LIFELINE: The program for the simulation of the X-ray line profiles in massive colliding wind binaries

TL;DR

LIFELINE is a self-consistent computational tool for simulating X-ray line profiles in massive colliding wind binaries, aiding the interpretation of future high-resolution X-ray observations to characterize stellar winds.

Contribution

The paper introduces LIFELINE, a novel program that models X-ray line profiles considering wind interactions, radiation pressure, and gravity, for a wide grid of binary systems.

Findings

Line profiles in adiabatic regions are simple.

Radiative regime profiles are more complex due to the Coriolis effect.

Significant differences in line morphology depend on wind properties.

Abstract

The study of the X-ray line profiles produced by massive colliding wind binaries is a powerful tool for the characterisation of the stellar winds. We built a self-consistent program for the computation of line profiles named LIFELINE. The resulting theoretical profiles can be compared to the line profile that will be observed with future high-resolution X-ray spectrographs to retrieve the characteristics of the stellar winds generating them. We considered a grid of 780 O-type binaries and computed, for each of them, the wind velocity distribution of each star, taking the impact of the radiation pressure and gravity force of the companion star into account. We then computed the characteristics of the wind shock region and followed the emitted photons towards the observer to compute their absorption. Finally, the Fe K line profiles near 6.7keV were constructed from the distribution of the photons as a function of the radial velocities of their emitting region. LIFELINE can be used to compare the theoretical line profiles to the observed ones or to compute theoretical profiles for a new binary system. We highlight the results for three systems. While the line profiles created in adiabatic wind collision regions are quite simple, the line profiles arising from regions in the radiative regime, as found in short-period binaries, are more sophisticated notably because of the Coriolis effect on the shape of the shock. The predicted differences in line morphology between systems with different wind properties are quite significant, allowing a detailed comparison between the theoretical profiles and those that will be observed with future high-resolution X-ray spectrometers.