The highest energy HAWC sources are likely leptonic and powered by pulsars
Abstract
The HAWC Collaboration has observed gamma rays at energies above 56 TeV from a collection of nine sources. It has been suggested that this emission could be hadronic in nature, requiring that these systems accelerate cosmic-ray protons or nuclei up to PeV-scale energies. In this paper, we instead show that the spectra of these objects favor a leptonic (inverse Compton) origin for their emission. More specifically, the gamma-ray emission from these objects can be straightforwardly accommodated within a model in which $$\sim \mathcal{O}(10\%)$$ of the host pulsar's spindown power is transferred into the acceleration of electrons and positrons with a power-law spectrum that extends to several hundred TeV or higher. Additionally, the spectral break that is observed among these sources is naturally explained within the context of this simple model, and occurs at the energy where the timescale for energy losses matches the age of the pulsar. In contrast, this spectral feature cannot be straightforwardly accommodated in hadronic scenarios. Furthermore, hadronic models predict that these sources should produce more emission at GeV-scale energies than is observed. In light of these considerations, we conclude that HAWC's highest energy sources should be interpreted as TeV halos or pulsar wind nebulae, which produce their emission through inverse Compton scattering, and are powered by the rotational kinetic energy of their host pulsar.
- Authors:
-
- Univ. of Tokyo (Japan)
- Stockholm Univ. (Sweden). The Oskar Klein Centre for Cosmoparticle Physics
- Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Univ. of Chicago, IL (United States). Kavli Inst. for Cosmological Physics (KICP)
- Publication Date:
- Research Org.:
- Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States)
- Sponsoring Org.:
- USDOE Office of Science (SC), High Energy Physics (HEP); JSPS KAKENHI; Swedish Research Council (SRC); Swedish National Space Agency; European Research Council (ERC)
- OSTI Identifier:
- 1824141
- Report Number(s):
- FERMILAB-PUB-21-019-T; arXiv:2101.11026
Journal ID: ISSN 1475-7516; oai:inspirehep.net:1843005; TRN: US2215651
- Grant/Contract Number:
- AC02-07CH11359; JP 18J20943; 2019-05135; 117/19; 742104
- Resource Type:
- Accepted Manuscript
- Journal Name:
- Journal of Cosmology and Astroparticle Physics
- Additional Journal Information:
- Journal Volume: 2021; Journal Issue: 08; Journal ID: ISSN 1475-7516
- Publisher:
- Institute of Physics (IOP)
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 79 ASTRONOMY AND ASTROPHYSICS; 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
Citation Formats
Sudoh, Takahiro, Linden, Tim, and Hooper, Dan. The highest energy HAWC sources are likely leptonic and powered by pulsars. United States: N. p., 2021.
Web. doi:10.1088/1475-7516/2021/08/010.
Sudoh, Takahiro, Linden, Tim, & Hooper, Dan. The highest energy HAWC sources are likely leptonic and powered by pulsars. United States. https://doi.org/10.1088/1475-7516/2021/08/010
Sudoh, Takahiro, Linden, Tim, and Hooper, Dan. Thu .
"The highest energy HAWC sources are likely leptonic and powered by pulsars". United States. https://doi.org/10.1088/1475-7516/2021/08/010. https://www.osti.gov/servlets/purl/1824141.
@article{osti_1824141,
title = {The highest energy HAWC sources are likely leptonic and powered by pulsars},
author = {Sudoh, Takahiro and Linden, Tim and Hooper, Dan},
abstractNote = {The HAWC Collaboration has observed gamma rays at energies above 56 TeV from a collection of nine sources. It has been suggested that this emission could be hadronic in nature, requiring that these systems accelerate cosmic-ray protons or nuclei up to PeV-scale energies. In this paper, we instead show that the spectra of these objects favor a leptonic (inverse Compton) origin for their emission. More specifically, the gamma-ray emission from these objects can be straightforwardly accommodated within a model in which $\sim \mathcal{O}(10\%)$ of the host pulsar's spindown power is transferred into the acceleration of electrons and positrons with a power-law spectrum that extends to several hundred TeV or higher. Additionally, the spectral break that is observed among these sources is naturally explained within the context of this simple model, and occurs at the energy where the timescale for energy losses matches the age of the pulsar. In contrast, this spectral feature cannot be straightforwardly accommodated in hadronic scenarios. Furthermore, hadronic models predict that these sources should produce more emission at GeV-scale energies than is observed. In light of these considerations, we conclude that HAWC's highest energy sources should be interpreted as TeV halos or pulsar wind nebulae, which produce their emission through inverse Compton scattering, and are powered by the rotational kinetic energy of their host pulsar.},
doi = {10.1088/1475-7516/2021/08/010},
journal = {Journal of Cosmology and Astroparticle Physics},
number = 08,
volume = 2021,
place = {United States},
year = {Thu Aug 05 00:00:00 EDT 2021},
month = {Thu Aug 05 00:00:00 EDT 2021}
}
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