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1. Observation of the Crab Nebula with the HAWC Gamma-Ray Observatory

Author

Abeysekara, AU, Albert, A, Alfaro, R, Alvarez, C, Álvarez, JD, Arceo, R, Arteaga-Velázquez, JC, Solares, HA Ayala, Barber, AS, Bautista-Elivar, N, Becerril, A, Belmont-Moreno, E, BenZvi, SY, Berley, D, Braun, J, Brisbois, C, Caballero-Mora, KS, Capistrán, T, Carramiñana, A, Casanova, S, Castillo, M, Cotti, U, Cotzomi, J, de León, S Coutiño, de la Fuente, E, De León, C, DeYoung, T, Dingus, BL, DuVernois, MA, Díaz-Vélez, JC, Ellsworth, RW, Fiorino, DW, Fraija, N, García-González, JA, Gerhardt, M, Munöz, A González, González, MM, Goodman, JA, Hampel-Arias, Z, Harding, JP, Hernandez, S, Hernandez-Almada, A, Hinton, J, Hui, CM, Hüntemeyer, P, Iriarte, A, Jardin-Blicq, A, Joshi, V, Kaufmann, S, Kieda, D, Lara, A, Lauer, RJ, Lee, WH, Lennarz, D, Vargas, H León, Linnemann, JT, Longinotti, AL, Raya, G Luis, Luna-García, R, López-Coto, R, Malone, K, Marinelli, SS, Martinez, O, Martinez-Castellanos, I, Martínez-Castro, J, Martínez-Huerta, H, Matthews, JA, Miranda-Romagnoli, P, Moreno, E, Mostafá, M, Nellen, L, Newbold, M, Nisa, MU, Noriega-Papaqui, R, Pelayo, R, Pretz, J, Pérez-Pérez, EG, Ren, Z, Rho, CD, Rivière, C, Rosa-González, D, Rosenberg, M, Ruiz-Velasco, E, Salazar, H, Greus, F Salesa, Sandoval, A, Schneider, M, Schoorlemmer, H, Sinnis, G, Smith, AJ, Springer, RW, Surajbali, P, Taboada, I, Tibolla, O, Tollefson, K, Torres, I, Ukwatta, TN, Villaseñor, L, Weisgarber, T, and Westerhoff, S

Subjects
acceleration of particles, gamma rays: general, ISM: individual objects, astro-ph.HE, Astronomical and Space Sciences, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Physical Chemistry (incl. Structural), Astronomy & Astrophysics
Abstract

The Crab Nebula is the brightest TeV gamma-ray source in the sky and has been used for the past 25 years as a reference source in TeV astronomy, for calibration and verification of new TeV instruments. The High Altitude Water Cherenkov Observatory (HAWC), completed in early 2015, has been used to observe the Crab Nebula at high significance across nearly the full spectrum of energies to which HAWC is sensitive. HAWC is unique for its wide field of view, nearly 2 sr at any instant, and its high-energy reach, up to 100 TeV. HAWC's sensitivity improves with the gamma-ray energy. Above ∼1 TeV the sensitivity is driven by the best background rejection and angular resolution ever achieved for a wide-field ground array. We present a time-integrated analysis of the Crab using 507 live days of HAWC data from 2014 November to 2016 June. The spectrum of the Crab is fit to a function of the form φ(E)= φ0(E/E0)-α-β In(E/E0). The data is well fitted with values of α = 2.63 ±0.03, β = 0.15 ±0.03, and log10(φ0cm2s TeV)=-12.60±0.02 when E 0 is fixed at 7 TeV and the fit applies between 1 and 37 TeV. Study of the systematic errors in this HAWC measurement is discussed and estimated to be ±50% in the photon flux between 1 and 37 TeV. Confirmation of the Crab flux serves to establish the HAWC instrument's sensitivity for surveys of the sky. The HAWC all-sky survey will be the deepest survey of the northern sky ever conducted in the multi-TeV band.

