The likely counterpart to γ-ray excess from the northwest region of Arp 220  

作　　者：Yun-Chuan Xiang Jun-Hao Deng Ze-Jun Jiang 

机构地区：[1]Department of Astronomy,Yunnan University,and Key Laboratory of Astroparticle Physics of Yunnan Province,Kunming 650091,China

出　　处：《Research in Astronomy and Astrophysics》2021年第7期171-176,共6页天文和天体物理学研究（英文版）

基　　金：the support for this work from the National Key R&D Program of China under Grant No.2018YFA0404204;the National Natural Science Foundation of China(NSFC U1931113 and U1738211);the Foundations of Yunnan Province(2018IC059 and 2018FY001(-003));the scientific research fund of Yunnan Education Department(2020Y0039)。

摘　　要：The unknown γ-ray excess in the northwest region of Arp 220 was revisited by analyzing~11.8 years of the Fermi Large Area Telescope(Fermi-LAT) data in this study.We found that its photon flux was approximately three times higher than that of the previous study in the 0.2-100 GeV band,and the corresponding significance level ~8.15σ was approximately four times higher than before.The light curves of 15 and 45 time bins from the whole time all showed two active periods,and the variability of the second period was more significant than that of the first period.The spectral indices from the two active periods were not statistically different and were close to the range of γ-ray flat-spectrum radio quasars observed by Fermi-LAT.Because the position of CRATES J153246+234400 was consistent with the best-fit position of our analysis,we suggest that CRATES J153246+234400 is more likely a γ-ray counterpart for the variational region.For Arp 220,there was no significant variability in the γ-ray emission.

关 键 词：flat spectrum radio quasar:individual(CRATES J153246+234400) QUASARS γ-ray emission 

分 类 号：P157.7[天文地球—天文学]