快速射电暴脉冲研究进入高统计性时代

FAST helps push the study of fast radio bursts into statistical regimes

快速射电暴(fast radio burst,FRB)是在宇宙空间中发生的持续时标为毫秒量级的射电脉冲信号,瞬时辐射流量峰值可达数十央斯基(Jy),爆发的总能量相当于太阳几天甚至几个月内辐射的总能量.快速射电暴于2007年被Lorimer等人[1]首次发现并报道之后,经历了初期的真实性质疑.

The 2007 discovery of fast radio bursts(FRBs),bright and millisecond-duration astronomical radio pulses,presented to the astronomical community a tantalizing opportunity into the transient Universe.Understanding the origins,mechanisms and applications of FRBs is currently one of the most rapidly evolving sub-fields of astrophysics.Most FRBs originate from far outside the Milky Way and are many orders of magnitude more luminous than other known bursting radio sources,particularly pulsars(neutron stars).The total FRB population now stands at approximately 600 published sources,24 repeaters,and 19 with localized host galaxies.Most FRBs appear to be one-off,only about four percent of the FRBs are now known to repeat.While the volume of observations grows at a breakneck pace,the overarching question of the field remains:“Where do FRBs come from?”Interestingly,FRBs can be hosted in a variety of galaxy types and environments.FRB 20121102 was successfully located in a low-mass and low-metallicity dwarf galaxy,coincident with a persistent radio source.VLBI observations have demonstrated that this source is compact.With the Five-hundred-meter Aperture Spherical radio Telescope(FAST),FRB20121102 has been extensively observed,resulting in the discovery of 1652 independent bursts with a peak burst rate of122 per hour and over three orders of magnitude variation in energy.For the first time,the burst energy distribution can be fully recovered and is found to be bimodal,suggesting that there may be more than one emission mechanisms or emission sites or beam shapes.In contrast to the single power-law energy distribution commonly found for FRBs,a characteristic peak in the burst rate energy distribution is found at 4.8×10^(37) erg.The estimated total isotropic energy,6.4×10^(46) erg,released during the 47-day observational campaign,corresponds to approximately 38% of the available magnetar spin energy.Despite the high burst rate,no periodicity has been found.Higher time-resolution data,sustained monitoring,and better localization from the last 2-3 years have provided a wealth of information and significant discoveries regarding the origin of FRBs.A supremely bright FRB-like burst(FRB20200428)has been detected from a Galactic magnetar SGR 1935+2154 by STARE2 and CHIME/FRB.It provides strong evidence linking magnetars to sources of FRBs.The explosively growing number of FRBs and studies of individual FRBs start to reveal the source and radiation mechanisms of FRBs.Significant breakthroughs rely on the emergence of new observational facilities as well as a growing breadth of expertise joining the field.With ever-growing capabilities of observing facilities and processing power,the FRB sample in the next 5 years will supersede that of radio pulsars from the past half century.We are witnessing the unveiling of a dynamic Universe.