Title

First HAWC observations of the Sun constrain steady TeV gamma-ray emission

Authors

A. Albert, Los Alamos National Laboratory
R. Alfaro, Universidad Nacional Autónoma de México
C. Alvarez, Universidad Autónoma de Chiapas
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, Pennsylvania State University
E. Belmont-Moreno, Universidad Nacional Autónoma de México
S. Y. Benzvi, University of Rochester
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
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
S. Dichiara, Universidad Nacional Autónoma de México
B. L. Dingus, Los Alamos National Laboratory
M. A. Duvernois, University of Wisconsin-Madison
J. C. Díaz-Vélez, Universidad de Guadalajara
K. Engel, University of Maryland
O. Enríquez-Rivera, Universidad Nacional Autónoma de México
C. Espinoza, Universidad Nacional Autónoma de México
H. Fleischhack, Michigan Technological University
N. Fraija, Universidad Nacional Autónoma de México
J. A. García-González, Universidad Nacional Autónoma de México
F. Garfias, Universidad Nacional Autónoma de México
M. M. González, Universidad Nacional Autónoma de México
J. A. Goodman, University of Maryland

Document Type

Article

Publication Date

12-15-2018

Abstract

© 2018 American Physical Society. Steady gamma-ray emission up to at least 200 GeV has been detected from the solar disk in the Fermi-LAT data, with the brightest, hardest emission occurring during solar minimum. The likely cause is hadronic cosmic rays undergoing collisions in the Sun's atmosphere after being redirected from ingoing to outgoing in magnetic fields, though the exact mechanism is not understood. An important new test of the gamma-ray production mechanism will follow from observations at higher energies. Only the High Altitude Water Cherenkov (HAWC) Observatory has the required sensitivity to effectively probe the Sun in the TeV range. Using 3 years of HAWC data from November 2014 to December 2017, just prior to the solar minimum, we search for 1-100 TeV gamma rays from the solar disk. No evidence of a signal is observed, and we set strong upper limits on the flux at a few 10-12 TeV-1 cm-2 s-1 at 1 TeV. Our limit, which is the most constraining result on TeV gamma rays from the Sun, is ∼10% of the theoretical maximum flux (based on a model where all incoming cosmic rays produce outgoing photons), which in turn is comparable to the Fermi-LAT data near 100 GeV. The prospects for a first TeV detection of the Sun by HAWC are especially high during the solar minimum, which began in early 2018.

Publication Title

Physical Review D

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