2021 Fiscal Year Research-status Report
Combined Spectrum and Anisotropy Study of Cosmic Rays from the Vela SNR with CALET
| Project/Area Number |
21K03604
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| Research Institution | Waseda University |
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Principal Investigator |
Motz Holger 早稲田大学, 理工学術院, 准教授(任期付) (30647904)
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| Project Period (FY) |
2021-04-01 – 2024-03-31
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| Keywords | High Energy Cosmic Rays / Vela Supernova Remnant / Cosmic Ray Anisotropy / Cosmic Ray Propagation |
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| Outline of Annual Research Achievements |
Initially, as a benchmark point for the further studies, limits and best-fit values for the total energy of electron cosmic ray emission from the Vela supernova remnant have been calculated based on a standard binned analysis method and for generic emission scenarios (delayed instantaneous release, constant release for a duration). These results were shown at ICRC2021 and published in the proceedings.
Noticing the dependence of the predictions on the cosmic-ray propagation conditions, the underlying propagation models were improved by optimizing the parameters used in the numerical DRAGON calculation of the nuclei spectra in a random walk, until a model explaining the measured nuclei spectra up to oxygen with a common injection spectrum for all nuclei was found. This model explains the differences in the measured nuclei spectra by propagation effects only, without the need for species-specific acceleration mechanisms. Focusing on such well supported propagation conditions allows for more concrete predictions of the spectral and anisotropy signal from Vela, but the model is also useful in other areas such as indirect dark matter search with CALET, and has been first presented in this context.
As planned, an unbinned likelihood analysis method for the electron spectrum has been developed, which can identify a potential spectral hardening in the TeV-region based on the few expected events with high significance, according to simulations. Such a hardening could be considered a spectral signature from the Vela SNR, which would be further supported by an anisotropy signature.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
Compared to the schedule in the research plan, more focus was put on and more progress made in improving the underlying propagation model, delaying further study of more detailed emission scenarios for the Vela SNR. However, by reducing the number of propagation scenarios that have to be studied, more concrete predictions and faster progress is expected in the future.
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| Strategy for Future Research Activity |
It is planned to combine the unbinned likelihood analysis method for anisotropy (explained in the research plan) with the newly developed unbinned likelihood method for the spectrum. The sensitivity of the combined likelihood method to the different scenarios of cosmic-ray flux from Vela is then to be studied through extensive simulations. In this process, also the study of more sophisticated emission scenarios is foreseen.
Still, further improvement and validation of the propagation model, in order to explain also the antiproton spectrum data, and that of nuclei up to iron and nickel, will also be undertaken.
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| Causes of Carryover |
30 yen is a too small amount to buy any items meaningful to the project. Merged with the next fiscal year's budget it can be spent according to the plan.
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