Fast Radio Bursts have recently been used to place limits on Einstein's Equivalence Principle via observations of time delays between photons of different radio frequencies by \citet{wei15}. These limits on differential post-Newtonian parameters ($Δγ<2.52\times10^{-8}$) are the best yet achieved but still rely on uncertain assumptions, namely the relative contributions of dispersion and gravitational delays to the observed time delays and the distances to FRBs. Also very recently, the first FRB host galaxy has likely been identified, providing the first redshift-based distance estimate to FRB 150418 \citep{kea16}. Moreover, consistency between the \omegaigm\ estimate from FRB 150418 and \omegaigm~expected from $Λ$CDM models and WMAP observations leads one to conclude that the observed time delay for FRB 150418 is highly dominated by dispersion, with any gravitational delays small contributors. This points to even tighter limits on $Δγ$. In this paper, the technique of \citet{wei15} is applied to FRB 150418 to produce a limit of $Δγ< 1 - 2\times10^{-9}$, approximately an order of magnitude better than previous limits and in line with expectations by \citet{wei15} for what could be achieved if the dispersive delay is separated from other effects. Future substantial improvements in such limits will depend on accurately determining the contribution of individual ionized components to the total observed time delays for FRBs.
Semi-supervised morphological classification of fast radio bursts from the second CHIME/FRB catalogue
Dunlap Institute for Astronomy and Astrophysics, University of Toronto（多伦多大学邓普天文学与天体物理研究所）；David A. Dunlap Department for Astronomy and Astrophysics, University of Toronto（多伦多大学大卫·A·邓普天文学与天体物理系）；Department of Statistical Sciences, University of Toronto（多伦多大学统计科学系）
Four New Fast Radio Bursts Discovered in the Parkes 70-cm Pulsar Survey Archive
我们提出了四个新的快速射电暴发现在搜索的帕克斯70厘米脉冲星调查数据档案分散的单脉冲和爆发。我们用HEIMDALL和FETCH检测和分类算法搜索了0到5000 pc cm $^{-3}$之间的离散度（DM）。发现的所有四个FRB的宽度（$> 50$ ms）明显大于迄今为止检测和编目的几乎所有FRB。大的脉冲宽度不受星际散射或通道内色散拖尾的支配。其中一个FRB的DM为3338 pc cm $^{3}$，是迄今为止对任何FRB测量的最大DM。这也是迄今为止任何射电望远镜探测到的第一批FRB，比Lorimer爆发早了近十年。我们的研究结果表明，脉冲星调查档案仍然是以前未检测到的FRB的重要来源，搜索FRB的时间尺度上延伸超过$\sim 100$ ms可能会发现存在更大的人口的宽脉冲FRB。
Dispersion measures of fast radio burst host galaxies derived from IllustrisTNG simulation
本文计算了快射电爆发（FRB）主星系的色散测度（DM）。基于对几个宿主星系的观测，从IllustrisTNG模拟中选择了一个与观测星系具有相似性质的大样本星系。它们被用来计算主星系DM的分布，重复和非重复的FRB。对于重复的FRB，我们推断DM $ _{\mathrm{host}} $ FRB 121102和FRB 180916通过假设的爆发网站跟踪恒星形成率在宿主星系。对于FRB 121102和FRB 180916，中位DM $_{\mathrm{host}}$分别为$35 (1+z)^{1.08}$和$96(1+z)^{0.83}$ pc cm $^{-3}$。在另一种情况下，对于红移范围$z=0.1-1.5$的非重复FRB，DM $_{\mathrm{host}}$的中值约为$30 - 70$ pc cm $^{-3}$，假设爆发点是双星合并的位置。在这种情况下，可以通过$33(1+z)^{0.84}$ pc cm $^{-3}$计算中值DM $_{\mathrm{host}}$的演变。重复和非重复FRB的DM $_{\mathrm{host}}$的分布可以很好地拟合对数正态函数。我们的结果可用于推断非定域FRB的红移。
