A bimodal burst energy distribution of a repeating fast radio burst source. (arXiv:2107.08205v2 [astro-ph.HE] UPDATED)

A bimodal burst energy distribution of a repeating fast radio burst source. (arXiv:2107.08205v2 [astro-ph.HE] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Li_D/0/1/0/all/0/1">D. Li</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wang_P/0/1/0/all/0/1">P.Wang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zhu_W/0/1/0/all/0/1">W.W. Zhu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zhang_B/0/1/0/all/0/1">B. Zhang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zhang_X/0/1/0/all/0/1">X.X. Zhang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Duan_R/0/1/0/all/0/1">R. Duan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zhang_Y/0/1/0/all/0/1">Y.K. Zhang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Feng_Y/0/1/0/all/0/1">Y. Feng</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Tang_N/0/1/0/all/0/1">N.Y. Tang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Chatterjee_S/0/1/0/all/0/1">S. Chatterjee</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cordes_J/0/1/0/all/0/1">J.M. Cordes</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cruces_M/0/1/0/all/0/1">M. Cruces</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dai_S/0/1/0/all/0/1">S. Dai</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gajjar_V/0/1/0/all/0/1">V. Gajjar</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hobbs_G/0/1/0/all/0/1">G. Hobbs</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Jin_C/0/1/0/all/0/1">C. Jin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kramer_M/0/1/0/all/0/1">M. Kramer</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lorimer_D/0/1/0/all/0/1">D.R. Lorimer</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Miao_C/0/1/0/all/0/1">C.C. Miao</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Niu_C/0/1/0/all/0/1">C.H. Niu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Niu_J/0/1/0/all/0/1">J.R. Niu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pan_Z/0/1/0/all/0/1">Z.C. Pan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Qian_L/0/1/0/all/0/1">L. Qian</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Spitler_L/0/1/0/all/0/1">L. Spitler</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Werthimer_D/0/1/0/all/0/1">D. Werthimer</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zhang_G/0/1/0/all/0/1">G.Q. Zhang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wang_F/0/1/0/all/0/1">F.Y. Wang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Xie_X/0/1/0/all/0/1">X.Y. Xie</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Yue_Y/0/1/0/all/0/1">Y.L. Yue</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zhang_L/0/1/0/all/0/1">L. Zhang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zhi_Q/0/1/0/all/0/1">Q.J. Zhi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zhu_Y/0/1/0/all/0/1">Y. Zhu</a>

The event rate, energy distribution, and time-domain behaviour of repeating
fast radio bursts (FRBs) contains essential information regarding their
physical nature and central engine, which are as yet unknown. As the first
precisely-localized source, FRB 121102 has been extensively observed and shows
non-Poisson clustering of bursts over time and a power-law energy distribution.
However, the extent of the energy distribution towards the fainter end was not
known. Here we report the detection of 1652 independent bursts with a peak
burst rate of 122~hr^{-1}, in 59.5 hours spanning 47 days. A peak in the
isotropic equivalent energy distribution is found to be ~4.8 x 10^{37} erg at
1.25~GHz, below which the detection of bursts is suppressed. The burst energy
distribution is bimodal, and well characterized by a combination of a
log-normal function and a generalized Cauchy function. The large number of
bursts in hour-long spans allow sensitive periodicity searches between 1 ms and
1000 s. The non-detection of any periodicity or quasi-periodicity poses
challenges for models involving a single rotating compact object. The high
burst rate also implies that FRBs must be generated with a high radiative
efficiency, disfavoring emission mechanisms with large energy requirements or
contrived triggering conditions.

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