Published
2017

2. SEARCH FOR TeV GAMMA-RAY EMISSION FROM POINT-LIKE SOURCES IN THE INNER GALACTIC PLANE WITH A PARTIAL CONFIGURATION OF THE HAWC OBSERVATORY

Author

Abeysekara, AU, Alfaro, R, Alvarez, C, Álvarez, JD, Arceo, R, Arteaga-Velázquez, JC, Solares, HA Ayala, Barber, AS, Baughman, BM, Bautista-Elivar, N, Reyes, AD Becerril, Belmont, E, BenZvi, SY, Bernal, A, Braun, J, Caballero-Mora, KS, Capistrán, T, Carramiñana, A, Casanova, S, Castillo, M, Cotti, U, Cotzomi, J, de León, S Coutińo, de la Fuente, E, De León, C, DeYoung, T, Hernandez, R Diaz, Dingus, BL, DuVernois, MA, Ellsworth, RW, Enriquez-Rivera, O, Fiorino, DW, Fraija, N, Garfias, F, González, MM, Goodman, JA, Gussert, M, Hampel-Arias, Z, Harding, JP, Hernandez, S, Hüntemeyer, P, Hui, CM, Imran, A, Iriarte, A, Karn, P, Kieda, D, Lara, A, Lauer, RJ, Lee, WH, Lennarz, D, Vargas, H León, Linnemann, JT, Longo, M, Raya, G Luis, Malone, K, Marinelli, A, Marinelli, SS, Martinez, H, Martinez, O, Martínez-Castro, J, Matthews, JA, Miranda-Romagnoli, P, Moreno, E, Mostafá, M, Nellen, L, Newbold, M, Noriega-Papaqui, R, Patricelli, B, Pelayo, R, Pérez-Pérez, EG, Pretz, J, Ren, Z, Rivière, C, Rosa-González, D, Salazar, H, Greus, F Salesa, Sandoval, A, Schneider, M, Sinnis, G, Smith, AJ, Woodle, K Sparks, Springer, RW, Taboada, I, Tibolla, O, Tollefson, K, Torres, I, Ukwatta, TN, Villaseñor, L, Vrabel, K, Weisgarber, T, Westerhoff, S, Wisher, IG, Wood, J, Yapici, T, Yodh, GB, Younk, PW, Zaborov, D, Zepeda, A, and Zhou, H

Subjects
astroparticle physics, gamma rays: diffuse background, gamma rays: general, astro-ph.HE, Astronomical and Space Sciences, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Physical Chemistry (incl. Structural), Astronomy & Astrophysics
Abstract

A survey of the inner Galaxy region of Galactic longitude l ∈[+15,+50] and latitude b ∈ [-4, +4] is performed using one-third of the High Altitude Water Cherenkov Observatory, operated during ts construction phase. To address the ambiguities arising from unresolved sources in the data, we use a maximum likelihood technique to identify point source candidates. Ten sources and candidate sources are identified in this analysis. Eight of these are associated with known TeV sources but not all have ifferential fluxes that are compatible with previous measurements. Three sources are detected with significances >5 sigma; after accounting for statistical trials, and are associated with known TeV sources.

Published
2016

3. SEARCH FOR GAMMA-RAYS FROM THE UNUSUALLY BRIGHT GRB 130427A WITH THE HAWC GAMMA-RAY OBSERVATORY

Author

Abeysekara, AU, Alfaro, R, Alvarez, C, Álvarez, JD, Arceo, R, Arteaga-Velázquez, JC, Solares, HA Ayala, Barber, AS, Baughman, BM, Bautista-Elivar, N, BenZvi, SY, Rosales, M Bonilla, Braun, J, Caballero-Mora, KS, Carramiñana, A, Castillo, M, Cotti, U, Cotzomi, J, de la Fuente, E, De León, C, DeYoung, T, Hernandez, R Diaz, Dingus, BL, DuVernois, MA, Ellsworth, RW, Fiorino, DW, Fraija, N, Galindo, A, Garfias, F, González, MM, Goodman, JA, Gussert, M, Hampel-Arias, Z, Harding, JP, Hüntemeyer, P, Hui, CM, Imran, A, Iriarte, A, Karn, P, Kieda, D, Kunde, GJ, Lara, A, Lauer, RJ, Lee, WH, Lennarz, D, Vargas, H León, Linnemann, JT, Longo, M, Luna-García, R, Malone, K, Marinelli, A, Marinelli, SS, Martinez, H, Martinez, O, Martínez-Castro, J, Matthews, JAJ, Torres, E Mendoza, Miranda-Romagnoli, P, Moreno, E, Mostafá, M, Nellen, L, Newbold, M, Noriega-Papaqui, R, Oceguera-Becerra, TO, Patricelli, B, Pelayo, R, Pérez-Pérez, EG, Pretz, J, Rivière, C, Rosa-González, D, Salazar, H, Greus, F Salesa, Sandoval, A, Schneider, M, Sinnis, G, Smith, AJ, Woodle, K Sparks, Springer, RW, Taboada, I, Tollefson, K, Torres, I, Ukwatta, TN, Villaseñor, L, Weisgarber, T, Westerhoff, S, Wisher, IG, Wood, J, Yodh, GB, Younk, PW, Zaborov, D, Zepeda, A, and Zhou, and H

