The fast blue optical transients(FBOTs)are a new population of extragalactic transients of unclear physical origin.A variety of mechanisms has been proposed including failed supernova explosion,shock interaction with a dense medium,young magnetar,accretion onto a compact object and stellar tidal disruption event,but none is conclusive.Here we report the discovery of a possible X-ray quasi-periodicity signal with a period of～250 s(at a significance level of 99.76％)in the brightest FBOT AT2018cow through the analysis of XMM-Newton/PN data.The signal is independently detected at the same frequency in the average power density spectrum from data taken from the Swift telescope,with observations covering from 6 to 37 days after the optical discovery,though the significance level is lower(94.26％).This suggests that the quasi-periodic oscillation(QPO)frequency may be stable over at least 1.1×104 cycles.Assuming the～250 s QPO to be a scaled-down analog of that typically seen in stellar mass black holes,a black hole mass of～103-105 solar masses could be inferred.The overall X-ray luminosity evolution could be modeled with a stellar tidal disruption by a black hole of～104 solar masses,providing a viable mechanism to produce AT2018cow.Our findings suggest that other bright FBOTs may also harbor intermediate-mass black holes.

Wenjie Zhang;Xinwen Shu;Jin-Hong Chen;Luming Sun;Rong-Feng Shen;Lian Tao;Chun Chen;Ning Jiang;Liming Dou;Ying Qin;Xue-Guang Zhang;Liang Zhang;Jinlu Qu;Tinggui Wang

Department of Physics,Anhui Normal University,Wuhu 241002,China;School of Physics and Astronomy,Sun Yat-Sen University,Zhuhai 519082 China;Key Laboratory of Particle Astrophysics,Institute of High Energy Physics,Chinese Academy of Science,Beijing 100049,China;CAS Key Laboratory for Researches in Galaxies and Cosmology,Department of Astronomy,University of Science and Technology of China,Hefei 230026,China;Department of Astronomy,Guangzhou University,Guangzhou 510006,China;School of Physics and Technology,Nanjing Normal University,Nanjing 210023,China

天文和天体物理学研究

[1]Wenjie Zhang;Xinwen Shu;Jin-Hong Chen;Luming Sun;Rong-Feng Shen;Lian Tao;Chun Chen;Ning Jiang;Liming Dou;Ying Qin;Xue-Guang Zhang;Liang Zhang;Jinlu Qu;Tinggui Wang-.A Possible 250 s X-Ray Quasi-periodicity in the Fast Blue Optical Transient AT2018cow)[J].天文和天体物理学研究,2022(12):299-310

AT2018cow,FBOTs,magnetar,FBOT

Possible,Ray,Quasi,periodicity,Fast,Blue,Optical,Transient,fast,blue,optical,transients,are,new,population,extragalactic,unclear,physical,origin,variety,mechanisms,has,been,proposed,including,failed,supernova,explosion,shock,interaction,dense,medium,young,accretion,onto,compact,object,stellar,tidal,disruption,event,but,none,conclusive,Here,report,discovery,possible,ray,quasi,signal,significance,level,brightest,through,analysis,XMM,Newton,PN,data,independently,detected,same,frequency,average,power,density,spectrum,from,taken,Swift,telescope,observations,covering,days,after,though,lower,This,suggests,that,oscillation,QPO,may,stable,least,cycles,Assuming,scaled,down,analog,typically,seen,black,holes,solar,masses,could,inferred,overall,luminosity,evolution,modeled,by,providing,viable,produce,Our,findings,other,also,harbor,intermediate

0.60279