Expanding Bipolar X-ray Structure After the 2006 Eruption of RS Oph

TL;DR

This paper reports the detection and analysis of bipolar extended X-ray emission from RS Oph's 2006 eruption, revealing expansion dynamics and collimation mechanisms of nova ejecta over several years.

Contribution

It provides the first detailed measurement of the bipolar X-ray structure's expansion and confirms collimation of ejecta in recurrent nova RS Oph after eruption.

Findings

Extended X-ray emission detected 1254 and 1927 days post-eruption.

Lobe expansion rate of approximately 1.1 mas/day.

Expansion velocity estimated at 4600 km/s.

Abstract

We report on the detection and analysis of extended X-ray emission by the {\it Chandra} X-ray Observatory stemming from the 2006 eruption of the recurrent novae RS Oph. The extended emission was detected 1254 and 1927 days after the start of the 2006 eruption and is consistent with a bipolar flow oriented in the east-west direction of the sky with opening angles of approximately $70^{\circ}$. The length of both lobes appeared to expand from 1.3 arcsec in 2009 to 2.0 arcsec in 2011, suggesting a projected expansion rate of $1.1\pm0.1 {\rm ~mas~day}^{-1}$ and an expansion velocity of $4600\ {\rm km~s}^{-1}\ (D/2.4\ {\rm kpc})$ in the plane of the sky. This expansion rate is consistent with previous estimates from optical and radio observations of material in a similar orientation. The X-ray emission does not show any evidence of cooling between 2009 and 2011, consistent with free expansion of the material. This discovery suggests that some mechanism collimates ejecta away from the equatorial plane, and that after that material passes through the red-giant wind, it expands freely into the cavity left by the 1985 eruption. We expect similar structures to arise from latest eruption and to expand into the cavity shaped by the 2006 eruption.