论文标题
从附近的耀斑星和定期来源TVLM 513-46546堆叠搜索伽马射线排放
A Stacking Search for Gamma-ray Emission from Nearby Flare Stars and the Periodic Source TVLM 513-46546
论文作者
论文摘要
到目前为止，太阳是伽马射线中唯一检测到的唯一孤立的主序列星，尤其是在强大的耀斑期间。年轻的Ultracool矮人的活性要高得多，因此它们也是合理的伽马射线来源。我们使用Fermi Gamma-ray空间望远镜的近12年数据进行了97个最近的X射线和无线电耀斑星的空间堆栈，以搜索GEV排放。堆叠的残差图没有明显的信号。建模上限表明峰值恒星通量至少低于噪声水平的7倍。我们还分析了快速旋转的无线电恒星TVLM 513-46546的相折叠光曲线，报告了暂定（TS = 30）的脉冲信号，并完善其周期。我们通过分析附近的费米目录源和测试场以及使用不同时期重复分析来检验假阳性信号的可能性。尽管对目录源进行了清晰检测，但仍未发现其他周期性信号，而TVLM 513的TS值则系统地增加到最佳时期。推定的伽马射线信号与光峰几乎是相同的，并且与无线电脉冲的相位差为0.4 +/- 0.05旋转。这些结果表明，从相对论质子向下流向光电活性区域的相对论质子发射。与大气碰撞的质子会产生中性乳头，使其腐烂到伽马射线光子中。这将是对伽马射线中正常的孤立星的首次检测，也是恒星磁层中质子加速的最有力的证据。
So far, the Sun is the only isolated main sequence star detected in gamma-rays, particularly during powerful flares. Young ultracool dwarfs are far more active so they are also plausible gamma-ray sources. We performed a spatial stack of 97 of the nearest X-ray and radio flare stars to search for GeV emission using nearly 12 years of data from the Fermi Gamma-ray Space Telescope. The stacked residual maps showed no significant signal. Modeling the upper limits indicates a peak stellar flux at least a factor of 7 below the noise level. We also analyzed the phase-folded light curve of the rapidly rotating radio star TVLM 513-46546, report a tentative (TS = 30) pulsed signal, and refine its period. We examine the possibility of a false positive signal by analyzing nearby Fermi catalog sources and test fields, and by repeating the analysis using different periods. No other periodic signals are found, despite clear detections of the catalog sources, and the TS value for TVLM 513 increases systematically to the optimal period. The putative gamma-ray signal is nearly in phase with the optical peak, and out of phase with the radio pulses by 0.4 +/- 0.05 rotations. These results argue for emission from relativistic protons streaming down flux tubes towards the photospheric active regions. The protons colliding with the atmosphere create neutral pions that decay into gamma-ray photons. This would be the first detection of a normal, isolated star in gamma-rays, and the strongest evidence yet for proton acceleration in stellar magnetospheres.
