表題番号：2024Q-016
日付：2025/04/04
研究課題Combined Spectrum and Anisotropy Study of Cosmic Rays from the Vela SNR with CALET
| 研究者所属（当時） | 資格 | 氏名 | |
|---|---|---|---|
| （代表者） | 理工学術院 国際理工学センター（理工学術院） | 教授 | モッツ ホルガー マルティン |
| （連携研究者） | 先進理工学部物理学科 | 学部４年生 | 玉置 功 |
| （連携研究者） | 理工学術院 理工学術院総合研究所 | 主任研究員（研究院准教授） | 赤池 陽水 |
- 研究成果概要
- This project focused on the improvement of previously developed analysis methods for signatures of the nearby Vela supernova remnant (SNR) in high energy electron cosmic rays (CR) measured with the CALET detector on the ISS.
In the TeV energy region, only few nearby and young SNR contribute, and Vela is expected to dominate. A spectral hardening in the TeV region, as well as a dipole flux anisotropy in direction of Vela are the possible signatures of its CR emission.
Detection of such a signature would be the first direct observation of charged CR from an individual astrophysical source, confirming that CR originate from SNRs and likely revealing important information about their acceleration and propagation.
In order to increase the sensitivity of the search, an analysis method combining both signatures was developed. The output of the spectral analysis method is the likelihood ratio between including a term for the contribution of the nearby SNR in the PDF fitted to the event energy distribution, and not including it. The anisotropy analysis algorithm was reformulated to yield also a likelihood ratio, here between the cases of a dipole anisotropy towards Vela and no anisotropy (instead of distributions of the dipole strength for models with/without anisotropy as in the old version). By multiplication of both likelihood ratios, the information of both effects is combined and a higher significance for the contribution of Vela obtained. This algorithm and initial test results were presented at the CALET TIM in September 2024.
The expected sensitivity of CALET to signatures from Vela with this algorithm was evaluated based on simulated event data for various conditions of CR release from the Vela SNR, showing that CALET has a good chance of making a detection with high significance, especially if assuming the increased statistics from future operation until 2030. The results from this study were shown at the JPS spring meeting in March 2025.
Furthermore, simulations to obtain a refined prediction of the direction and energy dependent exposure function for CALET, which is essential for the anisotropy measurement, were conducted. Using this new exposure map, updated sensitivity estimates are being calculated and will be presented at the upcoming ICRC conference in July 2025.
In parallel, studies to refine the underlying CR propagation models were undertaken, introducing machine learning methods to supplement time consuming numerical calculations. Preliminary results on this were shown at the JPS annual meeting in September 2024.