English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

We present timing and spectral results of 2018 outburst of Cepheus X-4,observed twice by AstroSat at luminosity of $2.04 \times 10^{37}$ erg s$^{-1}$and $1.02 \times 10^{37}$ erg s$^{-1}$ respectively. The light curves showedstrong pulsation and co-related X-ray intensity variation in SXT (0.5--8.0 keV)and LAXPC (3--60 keV) energy bands. Spin-period and spin-down rate of thepulsar were determined from two observations as $65.35080\pm0.00014$ s ,$(-2.10\pm0.8)\times10^{-12}$ Hz s$^{-1}$ at an epoch MJD 58301.61850 and$65.35290\pm0.00017$ s, $(-1.6\pm0.8)\times10^{-12}$ Hz s$^{-1}$ for an epochMJD 58307.40211. Pulse-shape studies with AstroSat showed energy and intensitydependent variations. The pulsar showed an overall continuous spin-down, over30 years at an average-rate of $(-2.455\pm0.004)\times10^{-14}$ Hz s$^{-1}$,attributed to propeller-effect in the subsonic-regime of the pulsar, inaddition to variations during its outburst activities. Spectra between 0.7--55keV energy band were well fitted by two continuum models, an absorbedcompTT-model and an absorbed power-law with a Fermi-Dirac cutoff (FD-cutoff)model with a black-body. These were combined with an iron-emission line and acyclotron absorption line. The prominent cyclotron resonance scatteringfeatures with a peak absorption energy of $30.48^{+0.33}_{-0.34}$ keV and$30.68^{+0.45}_{-0.44}$ keV for FD-cutoff-model and $30.46^{+0.32}_{-0.28}$ keVand $30.30^{+0.36}_{-0.34}$ keV for compTT-model were detected during twoAstroSat observations. These when compared with earlier results, showed longterm stability of its average value of $30.23 \pm 0.22$ keV. The pulsar showedpulse-phase as well as luminosity dependent variations in cyclotron-line energyand width and in plasma optical-depth of its spectral continuum.

Studies of Cepheus X-4 during 2018 outburst observed with AstroSat