Abstract Details

Name: SUMAN BALA
Affiliation: SRF
Conference ID: ASI2021_332
Title : A possible physical explanation of the observed anharmonic ratio between the cyclotron line energies of Cep X-4
Authors and Co-Authors : Suman Bala, Research Scholar, Inter-University Centre for Astronomy and Astrophysics, Pune, India Dipankar Bhattacharya, Professor, Inter-University Centre for Astronomy and Astrophysics, Pune, India Jayashree Roy, postdoctoral fellow, Inter-University Centre for Astronomy and Astrophysics, Pune, India Varun Bhalerao, Professor, Indian Institute of Technology Bombay, Mumbai
Abstract Type : Oral
Abstract Category : Stars, ISM and Galaxy
Abstract : We present a physical explanation of the anharmonic ratio between the cyclotron line energies of Cep X-4 observed by Suzaku during 2014 outburst. In this work, we offer a theoretical framework for predicting cyclotron line shapes, assuming the presence of an accretion mound at the polar cap of the neutron star. The accretion mound is considered to be in a steady-state equilibrium supported by the magnetic field. The structure of the mound in magnetostatic equilibrium is solved numerically to obtain the matter density configuration and the magnetic field distribution. The local magnetic field at the mound surface is computed, which is then used to generate the expected cyclotron lines' profile. This is done for a range of mound masses and magnetic field strengths, all the computed profiles are then cast in the form of a Table Model, to be used for spectral fitting using the XSPEC software package. We have attempted fitting this model to explain the observed anharmonic ratio between the observed cyclotron line energies of Cep X-4. We have demonstrated that the observed anharmonic ratio can be explained either as a distorted fundamental line or two harmonics affected by the magnetic field distortion caused by the formation of an accretion mound at the polar cap. We find that the latter can better explain the observed feature in Cep X-4.