AstroSat Observations of the Be/X-Ray Binary XTE J1946+274 During 2018 and 2021 Outbursts  

作　　者：Amar Deo Chandra Jayashree Roy P.C.Agrawal 

机构地区：[1]Indian Institute of Science Education and Research Kolkata,Mohanpur 741246,West Bengal,India [2]Inter-University Center for Astronomy and Astrophysics,Post Bag 4,Pune 411007,Maharashtra,India [3]Department of Astronomy and Astrophysics,Tata Institute of Fundamental Research,Homi Bhabha Road,Mumbai 400005,Maharashtra,India

出　　处：《Research in Astronomy and Astrophysics》2023年第4期26-43,共18页天文和天体物理学研究（英文版）

摘　　要：We present the timing and spectral studies of the Be/X-ray binary XTE J1946+274 during its 2018 and 2021 giant outbursts using observations with the SXT and LAXPC instruments on the AstroSat satellite.Unlike the 1998 and 2010 outbursts,where a giant outburst was followed by several low intensity periodic outbursts,the 2018 and 2021 outbursts were single outbursts.The X-ray pulsations are detected over a broad energy band covering 0.5–80 keV from the compact object.We construct the spin evolution history of the pulsar over two decades and find that the pulsar spins-up during the outbursts but switches to spin-down state in the quiescent periods between the outbursts.Energy resolved pulse profiles generated in several bands in 0.5–80 keV show that the pulse shape varies with the energy.The energy spectrum of the pulsar is determined for the 2018 and 2021 outbursts.The best fit spectral models require presence of cyclotron resonant scattering feature at about 43 keV in the energy spectra of both the outbursts.We find indication of possible reversal in the correlation between the cyclotron line energy and luminosity which needs to be ascertained from future observations.Using the best fit spectra the X-ray luminosity of XTE J1946+274 is inferred to be 2.7×10^(37) erg s^(-1) for the 2018 observations and 2.3×10^(37) erg s^(-1) for the 2021 observations.We discuss possible mechanisms which can drive outbursts in this transient Be X-ray binary.

关 键 词：accretion-accretion disks-stars neutron-(stars:)pulsars general-X-rays binaries-stars emission-line-Be-X-rays BURSTS 

分 类 号：P14[天文地球—天体物理]