X-Ray and Ultraviolet Flares on AT Microscopii Observed by AstroSat  

作　　者：A.A.Kuznetsov R.R.Karakotov K.Chandrashekhar D.Banerjee 

机构地区：[1]Institute of Solar-Terrestrial Physics,Irkutsk,664033,Russia [2]Department of Geography,Irkutsk State University,Irkutsk,664033,Russia [3]Rosseland Centre for Solar Physics,University of Oslo,PO Box 1029,Blindern 0315 Oslo,Norway [4]Institute of Theoretical Astrophysics,University of Oslo,PO Box 1029,Blindern 0315 Oslo,Norway [5]Aryabhatta Research Institute of Observational Sciences(ARIES),Manora Peak,Nainital 263002,India [6]Indian Institute of Astrophysics,Sarjapur Main Road,2nd Block,Bangalore,Karnataka 560034,India [7]Center of Excellence in Space Science,IISER Kolkata,Kolkata 741246,India

出　　处：《Research in Astronomy and Astrophysics》2023年第1期60-75,共16页天文和天体物理学研究（英文版）

基　　金：supported by the BRICS Multilateral Research and Development Projects-2016(DST/MRCK/BRICS/Pilot Call1/Superflares/2017);the project“Superflares on stars and the Sun,”the Russian Foundation for Basic Research under Grant 17-52-80064;the Ministry of Science and Higher Education of the Russian Federation;supported by the Research Council of Norway through its Centres of Excellence scheme(project No.262622)。

摘　　要：We present observations of the active M-dwarf binary AT Mic(dM4.5e+dM4.5e)obtained with the orbital observatory Astro Sat.During 20 ks of observations,in the far-ultraviolet(130-180 nm)and soft X-ray(0.3-7 keV)spectral ranges,we detected both quiescent emission and at least five flares on different components of the binary.The X-ray flares were typically longer than and delayed(by 5-6 minutes)with respect to their ultraviolet counterparts,in agreement with the Neupert effect.Using X-ray spectral fits,we estimated the parameters of the emitting plasma.The results indicate the presence of a hot multi-thermal corona with average temperatures in the range of~7-15 MK and emission measure of~(2.9-4.5)×10^(52)cm^(-3);both the temperature and the emission measure increased during the flares.The estimated abundance of heavy elements in the corona of AT Mic is considerably lower than at the Sun(~0.18-0.34 of the solar photospheric value);the coronal abundance increased during the flares due to chromospheric evaporation.The detected flares had the energies of~10^(31)-10^(32)erg;the energy-duration relations indicate the presence of magnetic fields stronger than in typical solar flares.

关 键 词：STARS coronae-stars flare-stars late-type-X-rays STARS ULTRAVIOLET 

分 类 号：P185[天文地球—天文学]