| Name: | Abhay Kumar |
| Affiliation: | Physical Research Laboratory |
| Conference ID : | ASI2024_60 |
| Title : | Hard X-ray spectro-polarimetric study of black hole binary Cygnus X-1 and related instrumentation |
| Authors : | Abhay kumar, Santosh Vadawale, Tanmoy Chattopadhyay, A R Rao, Dipankar Bhattacharya |
| Authors Affiliation: | 1 Abhay Kumar, Santosh Vadawale Physical Research Laboratory Thaltej, Ahmedabad, Gujarat 380009, India
2 Tanmoy Chattopadhyay Kavli Institute of Particle Astrophysics and Cosmology, Stanford University 452 Lomita Mall, Stanford, CA 94305, US
3 A R Rao, Dipankar Bhattacharya Inter-University Center for Astronomy and Astrophysics Pune, Maharashtra-411007, India
4 Dipankar Bhattacharya Department of Physics, Ashoka University Rai, Sonipat, Haryana-131029, India |
| Mode of Presentation: | Oral |
| Abstract Category : | Thesis |
| Abstract : | Cygnus X-1 is a galactic black hole binary comprising a black hole of mass ~21 solar mass that accretes from the companion supergiant star with a mass of ~40 solar mass. Its brightness and proximity (~2.22 kpc) have made it an obvious choice of study by different instruments. Based on spectroscopy and timing, the typical geometry of the environment surrounding the black hole is an accretion disc, hot cloud of the electron above the disc called corona, and the bipolar outflow in the form of jet. However, timing and spectroscopic results can be explained with different models of the source geometry. To break this degeneracy, polarisation study in broad energy range is important, which gives two additional observables: degree of polarisation and polarisation angle, that can help discriminate between different models and understand the emission mechanism of the source.
In this thesis, we have used AstroSat-CZTI Compton interactions (double pixel events) for polarisation studies in 100 – 380 keV. We explored the utility of polarisation double pixel events to do spectroscopy above 100 keV and established it using Crab observations, which is the standard calibration source in the X-ray sky.
We have tried to comprehend the emission mechanism, geometry of the corona, and nature of the jet in Cygnus X-1 with the help of polarisation measurements and spectroscopy in the extended energy range of 20 - 380 keV. We further investigated the different hard X-ray spectral states in Cygnus X-1 and identified distinct accretion modes in the source based on the hard X-ray data and its polarisation dependence.
In this talk, I will discuss the implications of these results to understand the source. Further, I will show the necessity of the Compton spectro-polarimeter below 100 keV and discuss the conceptual design and related instrumentation to improve the sensitivity of the detector. |
