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Title: Constraining the Origin of Local Positrons with HAWC TeV Gamma-Ray Observations of Two Nearby Pulsar Wind Nebulae

Abstract

Cosmic-ray positrons are charged antiparticles that strike Earth's atmosphere isotropically. At energies below several GeV they are produced by cosmic-ray protons interacting with nearby interstellar matter. At higher energies, an unexpected and unexplained excess above the proton-induced background has been detected by several satellites, including PAMELA, AMS-02 and Fermi. Due to energy losses in interstellar magnetic and radiation fields, the highest-energy positrons observed must have originated in our immediate Galactic neighborhood. This excess has been theorized to be originated from nearby astrophysical sources, dark matter, or new modes of cosmic-ray secondary production. Amongst the astrophysical sources, pulsars as Geminga and PSR B0656+14 have been proposed to be contributors to this excess. The HAWC Gamma-Ray Observatory reported the discovery of TeV gamma-ray emission extending several degrees around the positions of Geminga and PSR B0656+14 pulsars. Using the morphological and spectral measurements of these two VHE gamma-ray sources, we determine the diffusion coefficient of electrons escaping them and their contribution to the positron flux measured at Earth. For this assumption of isotropic diffusion, we find that neither of these sources make an appreciable contribution to the locally measured positron flux.

Authors:
 [1];  [2];  [3];  [4];  [3]
  1. Max-Planck-Inst. für Kernphysik, Saupfercheckweg, Heidelberg (Germany)
  2. Max-Planck-Inst. für Kernphysik, Saupfercheckweg, Heidelberg (Germany); Inst. Fizyki Ja˛drowej, Radzikowskiego, Krakow (Poland)
  3. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  4. Inst. Fizyki Ja˛drowej, Radzikowskiego, Krakow (Poland)
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE Laboratory Directed Research and Development (LDRD) Program
Contributing Org.:
HAWC Collaboration
OSTI Identifier:
1565877
Report Number(s):
LA-UR-17-27617
Journal ID: 1824-8039
Grant/Contract Number:  
89233218CNA000001
Resource Type:
Accepted Manuscript
Journal Name:
PoS Proceedings of Science
Additional Journal Information:
Journal Volume: 312; Conference: 7th International Fermi Symposium, Garmisch-Partenkirchen (Germany), 15-20 Oct 2017
Publisher:
SISSA
Country of Publication:
United States
Language:
English
Subject:
Astronomy and Astrophysics

Citation Formats

Lopez-Coto, Ruben, Casanova, Sabrina, Dingus, B., Salesa-Greus, F., and Zhou, H. Constraining the Origin of Local Positrons with HAWC TeV Gamma-Ray Observations of Two Nearby Pulsar Wind Nebulae. United States: N. p., 2017. Web. doi:10.22323/1.312.0011.
Lopez-Coto, Ruben, Casanova, Sabrina, Dingus, B., Salesa-Greus, F., & Zhou, H. Constraining the Origin of Local Positrons with HAWC TeV Gamma-Ray Observations of Two Nearby Pulsar Wind Nebulae. United States. doi:10.22323/1.312.0011.
Lopez-Coto, Ruben, Casanova, Sabrina, Dingus, B., Salesa-Greus, F., and Zhou, H. Tue . "Constraining the Origin of Local Positrons with HAWC TeV Gamma-Ray Observations of Two Nearby Pulsar Wind Nebulae". United States. doi:10.22323/1.312.0011. https://www.osti.gov/servlets/purl/1565877.
@article{osti_1565877,
title = {Constraining the Origin of Local Positrons with HAWC TeV Gamma-Ray Observations of Two Nearby Pulsar Wind Nebulae},
author = {Lopez-Coto, Ruben and Casanova, Sabrina and Dingus, B. and Salesa-Greus, F. and Zhou, H.},
abstractNote = {Cosmic-ray positrons are charged antiparticles that strike Earth's atmosphere isotropically. At energies below several GeV they are produced by cosmic-ray protons interacting with nearby interstellar matter. At higher energies, an unexpected and unexplained excess above the proton-induced background has been detected by several satellites, including PAMELA, AMS-02 and Fermi. Due to energy losses in interstellar magnetic and radiation fields, the highest-energy positrons observed must have originated in our immediate Galactic neighborhood. This excess has been theorized to be originated from nearby astrophysical sources, dark matter, or new modes of cosmic-ray secondary production. Amongst the astrophysical sources, pulsars as Geminga and PSR B0656+14 have been proposed to be contributors to this excess. The HAWC Gamma-Ray Observatory reported the discovery of TeV gamma-ray emission extending several degrees around the positions of Geminga and PSR B0656+14 pulsars. Using the morphological and spectral measurements of these two VHE gamma-ray sources, we determine the diffusion coefficient of electrons escaping them and their contribution to the positron flux measured at Earth. For this assumption of isotropic diffusion, we find that neither of these sources make an appreciable contribution to the locally measured positron flux.},
doi = {10.22323/1.312.0011},
journal = {PoS Proceedings of Science},
number = ,
volume = 312,
place = {United States},
year = {2017},
month = {12}
}

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