The X-ray Evolution of the Symbiotic Star V407 Cygni during its 2010 Outburst

TL;DR

This study analyzes X-ray observations of V407 Cyg during its 2010 outburst, revealing the evolution of shock and white dwarf surface emissions, and proposes a model of blast wave interaction with the Mira wind.

Contribution

It introduces a simple model of blast wave-wind interaction that explains the X-ray evolution and constrains system parameters like binary separation and Mira mass loss rate.

Findings

Optically thin component brightened around day 20.

Binary separation likely larger than previously thought.

Mira's mass loss rate is probably lower than earlier estimates.

Abstract

We present a summary of Swift and Suzaku X-ray observations of the 2010 nova outburst of the symbiotic star, V407 Cyg. The Suzaku spectrum obtained on day 30 indicates the presence of the supersoft component from the white dwarf surface, as well as optically thin component from the shock between the nova ejecta and the Mira wind. The Swift observations then allow us to track the evolution of both components from day 4 to day 150. Most notable is the sudden brightening of the optically thin component around day 20. We identify this as the time when the blast wave reached the immediate vicinity of the photosphere of the Mira. We have developed a simple model of the blast wave-wind interaction that can reproduce the gross features of the X-ray evolution of V407 Cyg, and explore a parameter space of ejected mass, binary separation and Mira mass loss rate. If the model is correct, the binary separation is likely to be larger then previously suggested and the mass loss rate of the Mira is likely to be relatively low.