A possible observational evidence for θ−2\theta^{-2} angular distribution of opening half-angle of GRB jets

We propose a method to estimate the pseudo jet opening half-angle of GRBs using the spectral peak energy (\Ep)--peak luminosity relation (so called Yonetoku relation) as well as the \Ep--collimation-corrected $\gamma$-ray energy relation (so called Ghirlanda relation). For bursts with known jet break times and redshifts, we compared the pseudo jet opening half-angle with the standard one and found that the differences are within a factor 2. We apply the method to 689 long GRBS. We found that the distribution function of the pseudo jet opening half-angle obeys $f(\theta_j)\propto\theta_j^{-2.2 \pm 0.2}$ with possible cutoffs for $\theta_j 0.3$ although the log-normal fit is also possible. $\theta^{-2}$ distribution is compatible with the structured jet model. From the distribution function we found that the beaming correction for the rate of GRBs is $\sim 340$, which means $\sim 10^{-5}$ yr$^{-1}$ galaxy$^{-1}$ or only one in $10^2$ type Ib/c supernovae. We also found the evolution of the distribution function as a function of the redshift.Comment: 5 pages, 5 figures, submitted to MNRA

モリシマアカシアの全木パルプ化に関する基礎的研究

全木パルプ化に関する基礎的データを蓄積する目的で, モリシマアカシア各部位をパルプ化し, 組織構成要素および紙質と関連づけて研究した。その結果, アカシア樹皮の師部繊維は木繊維より大きい繊維長を持ち, これが全木パルプシートにおける紙力向上に寄与することから, アカシアが全木パルプ化に適した樹種であると推定し得た。なお, 樹皮には製紙に際して悪影響を及ぼすと考えられる要素がほとんど存在しないが, 未さらし全木パルプには易漂白性の褐色斑点が存在する