Astrophysical and Astrobiological Implications of Gamma-Ray Burst Properties
Astrophysical and Astrobiological Implications of Gamma-Ray Burst Properties
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伽马射线暴特性的天体物理学和天体生物学意义
DOI：
10.1086/338329
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发表时间：
1999
期刊：
影响因子：
--
通讯作者：
J. Craig Wheeler
中科院分区：
文献类型：
--
作者：
J. Scalo;J. Craig Wheeler
结合施密特关于γ射线暴（GRB）的局部宇宙率和平均峰值光度的结果和宇宙星星形成率（SFR）的历史结果，我们给出了星系中每单位蓝色光度的局部GRB率的估计.对于SFR随红移的适度增加，我们发现每单位B光度的GRB率为2.4 × 10-17 hLyr-1。银河系中相应的平均γ射线光度密度为1.6 × 1029 ergs-1 pc-2，总速率为5.5 × 10-7 h yr-1。用这些值研究了一些现象，得出以下结论：（1）超新星速率与各向同性等效伽玛暴速率之比很大：每伽玛暴有1.6000 SNe Ibc，每伽玛暴有1.30000 SNe II。如果不对准直进行修正，就很难认为中子星星或黑洞的形成事件中会有一小部分产生伽玛暴。只有当准直度在ΔΩ/4π ~ 0.01-0.001范围内，初始质量函数的斜率足够陡时，大部分黑洞或磁星形成事件才能产生伽玛暴。(2)没有实质性的准直，伽玛射线暴率很小;有准直，能量输入很小。净效应是，不可能使用这些事件来解释在我们自己和其他星系中观察到的大多数大H I洞。(3)模拟银河系中的伽玛射线暴事件作为一个空间泊松过程，并允许适度增强的星星的形成率，由于出生在一个螺旋臂，我们发现，太阳系的概率暴露在一个通量大到足以融化的陨石球粒在第一个107年的太阳系的历史是微不足道的小，独立的准直效应。考虑到有强有力的证据表明陨石球粒不止一次被熔化，这一点尤其正确。(4)我们计算的概率，行星和卫星的表面已受到照射的伽玛射线暴的注量水平超过所需的DNA改变在一段时间内。向下散射到发生光电吸收的能量会导致电离辐射的传输因子，该因子是大气柱密度的指数函数。即使在非常不透明的大气中，由于二次电子的激发，也有相当一部分伽玛射线暴能量以紫外线的形式传输。对于稀薄大气中的类真核生物（例如，当代火星）或用于厚大气中的UV线曝光（例如，地球），具有生物学意义的事件发生率约为100-500 Gyr-1。然而，由于伽马射线暴的持续时间很短，这些“震动”对突变进化的直接贡献可能是可以忽略的。由于部分消毒和大气化学的长期破坏而产生的进化效应应该更为重要。
Combining results from Schmidt for the local cosmic rate and mean peak luminosity of γ-ray bursts (GRBs) with results on the history of the cosmic star formation rate (SFR), we provide estimates for the local GRB rate per unit blue luminosity in galaxies. For a moderate increase in SFR with redshift, we find a GRB rate per unit B luminosity of 2.4 × 10-17 hLyr-1. The corresponding mean γ-ray luminosity density in the Milky Way is 1.6 × 1029 ergs s-1 pc-2, and the total rate is 5.5 × 10-7 h yr-1. These values are used to examine a number of phenomena with the following conclusions: (1) The ratio of supernova rate to isotropic equivalent GRB rate is large: ≳6000 SNe Ibc per GRB, ≳30,000 SNe II per GRB. With no correction for collimation, it is difficult to maintain that more than a small fraction of neutron star- or black hole-forming events produce GRBs. GRBs could arise in a large fraction of black hole- or magnetar-forming events only with collimation in the range ΔΩ/4π ~ 0.01-0.001 and a steep enough slope of the initial mass function. (2) Without substantial collimation, the GRB rate is small; with collimation, the energy input is small. The net effect is that it is impossible to use these events to account for the majority of large H I holes observed in our own and other galaxies. (3) Modeling the GRB events in the Milky Way as a spatial Poisson process and allowing for modest enhancement in the star formation rate due to birth in a spiral arm, we find that the probability that the solar system was exposed to a fluence large enough to melt the chondrules during the first 107 yr of solar system history is negligibly small, independent of collimation effects. This is especially true considering that there is strong evidence that the chondrules were melted more than once. (4) We calculate the probability that surfaces of planets and satellites have been subjected to irradiation from GRBs at fluence levels exceeding those required for DNA alterations during a given period of time. Downscattering to energies at which photoelectric absorption occurs results in a transmission factor for ionizing radiation that is an exponential function of the atmospheric column density. Even for very opaque atmospheres, a significant fraction of the GRB energy is transmitted as UV lines because of excitation by secondary electrons. For eukaryotic-like organisms in thin atmospheres (e.g., contemporary Mars) or for UV line exposure in thick atmospheres (e.g., Earth), biologically significant events occur at a rate of ~100-500 Gyr-1. The direct contribution of these "jolts" to mutational evolution may, however, be negligible because of the short duration of the GRBs. Evolutionary effects due to partial sterilizations and to longer lived disruptions of atmospheric chemistry should be more important.
影响因子：
3.2
作者：
V. Mannings;A. Boss;S. Russell
通讯作者：
V. Mannings;A. Boss;S. Russell