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CTAO Simulations for Potential PeVatron Candidates

P. Sharma, C. Dubos, S. R. Patel T. Suomijarvi

Abstract

This paper reports on the capabilities of the Cherenkov Telescope Array Observatory (CTAO) in detecting high-energy gamma-rays that show significant contributions of hadronic origin. We focus on four sources: RX J1713.7-3946, HESS J1731-347, Cassiopeia A, and HAWC J2227+610, which have been previously identified as PeVatron candidates, sources capable of accelerating hadrons to PeV energies. In this study, we perform simulations using Gammapy for each source to obtain flux estimates for CTAO. In case of HAWC J2227+610, we also determined the maximum cut-off energy in the proton distribution detectable by measuring gamma-rays with CTAO. To distinguish between fluxes with different proton cut-off energies we used the Test Statistic (TS) method. Additionally, we used the PeVatron Test Statistic (PTS) metric to demonstrate whether CTAO could confirm or exclude SNRs as PeVatron candidates. Through this study, we found that a minimum of 100 hours of observation time is required to detect flux variations with different cut-offs, with the detection limit being around 600 TeV. Through the PTS study, SNRs Cassiopeia A, RX J1713.7-3946, and HESS J1731-347 were excluded as PeVatron sources, while HAWC J2227+610 remains inconclusive.

CTAO Simulations for Potential PeVatron Candidates

Abstract

This paper reports on the capabilities of the Cherenkov Telescope Array Observatory (CTAO) in detecting high-energy gamma-rays that show significant contributions of hadronic origin. We focus on four sources: RX J1713.7-3946, HESS J1731-347, Cassiopeia A, and HAWC J2227+610, which have been previously identified as PeVatron candidates, sources capable of accelerating hadrons to PeV energies. In this study, we perform simulations using Gammapy for each source to obtain flux estimates for CTAO. In case of HAWC J2227+610, we also determined the maximum cut-off energy in the proton distribution detectable by measuring gamma-rays with CTAO. To distinguish between fluxes with different proton cut-off energies we used the Test Statistic (TS) method. Additionally, we used the PeVatron Test Statistic (PTS) metric to demonstrate whether CTAO could confirm or exclude SNRs as PeVatron candidates. Through this study, we found that a minimum of 100 hours of observation time is required to detect flux variations with different cut-offs, with the detection limit being around 600 TeV. Through the PTS study, SNRs Cassiopeia A, RX J1713.7-3946, and HESS J1731-347 were excluded as PeVatron sources, while HAWC J2227+610 remains inconclusive.
Paper Structure (16 sections, 4 equations, 7 figures, 10 tables)

This paper contains 16 sections, 4 equations, 7 figures, 10 tables.

Table of Contents

  1. Introduction
  2. Selected sources
  3. RX J1713.7-3946
  4. Cassiopeia A
  5. HESS J1731-347
  6. HAWC J2227+610
  7. Simulations
  8. Radiative Models
  9. Source Parameters
  10. Simulations with Gammapy
  11. Results of Simulation
  12. Study of different cut-off values
  13. HAWC J2227+610 simulation parameters
  14. Results of the Cut-off Study
  15. Test for PeVatrons
  16. ...and 1 more sections

Figures (7)

  • Figure 1: CTAO simulated flux for SNR RX J1713.7-3946 (left) and SNR Cassiopeia A (right), with data points (blue) generated by the pion-decay model (orange) using parameters based on MWL analysis (see text).
  • Figure 2: CTAO simulated flux for (left) SNR HESS J1731-347 and (right) SNR HAWC J2227+610, with data points (blue) generated by the pion-decay model (orange) using parameters based on MWL analysis (see text).
  • Figure 3: Naima fit result of SNR RX J1713.7-3946 using different theoretical models (see text).
  • Figure 4: Different simulated CTAO fluxes with varying maximum proton energy. The pion-decay model with $E_{cut,p} = 300, 600,$ and $1000$ TeV are represented by blue, orange, and green curves, respectively. The observed data measurements for the source are also shown in black (see text).
  • Figure 5: The fit results of the different proton energy cut-off models and the simulated data for HAWC J2227+610 generated using proton energy cut-off value = 300 TeV (see text).
  • ...and 2 more figures