Shell-Shocked: The Interstellar Medium Near Cygnus X-1

TL;DR

This study investigates the interstellar shell near Cygnus X-1 using multi-wavelength observations and shock models, constraining its properties and exploring potential origins such as jets or stellar winds.

Contribution

It provides detailed observational constraints and analysis to better understand the shockwave's nature and possible driving mechanisms near Cygnus X-1.

Findings

Shock speed less than a few hundred km/s

ISM density below 5 cm^-3

Power to drive shock < 2 x 10^38 erg/s

Abstract

We conduct a detailed case-study of the interstellar shell near the high-mass X-ray binary, Cygnus X-1. We present new WIYN optical spectroscopic and Chandra X-ray observations of this region, which we compare with detailed MAPPINGS III shock models, to investigate the outflow powering the shell. Our analysis places improved, physically motivated constraints on the nature of the shockwave and the interstellar medium (ISM) it is plowing through. We find that the shock is traveling at less than a few hundred km/s through a low-density ISM (< 5 cm^-3). We calculate a robust, 3 sigma upper limit to the total, time-averaged power needed to drive the shockwave and inflate the bubble, < 2 x 10^38 erg/s. We then review possible origins of the shockwave. We find that a supernova origin to the shockwave is unlikely and that the black hole jet and/or O-star wind can both be central drivers of the shockwave. We conclude that the source of the Cygnus X-1 shockwave is far from solved.