X-ray Modeling of \eta\ Carinae and WR140 from SPH Simulations

TL;DR

This paper uses 3D hydrodynamic SPH simulations to model X-ray emissions from colliding wind binaries ta Carinae and WR140, successfully reproducing most observed light curves and revealing complex post-periastron phenomena.

Contribution

It introduces improved SPH simulations with radiative cooling and wind acceleration to interpret X-ray observations of colliding wind binaries.

Findings

Simulations match RXTE light curves for most phases.

Discrepancies in periastron dips highlight modeling challenges.

Post-periastron bubbles affect X-ray emission in ta Carinae.

Abstract

The colliding wind binary (CWB) systems \eta\ Carinae and WR140 provide unique laboratories for X-ray astrophysics. Their wind-wind collisions produce hard X-rays that have been monitored extensively by several X-ray telescopes, including RXTE. To interpret these X-ray light curves and spectra, we apply 3D hydrodynamic simulations of the wind-wind collision using smoothed particle hydrodynamics (SPH), with the recent improvements of radiative cooling and the acceleration of the stellar winds according to a \beta\ law. For both systems, the 2-10 keV RXTE light curves are well-reproduced in absolute units for most phases, but the light curve dips associated with the periastron passages are not well matched. In WR140, the dip is too weak, and in \eta\ Carinae, the large difference in wind speeds of the two stars leads to a hot, post-periastron bubble that produces excess emission toward the end of the X-ray minimum.