Daily Monitoring of TeV Gamma-Ray Emission from Mrk 421, Mrk 501, and the Crab Nebula with HAWC
- Department of Physics and Astronomy, University of Utah, Salt Lake City, UT (United States)
- Physics Division, Los Alamos National Laboratory, Los Alamos, NM (United States)
- Instituto de Física, Universidad Nacional Autónoma de México, Mexico City (Mexico)
- Universidad Autónoma de Chiapas, Tuxtla Gutiérrez, Chiapas, México (Mexico)
- Universidad Michoacana de San Nicolás de Hidalgo, Morelia (Mexico)
- Department of Physics, Michigan Technological University, Houghton, MI (United States)
- Universidad Politecnica de Pachuca, Pachuca, Hidalgo (Mexico)
- NASA Goddard Space Flight Center, Greenbelt, MD (United States)
- Department of Physics and Astronomy, University of Rochester, Rochester, NY (United States)
- Instituto de Astronomía, Universidad Nacional Autónoma de México, Mexico City (Mexico)
- Department of Physics, University of Wisconsin-Madison, Madison, WI (United States)
We present results from daily monitoring of gamma-rays in the energy range from ∼0.5 to ∼100 TeV 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 Γ=2.21±0.14{sub stat}±0.20{sub sys} and an exponential cut-off E{sub 0}=5.4±1.1{sub stat}±1.0{sub sys} TeV. For Mrk 501, we find an index Γ=1.60±0.30{sub stat}±0.20{sub sys} and exponential cut-off E{sub 0}=5.7±1.6{sub stat}±1.0{sub sys} 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.
- OSTI ID:
- 22872660
- Journal Information:
- Astrophysical Journal, Vol. 841, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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