Rise and fall of silicate dust in RS Ophiuchi following the 2006 eruption

TL;DR

This study analyzes infrared observations of RS Ophiuchi after its 2006 eruption, revealing variable silicate dust features, atomic lines, and insights into dust properties and mass-loss rates in the system.

Contribution

It provides the first detailed analysis of silicate dust evolution in RS Ophiuchi post-eruption using archival Spitzer data, highlighting dust variability and grain peculiarities.

Findings

Silicate dust features are variable over time.

Dust emission indicates mass-loss rates of 1.0-1.7×10^{-7} M_sun/yr.

Longer wavelength feature peaks at 17 μm, suggesting unique grain properties.

Abstract

We present an analysis of archival Spitzer InfraRed Spectrograph (IRS) observations of the recurrent nova RS Ophiuchi obtained on several occasions, beginning about 7 months after the outburst in 2006. These data show atomic emission lines, absorption bands due to photospheric SiO, and the well known silicate dust features at $9.7\,\mu$m and $18\,\mu$m. The dust emission, arising in the wind of the secondary star, is fitted by Dusty models for mass-loss rates in the range $1.0-1.7\times10^{-7}$M$_{\odot}$yr$^{-1}$. The silicate features are similar in profile to those seen in circumstellar environments of isolated late-type stars and some dusty symbiotic binaries, although the longer wavelength feature peaks at $17\,\mu$m,, instead of the usual $18\,\mu$m, indicating peculiar grain properties. The dust features are variable, appearing stronger in 2006-2007 during outburst than in 2008-2009 when the system was in the quiescent state. This variability is attributed to changes in the ultraviolet output and the reformation of the accretion disk, although a decline in the mass-loss rate of the red giant secondary star could also play a role. Further observations, in the aftermath of the 2021 eruption, could provide a definitive conclusion.