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

Journal Article · Thu Jun 01 00:00:00 EDT 2017 · Astrophysical Journal

DOI:https://doi.org/10.3847/1538-4357/AA729E· OSTI ID:22872660

Abeysekara, A. U.; Barber, A. S. ^[1]; Albert, A. ^[2]; Alfaro, R.; Rojas, D. Avila; Becerril, A.; Belmont-Moreno, E. ^[3]; Alvarez, C.; Arceo, R.; Caballero-Mora, K. S. ^[4]; Álvarez, J. D.; Arteaga-Velázquez, J. C. ^[5]; Solares, H. A. Ayala; Brisbois, C. ^[6]; Bautista-Elivar, N. ^[7]; Gonzalez, J. Becerra ^[8]; BenZvi, S. Y. ^[9]; Bernal, A. ^[10]; Braun, J. ^[11]; others, and

---

1. Department of Physics and Astronomy, University of Utah, Salt Lake City, UT (United States)
2. Physics Division, Los Alamos National Laboratory, Los Alamos, NM (United States)
3. Instituto de Física, Universidad Nacional Autónoma de México, Mexico City (Mexico)
4. Universidad Autónoma de Chiapas, Tuxtla Gutiérrez, Chiapas, México (Mexico)
5. Universidad Michoacana de San Nicolás de Hidalgo, Morelia (Mexico)
6. Department of Physics, Michigan Technological University, Houghton, MI (United States)
7. Universidad Politecnica de Pachuca, Pachuca, Hidalgo (Mexico)
8. NASA Goddard Space Flight Center, Greenbelt, MD (United States)
9. Department of Physics and Astronomy, University of Rochester, Rochester, NY (United States)
10. Instituto de Astronomía, Universidad Nacional Autónoma de México, Mexico City (Mexico)
11. 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, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 841; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ALTITUDE
BL LACERTAE OBJECTS
COMPARATIVE EVALUATIONS
CRAB NEBULA
EMISSION
GALAXIES
GAMMA RADIATION
TEV RANGE 01-10