The Potential of Detecting Radio-flaring Ultracool Dwarfs at L band in the FAST Drift-scan Survey  

作　　者：Jing Tang Chao-Wei Tsai Di Li 

机构地区：[1]CAS Key Laboratory of FAST,National Astronomical Observatories,Chinese Academy of Sciences,Beijing 100101,China [2]University of Chinese Academy of Sciences,Beijing 100049,China [3]NAOC-UKZN Computational Astrophysics Centre,University of Kwa Zulu-Natal,Durban 4000,South Africa

出　　处：《Research in Astronomy and Astrophysics》2022年第6期126-141,共16页天文和天体物理学研究（英文版）

基　　金：supported by the National Natural Science Foundation of China grant Nos. 11988101, 11725313, 11690024, and 11703039;by the International Partnership Program of Chinese Academy of Sciences grant No. 114A11KYSB20160008;by the CAS Strategic Priority Research No. XDB23000000;FAST is operated by the Open Project Program of the Key Laboratory of FAST, Chinese Academy of Sciences。

摘　　要：The Five-hundred-meter Aperture Spherical radio Telescope(FAST)completed its commissioning and began the Commensal Radio Astronomy Fas T Survey(CRAFTS),a multi-year survey to cover 60%of the sky,in 2020.We present predictions for the number of radio-flaring ultracool dwarfs(UCDs)that are likely to be detected by CRAFTS.Based on the observed flaring UCDs from a number of unbiased,targeted radio surveys in the literature,we derive a detection rate of≥3%.Assuming a flat radio spectrumνLν∝ν^(β+1) withβ=-1.0 for UCD flares,we construct a flare luminosity function dN/dL∝L^(-1.96±0.45)(here L=νLν).CRAFTS is found to be sensitive enough for flares from UCDs up to~180 pc.Considering the Galactic thin disk,we carry out a 3D Monte Carlo simulation of the UCD population,which is then fed to mock CRAFTS observations.We estimate that~170 flaring UCDs would be detected through transient searches in circular polarization.Though only marginally sensitive to the scale height of UCDs,the results are very sensitive to the assumed spectral indexβ.Forβfrom 0 to-2.5,the number of expected detections increases dramatically from~20 to~3460.We also contemplate the strategies for following up candidates of flaring UCDs,and discuss the implications of survey results for improving our knowledge of UCD behavior at L band and dynamos.

关 键 词：surveys-(stars:)brown dwarfs-stars flare-stars low-mass-stars magnetic field-radio continuum STARS 

分 类 号：P161[天文地球—天文学] P111.44