褐矮星的伽马射线通量上限：对暗物质湮灭为长寿命中介子的影响
Gamma-ray flux limits from brown dwarfs: Implications for dark matter annihilating into long-lived mediators
AI总结：
本研究利用13年Fermi-LAT数据对九个邻近褐矮星进行伽马射线搜索，未发现显著信号，并设定通量上限；在暗物质湮灭为长寿命中介子的框架下，当前上限不足以约束暗物质-核子截面，需约9倍灵敏度提升以覆盖更广参数空间。
摘要：
褐矮星（BDs）是连接最小质量主序星与巨型气态行星的天体。本文第一部分，我们在13年的Fermi-LAT数据中，对九个邻近褐矮星方向进行了模型无关的伽马射线信号搜索。我们未发现显著的伽马射线过剩，因此，我们使用分箱似然方法设定了伽马射线通量的95%置信水平上限。本文第二部分，我们在一种为褐矮星中伽马射线产生提出的奇异机制下解释这些界限：如果宇宙的暗物质（DM）由与标准模型具有不可忽略耦合的粒子组成，褐矮星可能通过散射有效积累这些粒子。暗物质粒子最终热化，并可以湮灭为轻的、长寿命的中介子，这些中介子随后在褐矮星外部衰变为光子。在此框架内，当前Fermi-LAT对所选褐矮星伽马射线通量的堆叠上限无法对暗物质-核子散射截面设定界限。伽马射线限值需改进约9倍，才能对低于10 GeV的暗物质质量获得散射截面$σ_{χn}$ $\sim 10^{-36}$ cm$^{2}$的界限。这一改进将覆盖中介子衰变长度和暗物质质量参数空间的更大区域。重现本研究结果的代码和数据可在GitLab上获取：https://gitlab.in2p3.fr/francesca.calore/brown-dwarfs-gamma。
英文摘要：
Brown dwarfs (BDs) are celestial objects representing the link between the least massive main-sequence stars and giant gas planets. In the first part of this article, we perform a model-independent search of a gamma-ray signal from the direction of nine nearby BDs in 13 years of \Fermi-LAT data. We find no significant excess of gamma rays, and we, therefore, set 95\% confidence level upper limits on the gamma-ray flux with a binned-likelihood approach. In the second part of the paper, we interpret these bounds within an exotic mechanism proposed for gamma-ray production in BDs: If the dark matter (DM) of the universe is constituted of particles with non-negligible couplings to the standard model, BDs may efficiently accumulate them through scatterings. DM particles eventually thermalise, and can annihilate into light, long-lived, mediators which later decay into photons outside the BD. Within this framework, the current Fermi-LAT stacked upper limits on the gamma-ray flux of the selected BDs do not enable setting a bound on the DM-nucleon cross-section. An improvement of approximately a factor of 9 in the gamma-ray limits is required to obtain bounds on the scattering cross-section $σ_{χn}$ $\sim 10^{-36}$ cm$^{2}$ for DM masses below 10 GeV. This improvement would cover a larger portion of the parameter space in mediator decay length and DM mass. The code and data to reproduce the results of this study are available on GitLab at \github{https://gitlab.in2p3.fr/francesca.calore/brown-dwarfs-gamma}.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