Subjects
gamma-ray burst: individual, gamma rays: general, astro-ph.HE, Astronomical and Space Sciences, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Physical Chemistry (incl. Structural), Astronomy & Astrophysics
Abstract

The first limits on the prompt emission from the long gamma-ray burst (GRB) 130427A in the >100 GeV energy band are reported. GRB 130427A was the most powerful burst ever detected with a redshift z ≲ 0.5 and featured the longest lasting emission above 100 MeV. The energy spectrum extends at least up to 95 GeV, clearly in the range observable by the High Altitude Water Cherenkov (HAWC) Gamma-Ray Observatory, a new extensive air shower detector currently under construction in central Mexico. The burst occurred under unfavorable observation conditions, low in the sky and when HAWC was running 10% of the final detector. Based on the observed light curve at MeV-GeV energies, eight different time periods have been searched for prompt and delayed emission from this GRB. In all cases, no statistically significant excess of counts has been found and upper limits have been placed. It is shown that a similar GRB close to zenith would be easily detected by the full HAWC detector, which will be completed soon. The detection rate of the full HAWC detector may be as high as one to two GRBs per year. A detection could provide important information regarding the high energy processes at work and the observation of a possible cut-off beyond the Fermi Large Area Telescope energy range could be the signature of gamma-ray absorption, either in the GRB or along the line of sight due to the extragalactic background light.

Published
2015

4. Sensitivity of HAWC to high-mass dark matter annihilations

Author

Abeysekara, AU, Alfaro, R, Alvarez, C, Álvarez, JD, Arceo, R, Arteaga-Velázquez, JC, Solares, HA Ayala, Barber, AS, Baughman, BM, Bautista-Elivar, N, Gonzalez, J Becerra, Belmont, E, BenZvi, SY, Berley, D, Rosales, M Bonilla, Braun, J, Caballero-Lopez, RA, Caballero-Mora, KS, Carramiñana, A, Castillo, M, Cotti, U, Cotzomi, J, de la Fuente, E, De León, C, DeYoung, T, Hernandez, R Diaz, Diaz-Cruz, L, Díaz-Vélez, JC, Dingus, BL, DuVernois, MA, Ellsworth, RW, Fiorino, DW, Fraija, N, Galindo, A, Garfias, F, González, MM, Goodman, JA, Grabski, V, Gussert, M, Hampel-Arias, Z, Harding, JP, Hui, CM, Hüntemeyer, P, Imran, A, Iriarte, A, Karn, P, Kieda, D, Kunde, GJ, Lara, A, Lauer, RJ, Lee, WH, Lennarz, D, Vargas, H León, Linares, EC, Linnemann, JT, Longo, M, Luna-Garcia, R, Marinelli, A, Martinez, H, Martinez, O, Martínez-Castro, J, Matthews, JAJ, McEnery, J, Torres, E Mendoza, Miranda-Romagnoli, P, Moreno, E, Mostafá, M, Nellen, L, Newbold, M, Noriega-Papaqui, R, Oceguera-Becerra, T, Patricelli, B, Pelayo, R, Pérez-Pérez, EG, Pretz, J, Rivière, C, Rosa-González, D, Ryan, J, Salazar, H, Salesa, F, Sanchez, FE, Sandoval, A, Schneider, M, Silich, S, Sinnis, G, Smith, AJ, Woodle, K Sparks, Springer, RW, Taboada, I, Toale, PA, Tollefson, K, Torres, I, Ukwatta, TN, Villaseñor, L, Weisgarber, T, Westerhoff, S, Wisher, IG, Wood, J, Yodh, GB, and Younk, PW

