Long-term Spectra of the Blazars Mrk 421 and Mrk 501 at TeV Energies Seen by HAWC
A. Albert, R. Alfaro, C. Álvarez, José Roberto Ángeles Camacho, J. C. Arteaga‐Velázquez, K. P. Arunbabu, D. Avila Rojas, H. A. Ayala Solares, Vardan Baghmanyan, E. Belmont‐Moreno, K. S. Caballero‐Mora, T. Capistrán, A. Carramiñana, S. Casanova, U. Cotti, J. Cotzomi, S. Coutinõ de León, E. De la Fuente, R. Díaz Hernández, M. A. DuVernois, Mora Durocher, J. C. Díaz–Vélez, K. Engel, C. Espinoza, Kwok Lung Fan, M. Fernández Alonso, N. Fraija, D. García, J. A. García-González, F. Garfias, M. M. González, J. A. Goodman, J. P. Harding, B. Hona, D. Huang, F. Hueyotl‐Zahuantitla, P. Hüntemeyer, A. Iriarte, Vikas Joshi, A. Lara, William H. Lee, J. S. H. Lee, H. León Vargas, J. T. Linneman, A. L. Longinotti, G. Luis-Raya, K. Malone, O. Martı́nez, J. Martínez-Castro, J. A. Matthews, P. Miranda-Romagnoli, E. Moreno, M. Mostafá, A. Nayerhoda, L. Nellen, M. Newbold, R. Noriega-Papaqui, Alison Peisker, Y. Pérez Araujo, E. G. Pérez‐Pérez, Chang Dong Rho, D. Rosa‐González, H. Salazar, F. Salesa Greus, A. Sandoval, M. Schneider, José Serna-Franco, A. J. Smith, R. W. Springer, Kirsten Tollefson, I. Torres, R. Torres-Escobedo, F. Ureña-Mena, L. Villaseñor, X. Wang, T. Weisgarber, E. Willox, H. Zhou, C. de León
Abstract
Abstract The High Altitude Water Cherenkov (HAWC) Gamma-Ray Observatory surveys the very high-energy sky in the 300 GeV to >100 TeV energy range. HAWC has detected two blazars above 11 σ , Markarian 421 (Mrk 421) and Markarian 501 (Mrk 501). The observations are comprised of data taken in the period between 2015 June and 2018 July, resulting in ∼1038 days of exposure. In this work, we report the time-averaged spectral analyses for both sources, above 0.5 TeV. Taking into account the flux attenuation due to the extragalactic background light, the intrinsic spectrum of Mrk 421 is described by a power law with an exponential energy cutoff with index <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>α</mml:mi> <mml:mo>=</mml:mo> <mml:mn>2.26</mml:mn> <mml:mo>±</mml:mo> <mml:msub> <mml:mrow> <mml:mfenced close=")" open="("> <mml:mrow> <mml:mn>0.12</mml:mn> </mml:mrow> </mml:mfenced> </mml:mrow> <mml:mrow> <mml:mi>stat</mml:mi> </mml:mrow> </mml:msub> <mml:msub> <mml:mrow> <mml:mfenced close=")" open="("> <mml:mrow> <mml:msubsup> <mml:mrow/> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.2</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.17</mml:mn> </mml:mrow> </mml:msubsup> </mml:mrow> </mml:mfenced> </mml:mrow> <mml:mrow> <mml:mi>sys</mml:mi> </mml:mrow> </mml:msub> </mml:math> and energy cutoff <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>E</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>c</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>5.1</mml:mn> <mml:mo>±</mml:mo> <mml:msub> <mml:mrow> <mml:mfenced close=")" open="("> <mml:mrow> <mml:mn>1.6</mml:mn> </mml:mrow> </mml:mfenced> </mml:mrow> <mml:mrow> <mml:mi>stat</mml:mi> </mml:mrow> </mml:msub> <mml:msub> <mml:mrow> <mml:mfenced close=")" open="("> <mml:mrow> <mml:msubsup> <mml:mrow/> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>2.5</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>1.4</mml:mn> </mml:mrow> </mml:msubsup> </mml:mrow> </mml:mfenced> </mml:mrow> <mml:mrow> <mml:mi>sys</mml:mi> </mml:mrow> </mml:msub> </mml:math> TeV, while the intrinsic spectrum of Mrk 501 is better described by a simple power law with index <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>α</mml:mi> <mml:mo>=</mml:mo> <mml:mn>2.61</mml:mn> <mml:mo>±</mml:mo> <mml:msub> <mml:mrow> <mml:mfenced close=")" open="("> <mml:mrow> <mml:mn>0.11</mml:mn> </mml:mrow> </mml:mfenced> </mml:mrow> <mml:mrow> <mml:mi>stat</mml:mi> </mml:mrow> </mml:msub> <mml:msub> <mml:mrow> <mml:mfenced close=")" open="("> <mml:mrow> <mml:msubsup> <mml:mrow/> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.07</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.01</mml:mn> </mml:mrow> </mml:msubsup> </mml:mrow> </mml:mfenced> </mml:mrow> <mml:mrow> <mml:mi>sys</mml:mi> </mml:mrow> </mml:msub> </mml:math> . The maximum energies at which the Mrk 421 and Mrk 501 signals are detected are 9 and 12 TeV, respectively. This makes these some of the highest energy detections to date for spectra averaged over years-long timescales. Since the observation of gamma radiation from blazars provides information about the physical processes that take place in their relativistic jets, it is important to study the broadband spectral energy distributions (SEDs) of these objects. For this purpose, contemporaneous data in the gamma-ray band to the X-ray range, and literature data in the radio to UV range, were used to build time-averaged SEDs that were modeled within a synchrotron-self Compton leptonic scenario.