Spectral Study of Very-high-energy Gamma Rays from SS 433 with HAWC
R. Alfaro, C. Alvarez, J. C. Arteaga-Velázquez, D. Avila Rojas, H. A. Ayala Solares, Rishi Babu, E. Belmont‐Moreno, Argelia Bernal, K. S. Caballero‐Mora, T. Capistrán, A. Carramiñana, S. Casanova, J. Cotzomi, E. De la Fuente, Davide Depaoli, Niccolò Di Lalla, R. Díaz Hernández, B. L. Dingus, M. A. DuVernois, K. Engel, T. Ergin, C. Espinoza, Kwok Lung Fan, Ke Fang, N. Fraija, S. Fraija, J. A. García-González, A. Gonzalez Muñoz, M. M. González, J. A. Goodman, S. Groetsch, J. P. Harding, Sergio Hernández Cadena, I. Herzog, Dezhi Huang, F. Hueyotl‐Zahuantitla, Petra Huentemeyer, A. Iriarte, S. Kaufmann, A. Lara, William H. Lee, J. S. H. Lee, C. de León, H. León Vargas, A. L. Longinotti, G. Luis-Raya, K. Malone, J. Martínez-Castro, J. A. Matthews, P. Miranda-Romagnoli, J. A. Montes, E. Moreno, M. Mostafá, L. Nellen, M. U. Nisa, R. Noriega-Papaqui, Y. Pérez Araujo, E. G. Pérez‐Pérez, Chang Dong Rho, D. Rosa‐González, E. Ruiz-Velasco, Humberto Antonio Salazar Ibarguen, A. Sandoval, M. Schneider, J. Serna-Franco, A. J. Smith, Y. Son, R. W. Springer, O. Tibolla, Kirsten Tollefson, I. Torres, R. Torres-Escobedo, Rhiannon M. Turner, F. Ureña-Mena, Enrique Varela, L. Villaseñor, X. Wang, Z. Wang, I. J. Watson, S. Yu, S. Yun-Cárcamo, H. Zhou
Abstract
Abstract Very-high-energy (0.1–100 TeV) gamma-ray emissions were observed in High-Altitude Water Cherenkov (HAWC) data from the lobes of the microquasar SS 433, making them the first set of astrophysical jets that were resolved at TeV energies. In this work, we update the analysis of SS 433 using 2565 days of data from the HAWC observatory. Our analysis reports the detection of a point-like source in the east lobe at a significance of 6.6 σ and in the west lobe at a significance of 8.2 σ . For each jet lobe, we localize the gamma-ray emission and identify a best-fit position. The locations are close to the X-ray emission sites “e1” and “w1” for the east and west lobes, respectively. We analyze the spectral energy distributions and find that the energy spectra of the lobes are consistent with a simple power law d N / d E ∝ E α with <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>α</mml:mi> <mml:mo>=</mml:mo> <mml:mo>−</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>2.44</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.12</mml:mn> <mml:mo>−</mml:mo> <mml:mn>0.04</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.13</mml:mn> <mml:mo>+</mml:mo> <mml:mn>0.04</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>α</mml:mi> <mml:mo>=</mml:mo> <mml:mo>−</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>2.35</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.11</mml:mn> <mml:mo>−</mml:mo> <mml:mn>0.03</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.12</mml:mn> <mml:mo>+</mml:mo> <mml:mn>0.03</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> for the east and west lobes, respectively. The maximum energy of photons from the east and west lobes reaches 56 TeV and 123 TeV, respectively. We compare our observations to various models and conclude that the very-high-energy gamma-ray emission can be produced by a population of electrons that were efficiently accelerated.