Spectral properties of the Be/X-ray pulsar 2S 1553-542 during type II outbursts

We present an extended study of the Be/X-ray pulsar 2S 1553-542 during its Type II outbursts. have incorporated \emph{NICER, Swift-XRT, RXTE-PCA, \emph{NuSTAR} and FERMI} observations to carry out detailed phase time resolved spectral analysis source. summarized evidence variability cyclotron feature observed in X-ray continuum source with respect pulse phases by using recent observation 2021 outburst The has been performed considering \emph{RXTE} 2008 pulsar. hardness intensity diagram (HID) obtained which follows distinct branches ratio. Diagonal branch is high state whereas horizontal corresponds low state. transition from diagonal occurs at luminosity $(4.88\pm0.24)\;\times\;10^{37}\;erg\;s^{-1}$. photon-index exhibits a weak positive correlation flux along negative branch. existence two different further reflects possibility accretion states separated critical luminosity. spin-up rate found depend on increase flux.