Subjects
astro-ph.HE, astro-ph.CO, hep-ph, Astronomical and Space Sciences, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Quantum Physics, Nuclear & Particles Physics
Abstract

The High Altitude Water Cherenkov (HAWC) observatory is a wide field-of-view detector sensitive to gamma rays of 100 GeV to a few hundred TeV. Located in central Mexico at 19° North latitude and 4100 m above sea level, HAWC will observe gamma rays and cosmic rays with an array of water Cherenkov detectors. The full HAWC array is scheduled to be operational in Spring 2015. In this paper, we study the HAWC sensitivity to the gamma-ray signatures of high-mass (multi-TeV) dark matter annihilation. The HAWC observatory will be sensitive to diverse searches for dark matter annihilation, including annihilation from extended dark matter sources, the diffuse gamma-ray emission from dark matter annihilation, and gamma-ray emission from nonluminous dark matter subhalos. Here we consider the HAWC sensitivity to a subset of these sources, including dwarf galaxies, the M31 galaxy, the Virgo cluster, and the Galactic center. We simulate the HAWC response to gamma rays from these sources in several well-motivated dark matter annihilation channels. If no gamma-ray excess is observed, we show the limits HAWC can place on the dark matter cross section from these sources. In particular, in the case of dark matter annihilation into gauge bosons, HAWC will be able to detect a narrow range of dark matter masses to cross sections below thermal. HAWC should also be sensitive to nonthermal cross sections for masses up to nearly 1000 TeV. The constraints placed by HAWC on the dark matter cross section from known sources should be competitive with current limits in the mass range where HAWC has similar sensitivity. HAWC can additionally explore higher dark matter masses than are currently constrained.

Published
2014

5. OBSERVATION OF SMALL-SCALE ANISOTROPY IN THE ARRIVAL DIRECTION DISTRIBUTION OF TeV COSMIC RAYS WITH HAWC

Author

Abeysekara, AU, Alfaro, R, Alvarez, C, Álvarez, JD, Arceo, R, Arteaga-Velázquez, JC, Solares, HA Ayala, Barber, AS, Baughman, BM, Bautista-Elivar, N, Belmont, E, BenZvi, SY, Berley, D, Rosales, M Bonilla, Braun, J, Caballero-Mora, KS, Carramiñana, A, Castillo, M, Cotti, U, Cotzomi, J, de la Fuente, E, De León, C, DeYoung, T, Hernandez, R Diaz, Díaz-Vélez, JC, Dingus, BL, DuVernois, MA, Ellsworth, RW, Fiorino, DW, Fraija, N, Galindo, A, Garfias, F, González, MM, Goodman, JA, Gussert, M, Hampel-Arias, Z, Harding, JP, Hüntemeyer, P, Hui, CM, Imran, A, Iriarte, A, Karn, P, Kieda, D, Kunde, GJ, Lara, A, Lauer, RJ, Lee, WH, Lennarz, D, Vargas, H León, Linnemann, JT, Longo, M, Luna-García, R, Malone, K, Marinelli, A, Marinelli, SS, Martinez, H, Martinez, O, Martínez-Castro, J, Matthews, JAJ, McEnery, J, Torres, E Mendoza, Miranda-Romagnoli, P, Moreno, E, Mostafá, M, Nellen, L, Newbold, M, Noriega-Papaqui, R, Oceguera-Becerra, T, Patricelli, B, Pelayo, R, Pérez-Pérez, EG, Pretz, J, Rivière, C, Rosa-González, D, Ruiz-Velasco, E, Ryan, J, Salazar, H, Greus, F Salesa, Sandoval, A, Schneider, M, Sinnis, G, Smith, AJ, Woodle, K Sparks, Springer, RW, Taboada, I, Toale, PA, Tollefson, K, Torres, I, Ukwatta, TN, Villaseñor, L, Weisgarber, T, Westerhoff, S, Wisher, IG, Wood, J, Yodh, GB, Younk, PW, Zaborov, D, Zepeda, A, and Zhou, and H

Subjects
Astroparticle physics, Cosmic rays, astroparticle physics, cosmic rays, astro-ph.HE, Astronomical and Space Sciences, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Physical Chemistry (incl. Structural), Astronomy & Astrophysics
Abstract

The High-Altitude Water Cherenkov (HAWC) Observatory is sensitive to gamma rays and charged cosmic rays at TeV energies. The detector is still under construction, but data acquisition with the partially deployed detector started in 2013. An analysis of the cosmic-ray arrival direction distribution based on 4.9 × 1010 events recorded between 2013 June and 2014 February shows anisotropy at the 10-4 level on angular scales of about 10°. The HAWC cosmic-ray sky map exhibits three regions of significantly enhanced cosmic-ray flux; two of these regions were first reported by the Milagro experiment. A third region coincides with an excess recently reported by the ARGO-YBJ experiment. An angular power spectrum analysis of the sky shows that all terms up to l = 15 contribute significantly to the excesses.

