Fast radio bursts(FRBs)are millisecond-duration flashes of Giga-Hertz radio emission.Since Lorimer and his collaborators[1]claimed their discovery in 2007,FRBs have remained one of the hottest fields in astronomy.In this research field,the physical origin,radiation mechanism and ambient environment are three of the key questions that have been unsolved[2,3].Since FRB 20121102A was discovered to occur repeatedly for the first time by the Arecibo radio telescope[4],repeating FRBs have become particularly interesting.In a recent paper[5],repeating FRB 20190520B discovered by the Five-hundred-meter Aperture Spher-ical radio Telescope(FAST)was reported.Following this discovery,further observations of this source by some telescopes such as FAST[5],the Karl G.Jansky Very Large Array[5],the Robert C.Byrd Green Bank Telescope[6],and Parkes[7]showed that:(1)the host galaxy of this FRB is a dwarf galaxy,whose redshift is z=0.241 and dispersion measure(DM)including a possible contribution from the circum-burst environment(DMhost=900+72-111 pc/cm3)is about one order of magnitude larger than the average value of the host galaxies of other FRBs(DMhost～100 pc/cm3);(2)a persistent radio source associated with this FRB was discovered,which is the sec-ond persistent radio source(the first one is FRB 20121102A);and(3)the detected Faraday rotation measure(RM)evolved rapidly and changed its sign from 104 to-1.6×104 rad/m2 in about half a year.

Zigao Dai

Department of Astronomy,University of Science and Technology of China,Hefei 230026,China;School of Astronomy and Space Science,Nanjing University,Nanjing 210093,China

科学通报（英文版）

[1]Zigao Dai-.A repeating fast radio burst with rapidly evolving rotation measure)[J].科学通报（英文版）,2022(15):1517-1518

FRBs,Giga,20121102A,Arecibo,20190520B,Spher,Jansky,DMhost,900+72

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