. Newbold, O. Tibolla, E. Ruiz-Velasco, X. Wang, H. R. Wu, Laura Olivera-Nieto, Y. Son, R. Alfaro, I. Torres, E. G. Pérez‐Pérez, Rhiannon M. Turner, C. Espinoza, N. Di Lalla, B. L. Dingus, D. Kieda, T. Capistrán, K. S. Caballero‐Mora, R. W. Springer, Jorge Alexis Montes, Chang Dong Rho, R. Noriega-Papaqui, F. Garfias, D. Rosa‐González, R. Torres-Escobedo, A. L. Longinotti, F. Hueyotl‐Zahuantitla, A. Iriarte, Georg Schwefer, M. A. DuVernois, Amado Andrés, G. Luis-Raya, T. Ergin, T. B. Humensky, D. Salazar-Gallegos, J. P. Harding, M. Osorio-Archila, E. Belmont-Moreno, Magda Gonzalez, J. A. Morales-Soto, J. Martínez-Castro, M. Mostafá, J. A. García-González, Hazal Goksu, C. de León, K. Engel, Kwok Lung Fan, J. A. Matthews, J. Serna-Franco, N. Omodei, S. Hernández-Cadena, Davide Depaoli, H. A. Ayala Solares, N. Fraija, S. Yun-Cárcamo, S. Fraija, M. Najafi, O. Martı́nez, J. Cotzomi, D. Avila Rojas, A. Carramiñana, A. J. Smith, I. J. Watson, R. Diaz Hernandez, M. U. Nisa, H. León Vargas, Humberto Antonio Salazar Ibarguen, P. Hüntemeyer, J. C. Arteaga-Velázquez, A. Albert, M. Schneider, S. Groetsch, S. Kaufmann, Z. Wang, J. T. Linnemann, A. Bernal, J. Lee
article en
12 citations

Abstract

Abstract We report an observation of ultrahigh-energy (UHE) gamma rays from the Galactic center (GC) region, using 7 yr of data collected by the High-Altitude Water Cherenkov (HAWC) Observatory. The HAWC data are best described as a point-like source (HAWC J1746-2856) with a power-law spectrum ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi mathvariant="italic">d</mml:mi> <mml:mi>N</mml:mi> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:mi mathvariant="italic">d</mml:mi> <mml:mi>E</mml:mi> <mml:mo>=</mml:mo> <mml:mi>ϕ</mml:mi> <mml:msup> <mml:mrow> <mml:mfenced close=")" open="("> <mml:mrow> <mml:mi>E</mml:mi> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:mn>26</mml:mn> <mml:mspace width="0.25em"/> <mml:mi>TeV</mml:mi> </mml:mrow> </mml:mfenced> </mml:mrow> <mml:mrow> <mml:mi>γ</mml:mi> </mml:mrow> </mml:msup> </mml:math> ), where γ = −2.88 ± 0.15 stat − 0.1 sys and ϕ = 1.5 × 10 −15 (TeV cm 2 s) −1 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo>±</mml:mo> <mml:msub> <mml:mrow> <mml:mn>0.3</mml:mn> </mml:mrow> <mml:mrow> <mml:mi>stat</mml:mi> </mml:mrow> </mml:msub> <mml:msubsup> <mml:mrow> <mml:mspace width="0.25em"/> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:msub> <mml:mrow> <mml:mn>0.13</mml:mn> </mml:mrow> <mml:mrow> <mml:mi>sys</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:msub> <mml:mrow> <mml:mn>0.08</mml:mn> </mml:mrow> <mml:mrow> <mml:mi>sys</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> </mml:msubsup> </mml:math> extending from 6 to 114 TeV. We find no evidence of a spectral cutoff up to 100 TeV using HAWC data. Two known point-like gamma-ray sources are spatially coincident with the HAWC gamma-ray excess: Sgr A* (HESS J1745-290) and the Arc (HESS J1746-285). We subtract the known flux contribution of these point sources from the measured flux of HAWC J1746-2856 to exclude their contamination and show that the excess observed by HAWC remains significant (&gt;5 σ ), with the spectrum extending to &gt;100 TeV. Our result supports that these detected UHE gamma rays can originate via hadronic interaction of PeV cosmic-ray protons with the dense ambient gas and confirms the presence of a proton PeVatron at the GC.

The Astrophysical Journal LettersVol. 973(1)
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Astrophysics and Cosmic Phenomena
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