Abstract Details
| Name: md alam Affiliation: IUCAA, Pune Conference ID: ASI2019_277 Title : Absorption dips in Cygnus X-1 Authors and Co-Authors : Md Shah Alam, Jayashree Roy, Dipankar Bhattacharya, A. R. Rao, Ajay Ratheesh, Ajay Vibhute, Sudip Chakraborty, Varun Bhalerao, Chaitrali S. Mulay Abstract Type : Poster Abstract Category : Stars, ISM and Galaxy Abstract : XMM-Newton observed the source for the longest duration between 27 May and 2 June 2016. AstroSat also observed the source for the largest duration up to now, ~ 256 ks from 15 May 2016-18 May 2016. It gives us the opportunity to study the distribution of absorption dips with binary phase. Both XMM-Newton and AstroSat have the capability to observe the source in low energy bands (below 2 keV), it improves the statistic very much as we know that short duration absorption dips in Cygnus X-1 occur due to photoelectric absorption of X-ray photons from accretion disk. We find ~ 227 and ~ 10 dips with XMM-Newton and AstroSat respectively. We detect the absorption dips by studying the increment in hardness ratio during dip time. A peak of the distribution of absorption dips is found to be slightly shifted from zero phase. We establish the clumpy nature of absorber by studying the variation of CvrFrac and log(xi) parameter of ZXIPCF model. During dip time, log(xi) decreases and CvrFrac increases. Decreases in log(xi) (xi=L/nr^2) can be attributed to an increase in density of absorber which is the characteristic of clumpy matter. Spectral properties of both XMM Newton and AstroSat observation are consistent with the low/hard state. Power-law index of all the four XMM-Newton observation is $\sim$ 1.55. Break energy in AstroSat spectrum is at $9.31_{-0.62}^{+0.59}$ keV, as expected. Slopes below and after the break are $1.78_{-0.010}^{+0.010}$ and $1.50_{-0.032}^{+0.030}$, consistent with the system being in the low/hard state. |