Published
2014

6. Sensitivity of the high altitude water Cherenkov detector to sources of multi-TeV gamma rays

Author

Abeysekara, AU, Alfaro, R, Alvarez, C, Álvarez, JD, Arceo, R, Arteaga-Velázquez, JC, Solares, HA Ayala, Barber, AS, Baughman, BM, Bautista-Elivar, N, Belmont, E, BenZvi, SY, Berley, D, Rosales, M Bonilla, Braun, J, Caballero-Lopez, RA, Carramiñana, A, Castillo, M, Cotti, U, Cotzomi, J, de la Fuente, E, De León, C, DeYoung, T, Hernandez, R Diaz, Diaz-Velez, JC, Dingus, BL, DuVernois, MA, Ellsworth, RW, Fernandez, A, Fiorino, DW, Fraija, N, Galindo, A, Garcia-Luna, JL, Garcia-Torales, G, Garfias, F, González, LX, González, MM, Goodman, JA, Grabski, V, Gussert, M, Hampel-Arias, Z, Hui, CM, Hüntemeyer, P, Imran, A, Iriarte, A, Karn, P, Kieda, D, Kunde, GJ, Lara, A, Lauer, RJ, Lee, WH, Lennarz, D, Vargas, H León, Linares, EC, Linnemann, JT, Longo, M, Luna-García, R, Marinelli, A, Martinez, O, Martínez-Castro, J, Matthews, JAJ, Miranda-Romagnoli, P, Moreno, E, Mostafá, M, Nava, J, Nellen, L, Newbold, M, Noriega-Papaqui, R, Oceguera-Becerra, T, Patricelli, B, Pelayo, R, Pérez-Pérez, EG, Pretz, J, Rivière, C, Ryan, J, Rosa-González, D, Salazar, H, Salesa, F, Sandoval, A, Santos, E, Schneider, M, Silich, S, Sinnis, G, Smith, AJ, Sparks, K, Springer, RW, Taboada, I, Toale, PA, Tollefson, K, Torres, I, Ukwatta, TN, Villaseñor, L, Weisgarber, T, Westerhoff, S, Wisher, IG, Wood, J, Yodh, GB, Younk, PW, Zaborov, D, and Zepeda, A

Subjects
TeV gamma-ray astronomy, Water cherenkov, Cosmic ray, astro-ph.HE, Astronomical and Space Sciences, Atomic, Molecular, Nuclear, Particle and Plasma Physics, Nuclear & Particles Physics
Abstract

The High Altitude Water Cherenkov (HAWC) observatory is an array of large water Cherenkov detectors sensitive to gamma rays and hadronic cosmic rays in the energy band between 100 GeV and 100 TeV. The observatory will be used to measure high-energy protons and cosmic rays via detection of the energetic secondary particles reaching the ground when one of these particles interacts in the atmosphere above the detector. HAWC is under construction at a site 4100 meters above sea level on the northern slope of the volcano Sierra Negra, which is located in central Mexico at 19 N latitude. It is scheduled for completion in 2014. In this paper we estimate the sensitivity of the HAWC instrument to point-like and extended sources of gamma rays. The source fluxes are modeled using both unbroken power laws and power laws with exponential cutoffs. HAWC, in one year, is sensitive to point sources with integral power-law spectra as low as 5×10-13 cm-2sec-1 above 2 TeV (approximately 50 mCrab) over 5 sr of the sky. This is a conservative estimate based on simple event parameters and is expected to improve as the data analysis techniques are refined. We discuss known TeV sources and the scientific contributions that HAWC can make to our understanding of particle acceleration in these sources. © 2013 Elsevier B.V. All rights reserved.

Published
2013

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