Monte Carlo Simulations of Thermal Comptonization Process in a Two Component Advective Flow around a Neutron Star

Abstract

We explore spectral properties of a Two-Component Advective Flow (TCAF) around a neutron star. We compute the effects of thermal Comptonization of soft photons emitted from a Keplerian disc and the boundary layer of the neutron star by the post-shock region of a sub-Keplerian flow, formed due to the centrifugal barrier. The shock location $X_s$ is also the inner edge of the Keplerian disc. We compute a series of realistic spectra assuming a set of electron temperatures of the post-shock region $T_{CE}$, the temperature of the normal boundary layer (NBOL) $T_{NS}$ of the neutron star and the shock location $X_s$. These parameters depend on the disc and halo accretion rates ($\dot{m_d}$ and $\dot{m_h}$, respectively) which control the resultant spectra. We find that the spectrum becomes harder when ${\dot{m}}_h$ is increased. The spectrum is controlled strongly by $T_{NS}$ due to its proximity to the Comptonizing cloud since photons emitted from the NBOL cool down the post-shock region very effectively. We also show the evidence of spectral hardening as the inclination angle of the disc is increased.

28 pages, 14 figures, 1 table

References in corpus (12)

• Evaluating Spectral Models and the X-ray States of Neutron-Star X-ray Transients
• Average hard X-ray emission from NS LMXBs: Observational evidence of different spectral states in NS LMXBs
• A new Comptonization model for low-magnetized accreting neutron stars in low mass X-ray binaries
• Estimation of Mass of Compact Object in H 1743-322 from 2010 and 2011 Outbursts using TCAF Solution and Spectral Index - QPO Frequency Correlation
• A dichotomy between the hard state spectral properties of black hole and neutron star X-ray~binaries
• The 2004 Outburst of BHC H1743-322: Analysis of spectral and timing properties using the TCAF Solution
• Short-Term Variability of X-rays from Accreting Neutron Star Vela X-1: I. Suzaku Observations
• X-ray spectral and timing behavior of Scorpius X-1. Spectral hardening during the flaring branch
• Temporal variability from the two-component advective flow solution and its observational evidence
• Segregation of a Keplerian disc and sub-Keplerian halo from a Transonic flow around a Black Hole by Viscosity and Cooling processes
• Monte-Carlo Simulations of Thermal Comptonization Process in a Two Component Accretion Flow Around a Black Hole in presence of an Outflow
• High Energy Radiation from Neutron Star Binaries

Cited by in corpus (4)

• Timing Properties of Shocked Accretion Flows around Neutron Stars in Presence of Cooling
• Two-Component Advective Flows around Neutron Stars
• A Unified Spectral Model for Accreting Neutron Stars
• Generalized Flows around Neutron Stars