Abstract

Abstract. Massive stars play an important role in explaining the cosmic ray spectrum below the knee, possibly even up to the ankle, i.e. up to energies of 1015 or 1018.5 eV, respectively. In particular, Supernova Remnants are discussed as one of the main candidates to explain the cosmic ray spectrum. Even before their violent deaths, during the stars' regular life times, cosmic rays can be accelerated in wind environments. High-energy gamma-ray measurements indicate hadronic acceleration binary systems, leading to both periodic gamma-ray emission from binaries like LSI + 60 303 and continuous emission from colliding wind environments like η-Carinae. The detection of neutrinos and photons from hadronic interactions are one of the most promising methods to identify particle acceleration sites. In this paper, future prospects to detect neutrinos from colliding wind environments in massive stars are investigated. In particular, the seven most promising candidates for emission from colliding wind binaries are investigated to provide an estimate of the signal strength. The expected signal of a single source is about a factor of 5–10 below the current IceCube sensitivity and it is therefore not accessible at the moment. What is discussed in addition is future the possibility to measure low-energy neutrino sources with detectors like PINGU and ORCA: the minimum of the atmospheric neutrino flux at around 25 GeV from neutrino oscillations provides an opportunity to reduce the background and increase the significance to searches for GeV–TeV neutrino sources. This paper presents the first idea, detailed studies including the detector's effective areas will be necessary in the future to test the feasibility of such an approach.

Highlights

  • While the sources of high-energy cosmic rays are still not directly identified, the search for neutrinos and photons from cosmic ray interactions in the vicinity of the acceleration environments has made great progress within the past couple of years: 1. The Fermi satellite was able to measure gamma-ray emission from two SNRs, i.e. W44 and IC443, in accordance with hadronic models (Ackermann and The Fermi-LAT collaboration, 2013): Fermi detects gammarays from ∼ 100 MeV up to GeV energies and is sensitive to the low-energy cutoff from the pion induced gamma-ray spectrum at ∼ 200 MeV

  • While the above uncertainties make a detection of a GeVsignal from astrophysical sources difficult, it could still be feasible. This option should be considered for future detection arrays like PINGU, as it may be the only chance to see neutrinos from cosmic ray sources with maximum energies smaller than some TeV

  • For the future, considering the potential of low-energy extensions like PINGU or ORCA, colliding wind binary systems (CWBs) should be certainly be considered as interesting neutrino sources, having the potential to reveal both acceleration properties as well as information about the local hydrogen density

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Summary

Introduction

While the sources of high-energy cosmic rays are still not directly identified, the search for neutrinos and photons from cosmic ray interactions in the vicinity of the acceleration environments has made great progress within the past couple of years: 1. The Fermi satellite was able to measure gamma-ray emission from two SNRs, i.e. W44 and IC443, in accordance with hadronic models (Ackermann and The Fermi-LAT collaboration, 2013): Fermi detects gammarays from ∼ 100 MeV up to GeV energies and is sensitive to the low-energy cutoff from the pion induced gamma-ray spectrum at ∼ 200 MeV. The prominent case of η-Carinae was detected at gamma-ray energies by the Fermi satellite (Abdo and The Fermi-LAT collaboration, 2010), showing both a steep component possibly representing inverse Compton photons (Reimer et al, 2006) and a flat component persisting towards higher energies (Farnier et al, 2011). The latter is a strong indication for hadronic acceleration up to GeV energies.

Colliding wind binaries: neutral secondaries from cosmic ray interactions
Conclusions and outlook

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