Daily Monitoring of TeV Gamma-Ray Emission from Mrk 421, Mrk 501, and the Crab Nebula with HAWC

Authors

A. U. Abeysekara, The University of Utah
A. Albert, Los Alamos National Laboratory
R. Alfaro, Universidad Nacional Autónoma de México
C. Alvarez, Universidad Autónoma de Chiapas
J. D. Álvarez, Universidad Michoacana de San Nicolás de Hidalgo
R. Arceo, Universidad Autónoma de Chiapas
J. C. Arteaga-Velázquez, Universidad Michoacana de San Nicolás de Hidalgo
D. Avila Rojas, Universidad Nacional Autónoma de México
H. A. Ayala Solares, Michigan Technological University
A. S. Barber, The University of Utah
N. Bautista-Elivar, Universidad Politécnica de Pachuca
J. Becerra Gonzalez, NASA Goddard Space Flight Center
A. Becerril, Universidad Nacional Autónoma de México
E. Belmont-Moreno, Universidad Nacional Autónoma de México
S. Y. Benzvi, University of Rochester
A. Bernal, Universidad Nacional Autónoma de México
J. Braun, University of Wisconsin-Madison
C. Brisbois, Michigan Technological University
K. S. Caballero-Mora, Universidad Autónoma de Chiapas
T. Capistrán, Instituto Nacional de Astrofisica Optica y Electronica
A. Carramiñana, Instituto Nacional de Astrofisica Optica y Electronica
S. Casanova, Henryk Niewodniczanski Institute of Nuclear Physics of the Polish Academy of Sciences
M. Castillo, Universidad Michoacana de San Nicolás de Hidalgo
U. Cotti, Universidad Michoacana de San Nicolás de Hidalgo
J. Cotzomi, Benemerita Universidad Autonoma de Puebla
S. Coutiño De León, Instituto Nacional de Astrofisica Optica y Electronica
C. De León, Benemerita Universidad Autonoma de Puebla
E. De La Fuente, Universidad de Guadalajara
R. Diaz Hernandez, Instituto Nacional de Astrofisica Optica y Electronica
B. L. Dingus, Los Alamos National Laboratory
M. A. Duvernois, University of Wisconsin-Madison
J. C. Díaz-Vélez, Universidad de Guadalajara

Document Type

Article

Publication Date

6-1-2017

Abstract

© 2017. The American Astronomical Society. All rights reserved. We present results from daily monitoring of gamma-rays in the energy range from∼0.5 to ∼100TeV with the first 17 months of data from the High Altitude Water Cherenkov (HAWC) Observatory. Its wide field of view of 2 steradians and duty cycle of > 95% are unique features compared to other TeV observatories that allow us to observe every source that transits over HAWC for up to ∼6 hr each sidereal day. This regular sampling yields unprecedented light curves from unbiased measurements that are independent of seasons or weather conditions. For the Crab Nebula as a reference source, we find no variability in the TeV band. Our main focus is the study of the TeV blazars Markarian (Mrk) 421 and Mrk 501. A spectral fit for Mrk 421 yields a power-law index G = 2.21 0.14 0.20 stat sys and an exponential cut-off E0 stat sys = 5.4 1.1 1.0 TeV. For Mrk 501, we find an index G = 1.60 0.30 0.20 stat sys and exponential cut-off E0 stat sys = 5.7 1.6 1.0 TeV. The light curves for both sources show clear variability and a Bayesian analysis is applied to identify changes between flux states. The highest per-transit fluxes observed from Mrk 421 exceed the Crab Nebula flux by a factor of approximately five. For Mrk 501, several transits show fluxes in excess of three times the Crab Nebula flux. In a comparison to lower energy gamma-ray and X-ray monitoring data with comparable sampling, we cannot identify clear counterparts for the most significant flaring features observed by HAWC.

Publication Title

Astrophysical Journal

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