Studying cyclotron lines in HMXBs using Astrosat-LAXPC
Date & Time :
Auditorium and zoom
Neutron Stars in High-Mass X-ray binaries have very high magnetic field strengths of ~1012 G. At such high magnetic fields, Quantum Electro-Dynamical (QED) effects become important in particle interactions. One such effect is the modification of the scattering cross-section of photons with electrons. This is manifested as a broad absorption feature in the spectra of these systems known as Cyclotron Resonance Scattering Feature (CRSF) or Cyclotron Line. Cyclotron lines can become an important tool to understand the accretion and magnetic field geometry in these systems. Large Area X-ray Proportional Counter (LAXPC) onboard Astrosat has a very large effective area and moderate resolution spectroscopic ability, is just the right instrument to study cyclotron lines. In this talk, I will discuss the observational works related to cyclotron lines using data from AstrosatLAXPC. For two HMXBs, 4U 1538-52 and 4U 1907+09, we have studied the detailed pulse phase resolved behavior of cyclotron line parameters. This was possible thanks to the large effective area of LAXPC. In another work, we have detected the cyclotron line in HMXB source IGR J19294+1816 during its type-I outburst in October 2019. I will also discuss recent work on the time evolution of cyclotron line seen in Hercules X-1 using many high energy instruments including Astrosat-LAXPC.
About Speaker :
Varun is currently a postdoctoral fellow at ARIES, Nainital.